Diagnosing Big Boy control board #6

[amphi_sc]

I have a suspicion my #6 Big Boy control board is acting up.  The Big Boy itself is clean internally but cold.  When driving after a few hours I can see the house batteries drop ... example to 12.2 and chassis bats are 13.3 with engine running.  No green light on PCB #6.  I press the boost switch and BB clicks and both banks measure about 12.8 to 12.9 and about 50 amps going into the house ( BTW, I don't hold the boost for more than a minute).  After a days driving and then plugged into shore Magnum may be bulk charging the house at 14.1 and chassis at 12.6.( again no green led on #6) press the boost switch and chassis gets an appropriate charging voltage.  Both 7.5 amp fuses on board #6 test good.  I've unplugged & replugged both edge connectors in case they were dirty.  No LEDs on  board #6 light up.

I know Frank is capable of working on this board as indicated by his many posts and test jig such as in thread 

What can I test to verify the problem is with the board and not upstream of the board? And I'm on the road moving every 3-5 days so pulling the board and sending it off isn't doable for a couple of months.  I can likely limp through this "vacation" by running the generator on long driving days and the chassis shouldn't run down too much in 5 days.  But if there's some diagnostics I can do on the road it would be nice to try.

Thanks 

BTW, putting in a ML-ACR could be a solution after I get home in the fall, but that's a long time..

Edited June 23, 2024 by amphi_sc

[klcdenver]

For a band aid fix you can get a pair of jumper cables and tie the house and chassis batteries together to keep from running generator.

[Frank McElroy]

If you haven't seen it, here is a video of how the circuit board works in terms of which LEDs light based on the remote switch functions for the battery disconnect (salesman switch) and battery boost (iso relay switch).

For the LEDs to light the ignition switch must be turned ON.  If the two fuses are good the two red LEDs will light up.  If the circuit board is detecting that both battery cutoff switches are turned ON, then the lower green LED will be ON.  If this LED is not ON, the board is thinking that one of the battery cutoff switches are turned OFF and it will not energize big boy.

[Dr4Film]

Do a temporary jumper to keep the batteries fully charged while driving. Then when parked and hooked to shore or generator power, use a small 5 amp portable 120 VAC battery charger to keep your chassis batteries fully charged. Make sure to plug it into an outlet powered by your inverter.

My coach came with a small battery charger in the battery compartment that some previous owner installed. So obviously something must not be right with the charging circuits. It will be removed once I have the Blue Seas ML-ACR fully installed.

[amphi_sc]

Just a short update.  At this point I think part of the 12v system isn't kicking in although most of it is!  So far I've only seen the BigBoy not automatically kicking in AND the Aqua hot "furnace" blowers not coming on. All lights, Aqua Hot electric and diesel, fantastic fans, mascerator pump and toilet, water hose & elec cord reel and everything else 12v I've tried seems to be working normally.  Been trying to look at the schematics for something in common with the BB control board 6 12 volt detection & Aqua Hot blowers but nothing jumping out me yet, but I'll keep digging.i have cycled the salesman switch a couple of times and both battery disconnects.  It won't be raining so much tomorrow so maybe I can probe around some more. 

However I have noticed something even weirder.  Sun came out for a while and solar exceeded 12 v demand thus Magnum went from float charge to 'full charge' so both banks of batteries settled at 12.8.  After the sun went down and some light use the Magnum went back to Float charge but this is interesting; House went to 13.4 and chassis climbed to 13.0 but BigBoy not engaged and when I press the Bat Boost switch I hear the BB click and house drops from 13.4 to 13.3 - chassis climbed from 13.0 to 13.3.  release the boost and drops back to 13.0.  Bit why would the chassis battery have climbed from 12.8 to 13.0 after the sun went down without the BB combining the banks?  Is there some cross feed happening somewhere? Gotta dig more... especially with the hot water heat blowers acting weird.

And thanks to Frank for the video, very helpful.

[Tom Cherry]

6 hours ago, amphi_sc said:

Just a short update.  At this point I think part of the 12v system isn't kicking in although most of it is!  So far I've only seen the BigBoy not automatically kicking in AND the Aqua hot "furnace" blowers not coming on. All lights, Aqua Hot electric and diesel, fantastic fans, mascerator pump and toilet, water hose & elec cord reel and everything else 12v I've tried seems to be working normally.  Been trying to look at the schematics for something in common with the BB control board 6 12 volt detection & Aqua Hot blowers but nothing jumping out me yet, but I'll keep digging.i have cycled the salesman switch a couple of times and both battery disconnects.  It won't be raining so much tomorrow so maybe I can probe around some more. 

However I have noticed something even weirder.  Sun came out for a while and solar exceeded 12 v demand thus Magnum went from float charge to 'full charge' so both banks of batteries settled at 12.8.  After the sun went down and some light use the Magnum went back to Float charge but this is interesting; House went to 13.4 and chassis climbed to 13.0 but BigBoy not engaged and when I press the Bat Boost switch I hear the BB click and house drops from 13.4 to 13.3 - chassis climbed from 13.0 to 13.3.  release the boost and drops back to 13.0.  Bit why would the chassis battery have climbed from 12.8 to 13.0 after the sun went down without the BB combining the banks?  Is there some cross feed happening somewhere? Gotta dig more... especially with the hot water heat blowers acting weird.

And thanks to Frank for the video, very helpful.

The SIMPLE thing, as Richard pointed out, is to just JUMPER.  The easiest is a auto jumper cable between the Positives of the House and Chassis.

Frank and I both "Jumper" while in storage. We both disconnect (or at least I do...) the signal to the Big Boy so that it is not engaged for the solenoid coil to be off. I use a Jumper that I made up which is a #2 AGW cable.  Frank has fabricated a copper tubing jumper that he puts on the Big Boy.  The result is the same.  Both banks are being charged when driving.  Both banks are being charged when on shore/genny. 

The Leece Neville Alternator's Voltage regulator really doesn't care how many batteries are in the Chassis circuit.  It will charge them within the normal limits...so there is NO OVERCHARGING.  Same deal for the House on AC/Genny. The Magnum will be controlling the charging, so there is NO OVERCHARGING.  We have seen folks that put on cheap chargers on one bank or the other and left them for extended periods of time and actually "toasted" one or the other. Same deal for a big auto charger. 

The Leece Neville regulator and the Magnum 3 stage charger will protect and not overcharge.  NOW...the one Caveat...  This assumes that both banks are in reasonable condition and that they don't have bad internal cells and that the Specific Gravity is OK in each cell.

The easiest way to know if the Big Boy is working...  LISTEN, FEEL & Measure.

Unplug from Shore...  Let the house bank (use the Aladdin or the Magnum remote) run down to about 12.3 or so.  Run fans or watch TV or whatever.  THEN,  turn OFF the Pedestal breaker.  Plug back in.  Turn on the breaker...and walk to the RRB.  You should here a CLUNK which means that board 6 has "taken over".  Then the Big Boy will start to make noise. It is loud.  You can hear it.  After a while, then the can should get HOT.  When it is working and the House is down (or the Chassis), eventually, the Can on the Big Boy will be so hot, you can NOT keep your hand wrapped around it.

THIS IS NORMAL.  NOTE...for Camelot owners reading and saying.... HEY, will that work....The answer is YES...except the Big Boy will be much quieter and will get less hot...and you can hold your hand on it...it is HOT, but not burning hot.  Reason is simple.  The Dynasty is providing a regulated voltage to the coil...around 8 VDC. The Camelot's BIRD Module is different...the voltage is lower....should be around 4 but typically runs in the mid 3's.

NOW...if the Big Boy (Dynasty) is hot and making a vibrating or humming noise....then check the voltage on each Bank. The voltage should be within 0.1 to 0.2 VDC.  IF you can measure the studs on the Big Boy or find the other ends of the cable, then use your VOM and the voltage across the studs should be close to zero.

If all that works...  FINE...things are well.  If their are "WEIRD" things...like the House jumping around and the Big Boy is engaged or all of a sudden it drops out...

HOUSE BATTERIES need to be tested.  That is easy to do, even in the Field. After the House shows FULL or Float Charge....  Turn off AC power and also disconnect or cover Solar.  USE THEM...when the Magnum remote shows 12.6 or so...  Turn OFF both disconnect switches.  Then remove the Jumpers on the House Banks...  Then measure the Voltages of each Battery.  They ALL should be around 12.6 or so...or all the same.  A 0.2 VDC difference in one battery....that one is an issue.  

Then, the Specific Gravity needs to be checked.  Amazon will ship anywhere...assuming you don't have one on board....many of us carry them.  I compiled and also wrote several sections of this.  You need a Hydrometer and this one works and also can be "tested".  It is very accurate... Put the following in the Amazon search box...

Even ONE cell, which has a LOW Specific Gravity will act like a RESISTOR...and that Battery will not allow the other one to be charged.  REAL WORLD.  I have 4.  The original Interstates would not perform. I then did the tests and also LEARNED (by reading and also DOING) about batteries...and Frank coached me some. I had ONE house with a shorted cell.  EASY to spot...the voltage was 4.6 VDC.  BUT, I had another that seemed OK.  OPPS...when I used a Hydrometer...One cell in another battery was almost TOAST.  Not shorted (which would have dropped the voltage to 4.6 or so).  SO, in effect.  By luck of the draw.  I had my TWO OK batteries paired up with a giant resistor.  I swapped and then had BOTH good batteries in the same series...I did NOT put a jumper on the other two. That worked fine, I ran that for a while and decided to put in NEW Trojans

 

 

EZRED SP101 Battery Hydrometer, Factory

 

As to converting and quasi gutting the charging system....that depends on your skill set. If you can do it and understand how....then have at it. BUT, if you have to pay someone and hopefully, THEY know enough about the Dynasty system (and we have SCADS that do here) then it might make sense. I THINK and Frank might chime in. The board 6 also controls the Towed (TOAD) vehicle charging system, so if your abandon board 6 or it needs to be fixed, then you will have to add in a relay and rewire the charging system to your 7 pin...assuming that you use that. Not a big deal...but one MUST totally understand all the circuits.

This is "Generally" CookBook Electonics...but one should know how the circuits work and be able to read prints and fully understand....otherwise...???

Good Luck...hope this keeps you on the road and a bit less stressed...

[Frank McElroy]

6 hours ago, amphi_sc said:

Just a short update.  At this point I think part of the 12v system isn't kicking in although most of it is!  So far I've only seen the BigBoy not automatically kicking in AND the Aqua hot "furnace" blowers not coming on. All lights, Aqua Hot electric and diesel, fantastic fans, mascerator pump and toilet, water hose & elec cord reel and everything else 12v I've tried seems to be working normally.  Been trying to look at the schematics for something in common with the BB control board 6 12 volt detection & Aqua Hot blowers but nothing jumping out me yet, but I'll keep digging.i have cycled the salesman switch a couple of times and both battery disconnects.  It won't be raining so much tomorrow so maybe I can probe around some more. 

However I have noticed something even weirder.  Sun came out for a while and solar exceeded 12 v demand thus Magnum went from float charge to 'full charge' so both banks of batteries settled at 12.8.  After the sun went down and some light use the Magnum went back to Float charge but this is interesting; House went to 13.4 and chassis climbed to 13.0 but BigBoy not engaged and when I press the Bat Boost switch I hear the BB click and house drops from 13.4 to 13.3 - chassis climbed from 13.0 to 13.3.  release the boost and drops back to 13.0.  Bit why would the chassis battery have climbed from 12.8 to 13.0 after the sun went down without the BB combining the banks?  Is there some cross feed happening somewhere? Gotta dig more... especially with the hot water heat blowers acting weird.

And thanks to Frank for the video, very helpful.

Aquahot may be in a low battery lockout mode.  To reset, press the reset button on the aquahot control board.

With the ignition ON, please post a picture of PCB#6 so I can see which LEDs are lit.

[amphi_sc]

10 minutes ago, Frank McElroy said:

Aquahot may be in a low battery lockout mode.  To reset, press the reset button on the aquahot control board.

The Aquahot heats water fine on either electric or diesel (and cycles normally) but you think a reset would affect the furnace blower registers???  The thermostats indicate the zone is calling for heat.  I would have thought the Aquahot control box is fine but some bigger common breaker or relay isn't passing 12v to the BigBoy 12v sensing circuit as well as 12v to the hot water furnace circuit blowers. 

In paying closer attention to a symptom I seem to recall that previously even when not on shore power turning the chassis battery disconnect back on I used to hear an immediate "thump" from toward the rear of the coach but I didn't it hear today ... leading me to think some other relay isn't getting powered.  

[Tom Cherry]

25 minutes ago, amphi_sc said:

The Aquahot heats water fine on either electric or diesel (and cycles normally) but you think a reset would affect the furnace blower registers???  The thermostats indicate the zone is calling for heat.  I would have thought the Aquahot control box is fine but some bigger common breaker or relay isn't passing 12v to the BigBoy 12v sensing circuit as well as 12v to the hot water furnace circuit blowers. 

In paying closer attention to a symptom I seem to recall that previously even when not on shore power turning the chassis battery disconnect back on I used to hear an immediate "thump" from toward the rear of the coach but I didn't it hear today ... leading me to think some other relay isn't getting powered.  

OK...go back and read my POST.  If you NEVER hear the CLUNK...then the Board 6 is BAD OR your batteries "THINK" that they are full charged..  I outlined an easy way to test the board and the Big Boy.  Do that... You need to understand that and how to test and verify the Big Boy as well as the Condition of your Batteries.  On and OFF Clunking is NOT something that happens...unless there is an issue.

The BIg Boy (the CLUNK) will happen a few minutes, usually, after you apply shore...and rarely SHUT OFF or Disengage.  WHY? All your interior lights and fans and pump are DC. You are DRAINING down the House Bank.  So the Magnum is charging....and usually it will stay engaged to keep the Chassis up. You DO have a Parasitic load on the Chassis...even though you are NOT running the engine.  Some of the up front devices, like the shades on mine, are CHASSIS powered.  So, you are always pulling some DC for something.  THEN, in effect, the Big Boy will be or should be 100% ENGAGED...operating as I stated....HOT and Humming...

As to the Aquahot.  Frank is correct.  If the Low Voltage LIGHT is on...use a plastic straw (like a mixed cocktail ) or a small wooden dowel and push in the reset button on the AH unit...per the instruction. 

NOW... the way the Aquahot works, you have WAY MORE devices that pull "power" and if your interior devices such as the Fantastic Fans and the water pump are all working, then you probably don't have any major issue...other than....the House Bank is NOT getting charged. The 120 VAC electric is ONLY used for the heating element.  All the rest of the Aquahot is 12 VDC.  The Stirring Pump (on when running the diesel or such) is 12 VDC. The Zone Pump (that circulates the antifreeze to a particular zone is 12 VDC.  The blower(s) on the heat exchangers are 12 VDC.

Trouble shoot the Board 6.  It HAS to work as outlined.  If NOT then you will not keep the House or Chassis charged. Do NOT just SAY... I GOT GOOD BATTERIES.  You have to TEST THEM. 

SO, drain down the house some....12.4 or 12.5 is NOT running them down to oblivion.  THEN with NO AC ON....follow the Startup Step and if you don't hear CLUNK....then either the COIL is dead (a rarity...but it DOES happen) or Board 6 is bad. FWIW...  You can follow the Temporary Jumpering of the Banks and send Paul Whittle or Frank McElroy the Board and they can repair it and their turn around...assuming they have no other projects going on, is short.  THEN you will be OK and can continue your trip. I have parts shipped in all over the US as I travel....thing BREAK or a GC loses something or breaks something...  LOL.

Read my post.  Then test..  Then contact Frank or Paul if the board is bad... 

Hope this makes sense...

[amphi_sc]

I'm leaning heavily toward board 6 as the problem.  As I expected, pushing the reset button on the Aquahot did NOT make the BigBoy engage.  However using Frank's video as an example, ignition on and then both red LEDs did light up and the green one at the bottom.  Pushing the test switch for the 12v disconnect did flip the latching solenoid off, however holding it for 3-5 seconds only made that relay click on/off & flash the other led.  I had to use the salesman switch up front to restore 12v power.  After restoring 12v power using the salesman switch the board mounted test switch could turn it off again, but still never fully latch it back on.  The other switch for testing the BigBoy does nothing.... No thunks, no green LEDs. There is 12v to one side of the BB coil, hard to measure the rear coil terminal. Using the boost switch on.the dash will close the BigBoy and gets a 0 to  0.1 volt drop across the BigBoy terminals.  Holding the boost switch down for minute and I can see the house voltage drop and chassis rise until they are essentially the same.  Start the engine and then hold the Boost down for a minute and the chassis voltage drops slightly and the house rises as it accepts a charge. Seems to me that implies the BB itself is okay but the control board isn't controlling it properly.

BTW, after a day's driving and then running the generator for an hour during supper and then shutting it down to quietly watch a couple hours of TV with a residential fridge and also basement freezer running probably a 85% duty cycle maintaining a slightly below 0° measured freezer temp, in the morning the house batteries would measure 12.1 and chassis 12.5 I so don't believe the AGMs are toasted.  No way I know of to measure specific gravity.

To get by for the next 5 months (which includes some on and off boondocking and moving every 3-5 days) I'll Velcro in a temporary switch in the battery compartment to easily connect or disconnect the two banks.  I don't want to be flipping both battery disconnects off while getting tools out every couple days to jump or unjump the BB terminal with the side effects of rebooting or unstable power to the multiplex computer in the process.  Maybe in November Frank or Paul could be able to look at board #6 while the RV is in storage for about a month before the next trip for the Thanksgiving Christmas holidays.

In the last couple of months while driving I did notice the house battery voltage rise to alternator voltage for a while and then drop to 12.6 for a while and then back to 13.2, and then back to 12.6 again for a spell.  I bet that was trying to tell me board #6 was getting flakey, and it has now finally given up.

[Tom Cherry]

7 hours ago, amphi_sc said:

I'm leaning heavily toward board 6 as the problem.  As I expected, pushing the reset button on the Aquahot did NOT make the BigBoy engage.  However using Frank's video as an example, ignition on and then both red LEDs did light up and the green one at the bottom.  Pushing the test switch for the 12v disconnect did flip the latching solenoid off, however holding it for 3-5 seconds only made that relay click on/off & flash the other led.  I had to use the salesman switch up front to restore 12v power.  After restoring 12v power using the salesman switch the board mounted test switch could turn it off again, but still never fully latch it back on.  The other switch for testing the BigBoy does nothing.... No thunks, no green LEDs. There is 12v to one side of the BB coil, hard to measure the rear coil terminal. Using the boost switch on.the dash will close the BigBoy and gets a 0 to  0.1 volt drop across the BigBoy terminals.  Holding the boost switch down for minute and I can see the house voltage drop and chassis rise until they are essentially the same.  Start the engine and then hold the Boost down for a minute and the chassis voltage drops slightly and the house rises as it accepts a charge. Seems to me that implies the BB itself is okay but the control board isn't controlling it properly.

BTW, after a day's driving and then running the generator for an hour during supper and then shutting it down to quietly watch a couple hours of TV with a residential fridge and also basement freezer running probably a 85% duty cycle maintaining a slightly below 0° measured freezer temp, in the morning the house batteries would measure 12.1 and chassis 12.5 I so don't believe the AGMs are toasted.  No way I know of to measure specific gravity.

To get by for the next 5 months (which includes some on and off boondocking and moving every 3-5 days) I'll Velcro in a temporary switch in the battery compartment to easily connect or disconnect the two banks.  I don't want to be flipping both battery disconnects off while getting tools out every couple days to jump or unjump the BB terminal with the side effects of rebooting or unstable power to the multiplex computer in the process.  Maybe in November Frank or Paul could be able to look at board #6 while the RV is in storage for about a month before the next trip for the Thanksgiving Christmas holidays.

In the last couple of months while driving I did notice the house battery voltage rise to alternator voltage for a while and then drop to 12.6 for a while and then back to 13.2, and then back to 12.6 again for a spell.  I bet that was trying to tell me board #6 was getting flakey, and it has now finally given up.

Fundamentals....

If, after you run down the Batteries to the levels you posted, then plug into AC (or start Genny) and you don't hear the CLUNK... Board #6 is NOT working.  Then, obviously it would not get HOT. When you ran the genny, you should have put your hand and your ear near the Big Boy. If the Big Boy is Humming or making a fuss, then the Big Boy is energized. It should be, after an hour or so, based on the condition of your batteries, HOT to the touch.

I did not pick up you have AGM's.  BUT, the SAME rules apply for AGM's as far as shorted cells.  Shorted cells are MORE of an issue or concern in AGMS...as you CANNOT replenish. 

SO... Simple test. After the AGM's are charged or even partially recharged...then KILL House Switch. Disconnect the Jumpers.  Wait about 10 minutes or so.  Measure the batteries.  ASSUMING you don't have one that is in the 4.X range, then all the batteries should be within 0.1 VDC of each other.  If they vary more than that, then they may not be TOAST...but they are NOT GOOD. 

Now, the ONLY WAY to test them.... Do the Discharge Test.  You were partially there when you measured them. IF they were at 12.1 or so, that is a good drawdown...not perfect.  SO, recharge them...driving or Genny.  When the Magnum says FLOAT....they are recharged.

NOW...  SIMPLE.  USE a little DC juice...  When the batteries drop to around 12.7 or so....then Turn OFF disconnect.  Then pull the Jumpers.  Then wait 10 - 20 minutes. Measure the Voltage.  Look at the CHART.  IF they ARE OK (not Toast), then the voltages should be almost the same....no more than 0,1 VDC difference in the bank.  IF NOT....then they have some internal issues.  Cells are different. IF you tore them apart, you would see the Specific Gravity is different.  ODDS ARE..  one cell is bad.

You can't "SAY" batteries are OK...until you know how they recharge and then use the chart to check SOC. You can't take them to a shop and have them put on a tester. The carbon pile or cheap testers do NOT WORK on Deep Cycle.

You need information and you need to follow the requests so we can help you.  All we know now..., your Chassis Batteries are NOT BEING recharged.  They should be higher than 12.5.  They should be around 12.7 or so. And whether or not you have GOOD AGMs can't be determined until you test them.

Do the above....then we can help...but right now...  I can't do much.  Maybe Frank can...but all I know....is that I don't know if the Big Boy is going CLUNK and buzzing and getting HOT.  If it ain't then Board 6 ain't working... 

[Tom Cherry]

BTW.  When you used the word..  LATCHING...  I did not know you were referring to the BIG BOY or the Salesman (Battery Cutoff) Solenoid.  

The BIG BOY is NOT a latching SOLENOID (these are SOLENOIDS and NOT relays).  It is ONLY "ON" or working when there is a Pulsed or Voltage Controlled signal (OK...when the BOOST is used...it is FULL 12 VDC). 

The Salesman Solenoid or Battery Cutoff is a LATCHING style.  TOTALLY different.  There is NO continuous control signal. When you PUSH the spring loaded BATT CUT OFF switch, it sends a signal to the Solenoid.  Depending on WHICH way you pushed it...  UP OR DOWN, then the Coil "LATCHES IN" the contacts. SO, you have to TURN IT ON or OFF...and there is NO more control circuit voltage to the coil terminals.

The BIG BOY is an MUST HAVE A SIGNAL ( VDC ) to stay energized.  That is why Board 6 only send one when the batteries need to be connected....or when you use as a boost. NO SIGNAL....no COIL ENERGIZED....NO CONTCT CLOSURE.

You may know the difference....but others might not...so all learn...

 

[Frank McElroy]

12 hours ago, amphi_sc said:

I'm leaning heavily toward board 6 as the problem.  As I expected, pushing the reset button on the Aquahot did NOT make the BigBoy engage.  However using Frank's video as an example, ignition on and then both red LEDs did light up and the green one at the bottom.  Pushing the test switch for the 12v disconnect did flip the latching solenoid off, however holding it for 3-5 seconds only made that relay click on/off & flash the other led.  I had to use the salesman switch up front to restore 12v power.  After restoring 12v power using the salesman switch the board mounted test switch could turn it off again, but still never fully latch it back on.  The other switch for testing the BigBoy does nothing.... No thunks, no green LEDs. There is 12v to one side of the BB coil, hard to measure the rear coil terminal. Using the boost switch on.the dash will close the BigBoy and gets a 0 to  0.1 volt drop across the BigBoy terminals.  Holding the boost switch down for minute and I can see the house voltage drop and chassis rise until they are essentially the same.  Start the engine and then hold the Boost down for a minute and the chassis voltage drops slightly and the house rises as it accepts a charge. Seems to me that implies the BB itself is okay but the control board isn't controlling it properly.

BTW, after a day's driving and then running the generator for an hour during supper and then shutting it down to quietly watch a couple hours of TV with a residential fridge and also basement freezer running probably a 85% duty cycle maintaining a slightly below 0° measured freezer temp, in the morning the house batteries would measure 12.1 and chassis 12.5 I so don't believe the AGMs are toasted.  No way I know of to measure specific gravity.

To get by for the next 5 months (which includes some on and off boondocking and moving every 3-5 days) I'll Velcro in a temporary switch in the battery compartment to easily connect or disconnect the two banks.  I don't want to be flipping both battery disconnects off while getting tools out every couple days to jump or unjump the BB terminal with the side effects of rebooting or unstable power to the multiplex computer in the process.  Maybe in November Frank or Paul could be able to look at board #6 while the RV is in storage for about a month before the next trip for the Thanksgiving Christmas holidays.

In the last couple of months while driving I did notice the house battery voltage rise to alternator voltage for a while and then drop to 12.6 for a while and then back to 13.2, and then back to 12.6 again for a spell.  I bet that was trying to tell me board #6 was getting flakey, and it has now finally given up.

The two buttons on that PCB will remotely perform the same functions as the battery boost and salesman switches up front.  Older boards didn't have the 3 second delay to operate the battery disconnect.  So, a monetary press would cycle the function of the salesman switch.  For the dash switches to work but the push buttons on the board not to work could just be dirty contacts on the PCB switch buttons or a failed board component that generates the modulated ground signal to the big boy.  So, not seeing a green light when the battery iso button is pressed is likely a failed board component.

Both terminals on the big boy coil always sit at 12 volts.  The terminal most easy to access is pulsed between 12 volts and ground via the PCB circuit.  That's what will energize the big boy coil since the other terminal is at 12 volts.  When battery boost is pressed, this terminal is grounded and not pulsed.

[amphi_sc]

After many months on the road we have arrived home.  To get by over the summer I installed a simple battery cutoff switch and cables directly connecting the banks in the battery bay as that door is easy to open to rotate the new interconnecting switch as needed.  But now I want to address a better solution.

Restating the symptoms:

Salesman remote switch works as expected

Dash battery boost switch WILL engage the Big Boy relay and the voltages across the Big Boy will equalize.  i.e. I can let the batteries discharge for a few hours and then plug into shore power.  The Magnum starts bulk charge of the house at 14+ volts and even after several minutes the #6 board has not engaged the Big Boy and the chassis is at 12.5-12.6. BUT when I manually toggle the battery boost I hear the Big Boy "clunk" and chassis immediately comes up to 14+ volts.  So the Big Boy is internally clean and electrically the coil works.

With ignition switch on I see 2 red LEDs and one green LED.  Pressing the isolation button on the board does nothing:

 

So I'm leaning towards a problem with a component on the board.  Perhaps the relay on the board?  Several years ago I had an identical relay go "weak" that randomly killed power to my ECM so maybe the relay contacts have arc'd/pitted?  Just speculating at this point...it could be some other component on the board.

Some possible options:

1. Maybe Frank could look at/repair the board if I could mail it to him?????

2. Don't mess with anything and continue to flip my added interconnecting battery bank switch.  Down side is that as it parallels the 2 banks in the battery compartment vs interconnecting in the Rear Run Box Big Boy, the Aladdin will not show house charge amps from the alternator as I drive.

3. Use a Blue Sea ML-ACR someplace.  The RRB is pretty packed to where to mount it and cable size is unknown.   Would I need 4/0 from where the BB ties in to the ML-ACR? Picture of RRB:

 

As the Big Boy dash battery boost toggle switch works, if I left in the Big Boy then I wouldn't need to run wires to the dash for the new ML-ACR lighted switch.  On the other hand, would the ML-ACR fit where the Big Boy is? But then again running the extra wires to the front and tying it into the two copper tabs.  Third option is forget the extra wires and leave my work around manually interconnecting switch in the battery box as my emergency boost option.

Opinions please.

Thanks

 

[Tom Cherry]

First STEP….  @Frank McElroy will or has, depending on his personal time constraints….help you.

PM him.  He can tell you, usually over the phone, the quick and easy steps for testing. That MUST be done prior to any other action.

You can also search here.  The procedure for “manually” testing the big Boy is simple.  Then you test to see if the big Boy is getting the signal from board #6.  I don’t know the lights and such…but you can use a VOM.  
 

That will also tell you if the contacts in the big Boy are pitted or need cleaning….as well as if the coil is OK.  There is a cleaning procedure in the files.  Use SEARCH. Intellitec is key word. Click on EVERYWHERE.  Select files.  It will be there to download.

[Dr4Film]

My recommendation is to install the ML-ACR first to replace the Big Boy and its control board. Then you can decide later whether you want to install the remote switch somewhere in your dash area. Some have actually taken the Bat Boost Switch out and replaced it with the remote switch. I installed mine below the dash as it was almost impossible to get to the Bat Boost switch where it is presently located. I may be able to get to it if I remove the driver's seat from the floor. But that would be at the bottom of my to-do list.

The ML-ACR will go in right where the Big Boy is now, then you will need some copper bars configured to make the same connections that the Big Boy uses.

Here is an excellent thread by Paul Whittle who had installed the ML-ACR in basically the same location as yours. There are photos to help with understanding exactly how he accomplished the task.

https://www.monacoers.org/topic/1583-ml-acr-to-replace-big-boy-or-diode-isolatorlambertbattery-boost-relay/#comment-12122

Here is one thread you should also read.
https://www.monacoers.org/topic/8407-update-and-important-information-on-blue-seas-ml-acr-and-installation-requirement/#comment-88080

 

[amphi_sc]

I'm finally able to post a follow-up on my installation of the ML-ACR versus repair of the #6 board.

I chose a Blue Sea 7622 ML-ACR.  It has the manual override knob I thought I wanted and had a remote switch I really wasn't sure about at the time.  Now to shoe horn it in where the Big Boy was:

It's pretty tight in there!  Yes it will fit with just a bit of customization: (note, this photo does not show the final connections to the ML-ACR pigtail.  It was as a work-in-progress testing the operation, thus only a single ground wire stubbed in.  I had/have spare mate-n-lock stuff from when I reworked my trailer charge line):

I made two steel brackets, one for each side for the two attachment bolts of the Big Boy.  Not sure I'd get it perfect the first time so I left each side independent of the other side.  Two holes to screw the original bolts through and then welded a bolt (so it wouldn't have a turning problem putting a nut on the outside) on each bracket at the upper end to rest the ML-ACR on.  Slightly enlarged the top ML-ACR holes for the new bolt, and used a flat washer to spread the force across.  The lower bolt heads of the hidden mounting bracket offset the back of the ML-ACR  just enough to not be a problem overlaying the existing copper bus bars.  It is supported by the top two studs and the two bottom copper bus connections.  The other two holes on the ML-ACR bottom align with existing copper buses you don't want to mess with.

As the electrical studs do not match the Big Boy spacing I bent solid copper inter connecting bars as seen in the above photo.  As a source of easily bendable copper I used electrical conduit grounding strap (2, cut to size, drilled and bent appropriately):

 https://www.lowes.com/pd/Sigma-ProConnex-1-2-in-Rigid-IMC-Bronze-Grounding-Clamp-Conduit-Fittings/1000276669

The copper strap was convenient and easy to bend.  There are probably other solutions.

For installation, put the copper straps in place while you can maneuver the unit in place before you bolt the top mounting bolts.

Now for the switch.  I analyzed my desired usage and decided I really didn't care about status LED lights up front, so I didn't need the yellow wire.  Likewise I didn't care about multiple engine isolation so I only needed a ground source (easily found in the RRB) and could reuse the existing Battery Boost wire from the front.  The existing Carling switch is an illuminated single pole momentary on usually off switch that grounds the wire to the back of the coach.  That action would isolate the batteries rather than combine them. Easy solution.  I had an existing illuminated (On)-Off-(On) dual position momentary switch on hand.  That switch used to be my Gen Start/Stop switch but the bottom illumination bulb burnt out, however, I don't need that bulb in this case thus it got repurposed/recycled.  I popped the face plate off the Battery Boost switch ( use the removal tool found on eBay or Amazon so you don't break the switch faceplate tabs), wired the ground to the upper switch spade (remember that the very top two spades are for illumination, so the upper one just below the illumination one) thus the one which corresponds to pushing the bottom of the switch, put the existing wire to the back of the coach on the center spade, and tapped into the Step Cover 12+v source at that switch in the center of the dash wiring to the bottom switch spade. (Carling switches have up to 10 spade positions on the back side, the spades in the middle perform the switching functions with the optional extreme upper and lower sets are for illumination bulbs.) I thought that it was easier to run across behind the dash rather than running a wire down to front RB to a new spare fuse position on one of the boards. Since I would not be exercising the step cover at the same time as attempting to get a battery boost the step cover circuit seemed perfect to tap into for power.  On my coach, the step cover is fed a fused constant hot from the house battery bank.  Thus if my chassis was down I'd have (in theory) voltage from the house batteries to jump the chassis batteries to start the big Cat or generator.  So that switch gives me a normally open circuit so the ML-ACR automatically connects/disconnects on its own appropriately for various charging states.  If I need a boost, 12+ is supplied from the house to engage the ML-ACR.  And for peace of mind when I start the big Cat when plugged into shore power,  (and noting the starter draws a LOT of current), I can temporarily disconnect the banks by pressing the bottom of the toggle switch grounding the control wire to the back ... and I can crank without wondering if any "funny" stuff is happening to sensitive stuff on the house side.  As it's a momentary switch, it will go back to its automatic mode after a few seconds.  In looking at my factory wiring diagrams it seems the original Big Boy would engage even if the Magnum was charging the house at the same time as the alternator was charging the chassis.  So my conclusion was if I really had a reason to not connect the bank, I could just as easily turn the yellow knob in the RRB vs having the dash switch lock into the ground position. And being momentary I won't accidentally have it in a "wrong" position.  By reusing a Carling switch I had simply changing the face plate, my dash looks close to original.  Here's a picture of the adjacent switches pulled out so I can work on the "right" position with my fat hands in the cramped dash area:

Okay, now for the rear run box connection.  Control board 6 is tucked into the corner, but I was able to use a pin extractor and work out the 4th pin from the top on the edge connector.  This pin extractor compresses the locking pins so you can pull it out of the socket.  Shown for illustration purposes on a new pin:

And moving that wire from the dash into a new connector:

A while ago I installed two voltage displays on my dash so I could easily glance to monitor the battery banks.  My switch is dash illuminated consistent with the surrounding switches and matched the design of the faceplate.  A video of my ML-ACR in operation as I installed it:

Edited November 28, 2024 by amphi_sc