Pressure Transducers - what are they for?

[Steve P]

Steam gauge...  kidding of course

 

[Tom Cherry]

OK....lets keep this simple.  This post will deal with testing the Cruise Cancel Circuit.  Your cruise control does have (hidden in an obscure place in you manual) a reference to FAST IDLE.  Do the following.....but FIRST.  You have maybe a different relay.  I don't know about the socket...but if the socket is different from the standard BOSCH...then put this in AMAZON

301-1C-C-R1 U01 12VDC Automotive Relay 5 Pins SPDT

https://www.amazon.com/Pack-301-1C-C-R1-12VDC-Automotive-Relay/dp/B09YYXND24/ref=asc_df_B09YYXND24/?tag=hyprod-20&linkCode=df0&hvadid=607186602417&hvpos=&hvnetw=g&hvrand=16205463004535033950&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9060439&hvtargid=pla-1686318757426&th=1

The picture show the same type and maybe brand...so you can get spares there.....  OK...NOW TO THE TESTING....

ENGINE ON; Press Cruise ON or turn it ON; Press SET button or SET IT.  That should bump up the RPM some.  The point is that the Cruise is ENGAGED and SET. Next, apply the brake pedal as you would to DISENGAGE the Cruise.  That will then be how the Cruise is tested. Lets assume the Cruise will not engage.  

The next step will be redundant...but it will verify if there is a Relay Failure. Take some masking tape and label whichever Relays you pull or swap so that you know their ORIGINAL Number...Use RX & F or RX & R.

Ignition ON; Test the Turn Signals...go to the rear and verify; Either RIGHT or LEFT; Engine OFF; Turn off engine or Ignition.  Pull R6 (LR TURN) or R7 (RR TURN). Ignition ON. Verify or test the turn signal that has no relay.  ASSUME that the turn signal is NOT working. Ignition OFF. Replace Swap that Relay with the Front R2 BRK SIG RLY.  Ignition ON; Test whichever Turn Signal. If the Turn Signal WORKS....then R2F or the BRK SIG RLY is GOOD.  Engine OFF.  Install the RXR Turn Signal relay into the R2 Front Spot. Now....repeat the first test using the Fast Idle Cruise.  DOES IT WORK?  If NOT...then it is NOT a relay issue.  You MAY have done this... I can't remember...but now we know.

NEXT. Engine OFF; Swap the TWO diodes.  You can label one T and the other B so you know their original position.  Repeat the Cruise fast idle test.  IF all this did not fix the issue, then one last test before turning over to a tech who can trouble shoot....

Frank's analysis of the circuit is that the Treadle or Brake Pedal switch is ON.  NOW, if you really want to TEST that and some other things.  DO THIS.   Pull R2F BRK SIG RLY.  Stick a piece of wire or get a thin solderless terminal (spade type) from Lowes or such.  You can maybe use a needle. You need to be able to test on of the pin sockets in the relay.  Have your VOM on and verify a good ground lug up front. OK....FILE THIS AWAY.  You have the Intellitec BIRD (BiDirectional) module so you charge either way...as in when driving, both....or on shore...BOTH banks gets charged.  Look on page 178 of your manual.  There is a picture of it.  It has a GROUND.  You can use that for your meter lead during the test.

NOW...put your test "lead" or the wire that you will put into a Relay socket pin and put it on Terminal 85 (use the relay to verify which pin that is). Ignition ON.  You should have 12 VDC on terminal 85.  BUT, just for kicks....try it again on Pin 86.  OK...then the incoming power to the relay is GOOD. Have someone turn ON the ignition and check for voltage.  OK....no joy.  Then turn off ignition.  Do the next step

Next.  Pull the Diode next to the relay out. Use the TOP terminal.  Engine on. Repeat the Cruise fast idle test...but when the person steps on the brakes, have you meter set up for Continuity or OHMS and verify that there is a GROUND signal on the Diode.  IF NOT...then, it is a mystery to us as to WHY you DO have brake lights as you have tested.  So this is "redundant". 

You can ALSO repeat the test....Engine on Cruise fast idle....but run a test jumper from a ground and then insert into the BOTTOM terminal on the Diode connection.  That sends the GROUND and completes the relay coil circuit, since you know you have a good relay...That also assumes you replaced the Relay...but you are manually grounding the coil.

That's it.  Read this.  Let us know... 

OK...HOPEFULLY this will not get merged into the post above....but it might....(EDIT....it DID...so the following is for the WHEN DO YOU LOSE THE BRAKE LIGHTS...or what PSI...

Dennis pointed out the correct information on the brake light switch.  Here is what you do...

Engine on.  Fully air up.  Turn ignition OFF....then turn ignition back on....NOT RUNNING.  Have someone watch the brake lights.  You work the brake pedal and not the AIR Gauge (both or one...should NOT matter).  Tap or hold the brake pedal until the Brake Lights in the Tail Lights comes on.  Frank's theory is that the Center (Liddy) light is LED and there is a brief "NOW WHAT DO I DO" and that when it comes on and flashes...that is just a voltage issue....but the fact that immediately, if we understand you, all three come on....then that is normal.

So...be methodical. Press the brakes and get all three ON.  Let off.  Wait.... maybe 15 seconds.  Repeat.  You are trying to work your way down and drain the air tanks.  So, you watch the air gauge and note (mentally) the pressures.  The brake light should work all the way down to the first mark (presumably 20 PSI).  Now this IS an analog gauge...but if the CORRECT switches are in the system, you should have brake lights down to almost the bottom.  The correct switches should be 3 - 5 PSI.

NOW, if Monaco goofed....or the PO did some "replacements".....Who KNOWS.  He or a tech or even Monaco might have misdiagnosed the Cruise cancel and put in new switches.  BUT, they put in the WRONG switch and if the brake lights DO shut off when you "break" of pass 65 PSI, then they need to be replaced.  This SHOULD NOT impact your cruise issue...but folks do strange things...and Monaco was not infallible.  These switches will be on the firewall side and easy to spot on the brake treadle. The brake treadle has FOUR big lines.  Two IN an Two OUT.  On the OUT side, there will either be a T or a connection.  Let us know and we can get you a part number for the correct switch...

That's it....

[DennisZ]

BTW, I just went out to my MH to get it ready for a trip, the brake lights/ cruise disengaged with air pressure as low as about 15 to 20 psi. 

[Tom Cherry]

3 hours ago, DennisZ said:

BTW, I just went out to my MH to get it ready for a trip, the brake lights/ cruise disengaged with air pressure as low as about 15 to 20 psi. 

NO DOUBT.  I was a bit “lacking” about the treadle switches.  Frank enlightened me.  He said the spec on generic switches, the kind Monaco was supposed to use werer low….as in 3 - 4 psi.  That was my “spec”.  But anytime you probably drop below 20….or maybe 10….they get unhappy.

If Steve’s is 65, then ….wrong switch…

Thanks.  Our original comments were good.

[Steve P]

On 9/7/2023 at 8:22 AM, Tom Cherry said:

OK....lets keep this simple.  This post will deal with testing the Cruise Cancel Circuit.  Your cruise control does have (hidden in an obscure place in you manual) a reference to FAST IDLE.  Do the following.....but FIRST.  You have maybe a different relay.  I don't know about the socket...but if the socket is different from the standard BOSCH...then put this in AMAZON

301-1C-C-R1 U01 12VDC Automotive Relay 5 Pins SPDT

https://www.amazon.com/Pack-301-1C-C-R1-12VDC-Automotive-Relay/dp/B09YYXND24/ref=asc_df_B09YYXND24/?tag=hyprod-20&linkCode=df0&hvadid=607186602417&hvpos=&hvnetw=g&hvrand=16205463004535033950&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9060439&hvtargid=pla-1686318757426&th=1

The picture show the same type and maybe brand...so you can get spares there.....  OK...NOW TO THE TESTING....

ENGINE ON; Press Cruise ON or turn it ON; Press SET button or SET IT.  That should bump up the RPM some.  The point is that the Cruise is ENGAGED and SET. Next, apply the brake pedal as you would to DISENGAGE the Cruise.  That will then be how the Cruise is tested. Lets assume the Cruise will not engage.  

The next step will be redundant...but it will verify if there is a Relay Failure. Take some masking tape and label whichever Relays you pull or swap so that you know their ORIGINAL Number...Use RX & F or RX & R.

Ignition ON; Test the Turn Signals...go to the rear and verify; Either RIGHT or LEFT; Engine OFF; Turn off engine or Ignition.  Pull R6 (LR TURN) or R7 (RR TURN). Ignition ON. Verify or test the turn signal that has no relay.  ASSUME that the turn signal is NOT working. Ignition OFF. Replace Swap that Relay with the Front R2 BRK SIG RLY.  Ignition ON; Test whichever Turn Signal. If the Turn Signal WORKS....then R2F or the BRK SIG RLY is GOOD.  Engine OFF.  Install the RXR Turn Signal relay into the R2 Front Spot. Now....repeat the first test using the Fast Idle Cruise.  DOES IT WORK?  If NOT...then it is NOT a relay issue.  You MAY have done this... I can't remember...but now we know.

NEXT. Engine OFF; Swap the TWO diodes.  You can label one T and the other B so you know their original position.  Repeat the Cruise fast idle test.  IF all this did not fix the issue, then one last test before turning over to a tech who can trouble shoot....

Frank's analysis of the circuit is that the Treadle or Brake Pedal switch is ON.  NOW, if you really want to TEST that and some other things.  DO THIS.   Pull R2F BRK SIG RLY.  Stick a piece of wire or get a thin solderless terminal (spade type) from Lowes or such.  You can maybe use a needle. You need to be able to test on of the pin sockets in the relay.  Have your VOM on and verify a good ground lug up front. OK....FILE THIS AWAY.  You have the Intellitec BIRD (BiDirectional) module so you charge either way...as in when driving, both....or on shore...BOTH banks gets charged.  Look on page 178 of your manual.  There is a picture of it.  It has a GROUND.  You can use that for your meter lead during the test.

NOW...put your test "lead" or the wire that you will put into a Relay socket pin and put it on Terminal 85 (use the relay to verify which pin that is). Ignition ON.  You should have 12 VDC on terminal 85.  BUT, just for kicks....try it again on Pin 86.  OK...then the incoming power to the relay is GOOD. Have someone turn ON the ignition and check for voltage.  OK....no joy.  Then turn off ignition.  Do the next step

Next.  Pull the Diode next to the relay out. Use the TOP terminal.  Engine on. Repeat the Cruise fast idle test...but when the person steps on the brakes, have you meter set up for Continuity or OHMS and verify that there is a GROUND signal on the Diode.  IF NOT...then, it is a mystery to us as to WHY you DO have brake lights as you have tested.  So this is "redundant". 

You can ALSO repeat the test....Engine on Cruise fast idle....but run a test jumper from a ground and then insert into the BOTTOM terminal on the Diode connection.  That sends the GROUND and completes the relay coil circuit, since you know you have a good relay...That also assumes you replaced the Relay...but you are manually grounding the coil.

That's it.  Read this.  Let us know... 

OK...HOPEFULLY this will not get merged into the post above....but it might....(EDIT....it DID...so the following is for the WHEN DO YOU LOSE THE BRAKE LIGHTS...or what PSI...

Dennis pointed out the correct information on the brake light switch.  Here is what you do...

Engine on.  Fully air up.  Turn ignition OFF....then turn ignition back on....NOT RUNNING.  Have someone watch the brake lights.  You work the brake pedal and not the AIR Gauge (both or one...should NOT matter).  Tap or hold the brake pedal until the Brake Lights in the Tail Lights comes on.  Frank's theory is that the Center (Liddy) light is LED and there is a brief "NOW WHAT DO I DO" and that when it comes on and flashes...that is just a voltage issue....but the fact that immediately, if we understand you, all three come on....then that is normal.

So...be methodical. Press the brakes and get all three ON.  Let off.  Wait.... maybe 15 seconds.  Repeat.  You are trying to work your way down and drain the air tanks.  So, you watch the air gauge and note (mentally) the pressures.  The brake light should work all the way down to the first mark (presumably 20 PSI).  Now this IS an analog gauge...but if the CORRECT switches are in the system, you should have brake lights down to almost the bottom.  The correct switches should be 3 - 5 PSI.

NOW, if Monaco goofed....or the PO did some "replacements".....Who KNOWS.  He or a tech or even Monaco might have misdiagnosed the Cruise cancel and put in new switches.  BUT, they put in the WRONG switch and if the brake lights DO shut off when you "break" of pass 65 PSI, then they need to be replaced.  This SHOULD NOT impact your cruise issue...but folks do strange things...and Monaco was not infallible.  These switches will be on the firewall side and easy to spot on the brake treadle. The brake treadle has FOUR big lines.  Two IN an Two OUT.  On the OUT side, there will either be a T or a connection.  Let us know and we can get you a part number for the correct switch...

That's it....

OK, I did part of the diagnostics and when I got to the diode swap it seemed to clear up the cruise cancel problem.  In other words, the cruise cancel had been working intermittently while swapping relays and all the relays appeared to be good but when I swapped the diodes, the cruise cancel worked every time.   I will drive it cautiously for a few 100 miles in low or no traffic before I have confidence in it.

Now the question is what does the diode do that is labelled NEUT SNS CM ?  I'm picking up a replacement today at NAPA, but I'm still curious...

[Tom Cherry]

18 minutes ago, Steve P said:

OK, I did part of the diagnostics and when I got to the diode swap it seemed to clear up the cruise cancel problem.  In other words, the cruise cancel had been working intermittently while swapping relays and all the relays appeared to be good but when I swapped the diodes, the cruise cancel worked every time.   I will drive it cautiously for a few 100 miles in low or no traffic before I have confidence in it.

Now the question is what does the diode do that is labelled NEUT SNS CM ?  I'm picking up a replacement today at NAPA, but I'm still curious...

Ok…in a simple NUTSHELL.  The Diode is like a check valve on a water line.  It only allows the current to flow one way.  The circuit works like this.  There is positive coming into the BRK whatever relay from the ignition.  The OTHER side of the coil is the ground or negative side.  I think Monaco is afraid that there can be a “leaky” circuit.  The ECM sends out a 100% absolutely perfect ground signal.  That is what operates the relay…and cancels the cruise.  NOW the diode prevents current flow the wrong way.  So, they protect the ECM.  When there is currently…as the ground signal is made….technically the current is flowing from positive to negative.  YES…this gets complicated.  When there is NO GROUND signal…the diode prevents any leakage. BUT when the ECM sends out a GOOD TO GO…DISENGAGE Ground…you have current….then the diode says….DROP THE DRAWBRIDGE….let the positive coming from the coil (ignition activated) pass through and go back to the ECM.  

FWIW….this is NOT usually how a diode works.  We diodes on the positive lead on a taillight.  Two of them.  We then reconnect the towed vehicles light to one of them.  We conmect the brake light signal from the MH to the other.  The brake light signal then goes through the diode to the bulb….but the diode that is hooked up to the car’s sytem prevents feeding the voltage back UP the brake light circuits in the car.  This backfeed often destroys things in the towed vehicle or it blows fuses.

In this case, Monaco protects the ECM from getting a feedback…funky…. But it works.  If the diode is defective….it does NOT allow the gtound signal from the ECM to energize the relay.  Replace it.  Drive on…

The other diode is also an ECM protection.  Before the engine fires….the ECM says….ARE YOU (TRANNY) IN NEUTRAL.  There is a relay that says yes….and the relay closes and then the ECM says….start that sucker.  Put back the good diode.  Get a new or replacement…drive on.  I’d buy a spare….as well as a few relays….

[Steve P]

5 hours ago, Tom Cherry said:

Ok…in a simple NUTSHELL.  The Diode is like a check valve on a water line.  It only allows the current to flow one way.  The circuit works like this.  There is positive coming into the BRK whatever relay from the ignition.  The OTHER side of the coil is the ground or negative side.  I think Monaco is afraid that there can be a “leaky” circuit.  The ECM sends out a 100% absolutely perfect ground signal.  That is what operates the relay…and cancels the cruise.  NOW the diode prevents current flow the wrong way.  So, they protect the ECM.  When there is currently…as the ground signal is made….technically the current is flowing from positive to negative.  YES…this gets complicated.  When there is NO GROUND signal…the diode prevents any leakage. BUT when the ECM sends out a GOOD TO GO…DISENGAGE Ground…you have current….then the diode says….DROP THE DRAWBRIDGE….let the positive coming from the coil (ignition activated) pass through and go back to the ECM.  

FWIW….this is NOT usually how a diode works.  We diodes on the positive lead on a taillight.  Two of them.  We then reconnect the towed vehicles light to one of them.  We conmect the brake light signal from the MH to the other.  The brake light signal then goes through the diode to the bulb….but the diode that is hooked up to the car’s sytem prevents feeding the voltage back UP the brake light circuits in the car.  This backfeed often destroys things in the towed vehicle or it blows fuses.

In this case, Monaco protects the ECM from getting a feedback…funky…. But it works.  If the diode is defective….it does NOT allow the gtound signal from the ECM to energize the relay.  Replace it.  Drive on…

The other diode is also an ECM protection.  Before the engine fires….the ECM says….ARE YOU (TRANNY) IN NEUTRAL.  There is a relay that says yes….and the relay closes and then the ECM says….start that sucker.  Put back the good diode.  Get a new or replacement…drive on.  I’d buy a spare….as well as a few relays….

@Tom CherryYep, I grabbed two diodes at the local NAPA in Vernon NY near us.  I replaced the diode that seemed to be intermittent and unpredictable.  We are shoving off tomorrow for Vermont... 250 miles should be a good test drive for the cruise cancel!  And the new Neutral Sensor diode.

Thanks for the help.  I still plan to test the different legs of the R2 Relay (BRK SIG RELAY) in the front bay to see exactly how that behaves.  I also need to do the pressure check in the morning to see how low the pressure gets while the brake lights still work.

 

[Frank McElroy]

Steve, I'm curious to know if you are able to use your cruise control dash switches to put the engine in a fast idle more while parked and if now pressing on the brake pedal releases the fast idle mode.

[Steve P]

57 minutes ago, Frank McElroy said:

Steve, I'm curious to know if you are able to use your cruise control dash switches to put the engine in a fast idle more while parked and if now pressing on the brake pedal releases the fast idle mode.

@Frank McElroy Yes indeed.  Fast idle via the Set/Res double tap has been fine.  Using the brake pedal as the means to cancel what I was referring to, and doing, both before and after swapping relays front to back, and then swapping the diodes. The cruise cancel via the brake pedal was not reliable until I swapped the diodes.  Thank you for your assistance and the backstage discussions with Tom Cherry.  I'll report the test drive results Tuesday evening. 

[Steve P]

Well, it's been months... the braking cruise cancel and brake lights worked fine from NY to VT.  THEN I had a bicycle wreck and forgot to report success. All was well with both the brake lights and braking cruise cancel from Vermont back to home in Georgia and then from Georgia to Florida in October.  However, the Problems have recurred.

We packed up to leave the East Coast of Florida and go to the West Coast and we had no brake lights and no cruise cancel when braking.  We made the trip entirely with emergency flashers. 

My first step will be to swap diodes again in the left front run bay to see if the BRK circuit has been compromised again.  And if so, why would the diode fail again?  

I'll be calling a mobile diesel truck technician if all else fails.  Possibly even heading for Josam's in Orlando.

[Steve P]

Well, one of the diodes was bad again (D1).  So now the brake lights work.  But brake pedal cruise cancel still doesn't.  Also, now the ignition switch won't shut off the engine.  Pulling the BRK SIG RLY shuts off the engine. Any thoughts?

Replaced the BRK SIG RLY and engine will shut off.  But brake lights don't work.

HELP!

Edited January 22 by Steve P
Clarify

[Steve P]

7 hours ago, Steve P said:

Well, one of the diodes was bad again (D1).  So now the brake lights work.  But brake pedal cruise cancel still doesn't.  Also, now the ignition switch won't shut off the engine.  Pulling the BRK SIG RLY shuts off the engine. Any thoughts?

Replaced the BRK SIG RLY and engine will shut off.  But brake lights don't work.

HELP!

@Tom Cherry @Frank McElroy  I'm back to square 1 with no Brake Lights, and no Cruise Cancel (via the brake pedal -- cancel works via the console switch).  I had a mobile technician out today.  He got as far as discovering that R2 is not sending ground signal to R9 when the brakes are applied.  Instead, the leg is pulling about 4 volts (honestly, he may have said 0.4 volts).  I am sorry I have not further details until I speak with him again.  He is looking at the 2007 Ambassador wiring diagram I found in the Files section (supposedly for Knights as well).  And I discovered that even though my coach is 2008, it was built on a 2007 chassis.  I would appreciate any thoughts you might have as to how to isolate and cure the problem.

A NOTE of INTEREST: When I scrutinized the 2007 Ambassador wiring diagram(s), I found on page 22 that the layout of the front distribution fuse and relay box matches mine but the relay names of BRK or BRAKE relays shown inside the cover are different than those in the diagram.  Furthermore, the relay names on page 22 don't match those on page 1.  I added my suggested correlations to the names on my box cover in RED on the original diagrams (see page 1 and 22).  The revised set of diagrams is attached.  Let me know if you are able to confirm.  

The technician should be back Wednesday to continue diagnostics.  He was pretty perplexed.  All the relays in the front distribution box tested good, as did the diodes and all the fuses.  He's taking a hard look at the wiring diagrams before continuing.

Thanks in advance - Steve P

2007 Ambassador (chngs in red p1 and p22).pdf

Edited January 23 by Steve P

[Steve P]

The BRK SIG RLY is only showing 4.4v on pin 30... does this indicate a high resistance in the circuit prior to that... say from the service brake or wiring from it?  With that voltage low, how would it affect the downstream relays?

[Tom Cherry]

40 minutes ago, Steve P said:

The BRK SIG RLY is only showing 4.4v on pin 30... does this indicate a high resistance in the circuit prior to that... say from the service brake or wiring from it?  With that voltage low, how would it affect the downstream relays?

You need to blow up or chase the print that shows the “entire circuit”.  If the relay you are looking at goes or comes from the ECM, then that may be correct.  If you trace it to a real or “genuine” 12 VDC Chassis source, then, MAYBE HIGH RESISTANCE….

BUT…. A ECM Circuit may well be within range.  Monaco was somewhat, at least to me, inconsistent.  So….is T 30 The “incoming” signal and 87 the outgoing…..???

Don’t forget that Monaco often switched “GROUNDS” on the 30/87 Contacts.

Figure it out….it may well be a “Hello, I’m a FRIENDLY RETURN signal …. YES….all is well…..you can complete the ( Fill in BLANK) circuit”. Therefore troubleshooting, as some have or may have suggested or whatever…..by putting “12 VDC” on that thar contact…..might not be wise.

The Brake Light circuit is a horse of a different color and maybe sex.  Understand both ends.  T30 & T87.  Know which is incoming.  Know that type of signal…. 12 VDC or GROUND or lower 5VDC or so ECM Component….

[Steve P]

Trying to chase the whole circuit led the technician (and me with not a clear understanding) to a bad TRLR BRK RLY in the front distribution panel.  We didn't have a spare (it's the notorious G8VL-1A4T-R-L, which I just found and ordered on eBay).  Meanwhile, oddly enough, pulling that relay restored my brake lights (on the coach and on the toad), and restored the operation of the cruise control cancellation by the brake pedal.  So now everything works, except maybe the brake controller circuit (I'm unclear whether this circuit controls the Brake Buddy or whether that's controlled by the trailer "lights" circuit directly, so I'll be figuring that out next).  

Note:  the Omron G8VL-1A4T-R-L is unmarked in any way so I can't tell without some tinkering what the pins are (30, 85, 86, 87).  I might suspect that the copper ones diagonally across from one another are 30 and 87 (for carrying higher current) and the other two that look zinc would be 85 and 86.  Describing the relay as "bad" doesn't tell me what it's behavior is (open, closed, under what condition).  I'm completely mystified as to why this particular relay knocked out the brake signal(s) that controlled my pedal cruise cancel and my pedal brake lights.  But it did/does.

I'm no expert in chasing the prints for clues, but I'm trying...  by the way, as far as I can recall, the TRLR BRK RLY has never been replaced, nor swapped.  I guess an intermittent connection to this relay could have eventually killed it, or high resistance on the trailer plug/receiver (the connector on the toad had two bad pins (by that, I mean that each pin is a circular post, but the post was split into 4 separate prongs.  Think of the top view where the circular post is divided by a + cutting it into 4 sections/prongs.  It's a crude way of making the 4 prongs exert pressure on the sleeve when it's pushed over them.  Gosh what an awful explanation.  I'll try to find a pic.  Anyway, on two of the 6 posts, one of the four prongs was broken off from wear and tear.  With only three prongs per post on those two, perhaps the resistance increased, and with it, heat...  not a good thing obviously.  It's a bit troubling that the fuse protecting the relay didn't blow.  

Until I can get a replacement, the TRLR BRK RLY is removed, and the brake pedal produces brake lights and cancels cruise.  I still feel like "this ain't over", but at least I can get home soon.  I'll let you know when the replacement relays come in if I'm still 100%.

Thanks to everyone who has offered advice and assistance.  

Best regards,

Steve P

[Tom Cherry]

14 minutes ago, Steve P said:

Trying to chase the whole circuit led the technician (and me with not a clear understanding) to a bad TRLR BRK RLY in the front distribution panel.  We didn't have a spare (it's the notorious G8VL-1A4T-R-L, which I just found and ordered on eBay).  Meanwhile, oddly enough, pulling that relay restored my brake lights (on the coach and on the toad), and restored the operation of the cruise control cancellation by the brake pedal.  So now everything works, except maybe the brake controller circuit (I'm unclear whether this circuit controls the Brake Buddy or whether that's controlled by the trailer "lights" circuit directly, so I'll be figuring that out next).  

Note:  the Omron G8VL-1A4T-R-L is unmarked in any way so I can't tell without some tinkering what the pins are (30, 85, 86, 87).  I might suspect that the copper ones diagonally across from one another are 30 and 87 (for carrying higher current) and the other two that look zinc would be 85 and 86.  Describing the relay as "bad" doesn't tell me what it's behavior is (open, closed, under what condition).  I'm completely mystified as to why this particular relay knocked out the brake signal(s) that controlled my pedal cruise cancel and my pedal brake lights.  But it did/does.

I'm no expert in chasing the prints for clues, but I'm trying...  by the way, as far as I can recall, the TRLR BRK RLY has never been replaced, nor swapped.  I guess an intermittent connection to this relay could have eventually killed it, or high resistance on the trailer plug/receiver (the connector on the toad had two bad pins (by that, I mean that each pin is a circular post, but the post was split into 4 separate prongs.  Think of the top view where the circular post is divided by a + cutting it into 4 sections/prongs.  It's a crude way of making the 4 prongs exert pressure on the sleeve when it's pushed over them.  Gosh what an awful explanation.  I'll try to find a pic.  Anyway, on two of the 6 posts, one of the four prongs was broken off from wear and tear.  With only three prongs per post on those two, perhaps the resistance increased, and with it, heat...  not a good thing obviously.  It's a bit troubling that the fuse protecting the relay didn't blow.  

Until I can get a replacement, the TRLR BRK RLY is removed, and the brake pedal produces brake lights and cancels cruise.  I still feel like "this ain't over", but at least I can get home soon.  I'll let you know when the replacement relays come in if I'm still 100%.

Thanks to everyone who has offered advice and assistance.  

Best regards,

Steve P

Fascinating….  OK…. First GOOGLE Omicron Relay PN Diagram,  that shows the pins.  The pins are also, I thought, stamped on the side.  

As you said, it takes some time to follow the circuits….printed out and blown up and highlighters or colored Sharpies work.  Still the SAME WARNING.  Any circuit involving the brakes and “gee….this ‘ill fix it” should be only done with full understanding.

Next up.  The infamous Trailer Brake relay.  Monaco added that STANDARD feature in 2005.  Messed it up.  A Brake Control company, US Gear, caught it and has a “FIX” in their archives and it has been posted many times.  Monaco then fixed it in 2006….but as usual….there were exceptions.  YOUR 2008 should be OK.

The Trailer Brake Relay, and Monaco also changed names or modified it, was to CONVERT the GROUNDED Brake Light Circuit to a 12 VDC signal.  Don’t ask why Monaco was “backwards” from a car. The ON SIGNAL for the MH brake lights was a NEGATIVE SWITCHED signal.  

NOW….  Don’t knwo or understand the reference to “Brake Buddy”.  There is a 5 wire harness….some say, DEVILISHLY and with malice of forethought…..CAREFULLY HIDDEN on the lower left area of the dash….either up under or behind or in corner of the driver’s console.  A topic and task that has been maligned and discussed here….way too often.

That bundle has 5 pins on a 6 pin connector.  12 VDC ALL TIME (CHASSIS); 12 VDC IGNITION ON; 12 VDC BRAKE LIGHT ON (from the relay); WIRE TO REAR….Tyoically the 4:30 PIN in the 7 pin harness…..your manual shows it.  And GROUND.

It is used with a REAL 12 VDC Electric Braking “Trailer”.  The control is wired, per the install instructions, and the “blank” or wire to the rear 7 pin is attached to the SIGNAL TO BRAKE SYSTEM wire.  

UNLESS you have a hard wired “Toad Braking” system that “WORKS LIKE” a trailer brake system, it is rarely used.  I THINK US Gear discontinued the Universal Tow Brake system.  I had one and it was great….but don’t recall anyone saying there was a replacement or other vendor.

NOW….I ASSUME that you drove the MH with someone behind you and your were in cell communication.  Tested the exhaust brake?  I do NOT know if it is functional.  If the Brake Signal Relay is removed….you MIGHT not have an EXHAUST brake…..but I don”t profess to understand the circuit and haven’t printed and lined yours out.

There is a LOT of interaction between the Brake Signal relays and the ECM.  Of that I am certain….and the “cancel” signal on some are diode protected and a nightmare.  Just be sure the tech has all the prints and can trace and understand or call a buddy….  This is important.

The rear “CYCLOPS” or the Liddy (as in Elizaberh Dole) light comes from the Exhaust brake, I think, but it also works when you depress the service brake light.  You have to drive, press the brake, then use the exhaust only and then both and have someone check the lights to see if all is well.

Relays be strange critters.  Tapping one is usually the first step.  Swapping with a known good one is next.  Relays can be “BAD” then repent and be “GOOD”.  Some fall off the wagon….others are fine.  Just reinserting a relay and getting a good or better connection can work.

ASK ANY EXPERIENCED TECH.

I HOPE someone who has time will draw or sort this out….but your 4.4 VDC is telling and is typically an ECM only signal….

Let us know,,…

 

[Steve P]

No diagram and no pin numbers are stamped on the relay.

I'm still hooked up at an RV Park. Only stationary testing was performed.  Wheels chocked, service brake off, jacks up ignition on, and off.  So, the exhaust brake is untested, as are any other functions.

The Brake Buddy is a removable, portable brake assist device that sits in the floorboard and applies proportionate braking.  I need to re-read the manual, but I think it does so based on the trailer brake signal between the RV and the toad.  That signal is working correctly, since the toad has rear brake lights when the RV brake pedal is depressed.

[cbr046]

If I remember right the brake signal enables the Brake Buddy to brake but uses an accelerometer to drive the proportional braking and push on the toad's brake pedal. 

You should be able to swap with other relays.  If the relay looks the same it's probably ok to swap.  "Your mileage may vary".  I considered the Horn relay the one I could do without (for a short time). 

- bob

[Steve P]

1 minute ago, cbr046 said:

If I remember right the brake signal enables the Brake Buddy to brake but uses an accelerometer to drive the proportional braking and push on the toad's brake pedal. 

You should be able to swap with other relays.  If the relay looks the same it's probably ok to swap.  "Your mileage may vary".  I considered the Horn relay the one I could do without (for a short time). 

- bob

I believe you are correct re: the Brake Buddy. 

I will do the swap for something inconsequential if the exhaust brake doesn't work.   Good idea!

[Tom Cherry]

5 minutes ago, Steve P said:

No diagram and no pin numbers are stamped on the relay.

I'm still hooked up at an RV Park. Only stationary testing was performed.  Wheels chocked, service brake off, jacks up ignition on, and off.  So, the exhaust brake is untested, as are any other functions.

The Brake Buddy is a removable, portable brake assist device that sits in the floorboard and applies proportionate braking.  I need to re-read the manual, but I think it does so based on the trailer brake signal between the RV and the toad.  That signal is working correctly, since the toad has rear brake lights when the RV brake pedal is depressed.

Odds are, that the ONLY connection between the Brake Buddy and the Toad is a 12 VDC power plug…

Brake Buddy typically, but you NEVER know, uses an inertia pendulum.  Think of it as “decelometer”.  When you apply brakes, or even drastically gear down, then the “sensing” device engages and applies the vehicle’s brakes.  That was how mine worked.  There was, and is, I think, one that has a wireless remote. It blips a light when the unit “applies” the brakes.  It also works the other way, so if you need extra braking, you can “dial it up”.

The lights on your towed vehicle can be wired or configured two ways.  One….the simple, but dangerous as to your car’s electronics, is in parallel.  So….when the MH’s Brake/Turn signal comes through, then the filament lights up.  OPPS, sends a voltage or back-feeds into the car’s circuits.  Some vehicles use MPX and/or sensing electronics and they don”t digest stray voltages well.   Really get upset.

The preferred method is diodes.  That isolates the filaments….so you have a diode that has two incoming and one outgoing signal. The diodes prevent the signal from the MH to go to the car and vice versa.  Some folks that have vehicles with “will come on anytime pedal is pressed” have to put in a special harness or isolate.

That’s my take.  If you have a multi Pin connector on the Brake Buddy, read it.  Never say never, but the number ONE selling feature of a BB is “no modification to car’s wiring”….completely self contained.

 

[cbr046]

4 hours ago, Tom Cherry said:

That’s my take.  If you have a multi Pin connector on the Brake Buddy, read it.  Never say never, but the number ONE selling feature of a BB is “no modification to car’s wiring”….completely self contained.

Edit:  I'm quoting Brake Buddy when I have an Even Brake system.

I needed a brake signal when testing my Brake Buddy.  Otherwise it wouldn't activate. 

- b

Edited January 26 by cbr046

[Tom Cherry]

17 minutes ago, cbr046 said:

I needed a brake signal when testing my Brake Buddy.  Otherwise it wouldn't activate. 

- b

Was it “wired into” the car’s harness?  Mine was nothing but a plug for power to keep the compressor running. This is the way that mine worked and was often discussed here….

https://www.brakebuddy.com/assets/bbclassic.pdf

OK….still confused,  BUT, I DID watch the video for the Stealth.  It APPEARS to be a “CLONE” of the US GEAR Universal Tow Brake.  There is an “up front controller and the video glosses over the installation.  BUT the manual shows the wiring diagram.  It HAS to have the Monaco Standard “trailer” brake control harness…which you cut and splice.  That is the ONLY place that you “cut into a system”.  The Brake signal wire, from the harness goes to it.  Main power and Ground and THEN the infamous BLUE WIRE to the back.

https://www.brakebuddy.com/assets/stealthinstructionmanual.pdf

You do NOT cut or find the TOWED Vehicle’s “BRAKE PEDAL” or stop light switch.  The signal from the MH’s Brake light is fed into the dual controller which then drives the box in the Toad vehicle.  Same “flex cable” actuation as the US GEAR. As I said….clone or “reverse” engineered.  I DO wonder when this came out inrelation to when US Gear discontinued the UTB system.

Could you elaborate on where or how in the towed vehicle you had to have that??  Maybe a different unit.  But now, unless I missed something….the hard wired “STEALTH” or the “no wiring required” portable Brake Buddy.

Thanks….

 

[Steve P]

My Brake Buddy (BB) is the Vantage Select 39504.  It is powered by a 12v cigarette lighter socket wired on separate 15A circuit.  That's the only power to the unit other than the signal from the breakaway cable.  No brake signal from the RV...  the BB uses inertial style braking.

The reason for the confusion is that I also have a Hopkins cable from the 7-pin socket on the RV to a 6-pin socket on the toad.  As best I know, it's functions are: turn signals, tail lights, brake lights, and flashers.  What I don't know is what electrically happens to combine the two brake light signals (one when the BB presses the brake pedal, and one via the cable connecting the RV to the toad).  There could be diodes in the mix... don't know.

No brake controllers of any kind as far as I know... 

[cbr046]

3 hours ago, Tom Cherry said:

Was it “wired into” the car’s harness?  Mine was nothing but a plug for power to keep the compressor running. This is the way that mine worked and was often discussed here….

MY BAD!!!  My system is Even Brake, not Brake Buddy.  Looking at the 2 instruction sets Brake Buddy is much simpler!  The Even Brake needs to see toad vehicle brake lights as confirmation the toad brake pedal is pressed by the unit.  My "installation" was static - no base plate but I had to verify the Even Brake would work (purchased used). 

https://www.roadmasterinc.com/pdf/85-4593.pdf

But I knew I had to locate a brake signal . . .

- bob