Rear electrical circuit board fire - 2012 Knight

[Ed-Dans]

I have a 2012 Monaco Knight 40PDQ.  This is my first motor coach and I am way over my head.  Any help will be appreciated.  I had a fire in the rear electrical circuit board located in the box above the chassis batteries.  The box contains the battery cutoff switches and battery relay.  

My questions are:  

1)  What is the purpose of this circuit board? ( I did find a replacement on line. )

2) Any ideas on what may have caused the fire?  The coach was not being used and I had it plugged up to 20 amp extensive cord to try and maintain the batteries.

3) There is an acrylic panel that the circuit board attaches to which also melted.  I assume it is some type of insulator.  It needs to be replaced.  

     Any ideas on where I could find one?

Again, any help is greatly appreciated. A circuit board image is attached. 

 

IMG_6630.HEIC

[Happycarz]

My 2008 Camelot used the same board. The gray connector in lower left powers ignition switch. The ignition start circuit come back to same 4-pin connector and then to the starter solenoid. That is just part of this board. Look at the schematic for more info.

Hopefully, yours is wired the same as the 2008-2009 Camelot’s. Dunno.

I can’t help on why it happened.  Maybe you can post some pictures.

 

A better schematic.

[Ed-Dans]

Thanks, that helps.  I appreciate it.

[MyronTruex]

Need more information on the fire. Was this board burned by the fire or did it burn up by itself?

Loose connections can cause a lot of heat build up but a chafing wire is more likely the culprit. 

That circuit board is impressive. Looks like it does a lot of things. I don't want to speculate on all of its functions just yet. 

Please post a few more pictures of the compartment area.

 

[Ed-Dans]

The fire originated on this board.  I believe it connects to the alternator, front electrical panel, house fuse panel, and battery isolator relay.

I have attached more photos of the burnt circuit board, burnt acrylic board, electrical panel box, and manuel.  Thanks for the help.

IMG_6634.HEIC IMG_6635.HEIC IMG_6636.HEIC IMG_6637.HEIC IMG_6638.HEIC IMG_6639.HEIC IMG_6640.HEIC

[Ed-Dans]

Here is the burnt acrylic panel that the circuit board attaches to.  Does anyone know where I can find one?

IMG_6641.HEIC IMG_6642.HEIC

[MyronTruex]

Looks like plenty of opportunity for a physical short from the house power to the ground lug on the circuit board. There may have been enough power flowing to burn the traces and melt things as shown without blowing a fuse that appears to be just above. 

A loose connection would not likely cause the heat build up since things were basically at idle. That is, no heavy battery charging etc.

Unfortunately I do not have the resources at hand to recommend a piece of acrylic or whatever that piece was. Acrylic is easy enough to source by itself and maybe you just need to find a small panel and cut your own. 

I do not think you have anything outside of that area to be concerned with other than to go over every wire connection you can find in and about the battery compartment. Keep us posted as you progress and the fire extinguisher handy as you rebuild the area. 

 

Forgot, you asked what it is used for.

It appears it is a distribution system for some simple circuits while providing fuse protections.

It also looks like it is part of the startup of the big engine. A signal that the transmission is in neutral through one of the relays and then the larger one with the big wires supplies a voltage to another relay to the starter. This would not handle the current of a starter by itself so it then controls the actual starter relay on or near the starter,.

There is an ignition input that would be important to control when some of the circuitry becomes active. 

The large solenoid inside the compartment is used for the emergency combining of the batteries when needed controlled by a switch near the driver. The solenoid also combines the batteries for charging. I see you have a small black box nearby that shows a control board for bi-directional charging. 

You may find that large solenoid becomes very hot when plugged into shoreline for long periods. That is fine. 

In any case, be sure to check both battery bank voltages when connected to shoreline but be sure to measure after a couple of minutes after connection. There is a delay involved. Both banks should be virtually the same voltage. 

[Ed-Dans]

Thank you for the great information.  My plan is to repair it myself and then have a qualified technician/electrician troubleshoot the issue.  One quick question, what would cause a physical short from the house power to the ground lug?   (i.e. bad house batteries) Again, I am a novice so any information is helpful.  

[Happycarz]

Ed, your pictures were certainly a help. I hope you can follow along with the pictures below.

Everything in the gray box is 12 volts, from both the chassis batteries and house batteries. No 110v in there.

Looking at the damaged area, it looks like the house battery stud might have rubbed through the black ground cable. While taking pictures of mine, I find my black cable lodged tightly against the battery stud. (Ben and Tom, are you paying attention?) The part I don’t understand is why didn’t the 125a fuse blow. Did you happen to find any loose tools in that charred mess?  With the black wire, and stud, being the only ground there, I just wonder if a metallic foreign object could have caused this.  One would think the 125a fuse would have protected such damage. 
With others looking at these pictures, maybe they can add to what might have happened.

Hopefully the pictures load in order. I’ll put your picture first, then a picture of my rear run panel. Then there will be closeups of the left and right boards. And a better picture of the wiring schematic for the board. I believe the black wires on the schematic dropping down from the chassis and house studs are actually traces on the back of the PCB. They terminate at the connectors for solar.
The three white wires on the upper left of the board will have writing on them to match the schematic. Theses wires go out through the back of the box in that corner.

I’m sure you will have questions, so ask away.

 

[Ed-Dans]

Harry, thanks for the great information and photos.  No, I did not find any foreign objects.  The coach was not being used.  The chassis batteries had gone bad and were replaced.  The water level was low in the house batteries, 4 deep cycle 6v, and I added distilled water.  The coach was plugged in to 20 amp service with a long extension cord in an effort to keep the batteries charged.  I wondering if I did something wrong or if I need to look for a short somewhere in the coach.  

[Tom Cherry]

All I can add is the following…

FIRST….if you use a 20 Amp extension cord….make use it is rated for 20 amps.  Make sure it is plugged into a REAL 20 amp receptacle (T Slot on one prong).  Make sure the breaker for it is 20 amps.  Make sure it is NOT a GCFI or is downstream of a GFCI Breaker.

SECOND….set the inverter (probably Magnum) to SHORE 20….if you find the outlet above is only 15…then set it there.  Unplug or use a power strip and turn off all  TV and electronics….standby drains a small parasitic load,  unplug the Microwave.  Do not leave a refrigerator running.  Unplug even phone chargers…

THIRD....as to the FIRE...  Harry has posted info as well as Paul.  I will add the following....  MAKE SURE THE BOARD is the same.

Here is the ORIGINAL Monaco Rear Run Decal Print... 16623002 there is NO Revision NUMBER.  

https://revrvparts.com/item-detail?itemId=46572&organizationId=9

$1443 YEOUCH from REV.  I would contact REV with my VIN number and also verify that board will fit or is the SAMe REVISION number.  REV SHOULD have a Where USED internal list on this part.  

ONCE you verify what the exact PN is, you MAY, as Harry posted....LUCK OUT...if he is correct, then here are two sources...

https://www.ebay.com/itm/133146116291?nma=true&si=WAE%2FbIazU6q%2F1dtflQVPOQuhlIA%3D&orig_cvip=true&nordt=true&rt=nc&_trksid=p2047675.l2557

This Ebay is closed due to the seller being out of town.  BUT he had several.  Look at it and it is a Mega Tech from Oregon.  You can, I think, contact them....or that is what I read.  $99 compared to $1453...

ALL - COMMENT.

I am NOT fanatical as some, but I DO DO a PM on the front and rear boards and tighten every screw and nut.  I THINK I am on the third one on the rear.  YES, my pictures look like that... and YES....the board looks the same....

I have found loose connections.  There has to be a DEAD Short between the board and the source....  YES, the GROUND looks suspicious.....but I also wonder about the fuse holder above it.  That one has, on mine, a MEGA FUSE...200 Amps.  The Buss can be salvaged.  Tell your TECH not to use anything with the BUSSMAN IGNITION RATED ANL fuses.  The cheaper ANL don't last.  I have SPARES of all my ANL's and ALL are the OEM Bussmann design and IGNITION rated.  These can be bought on Amazon or from online electrical site.

Wish I had MORE>>>>but contacting Rev and seeing if their board is what you NEED and getting the Particulars (the Mega Tech ## as well as the REV level....)

Rear Distribution Box.pdf Rear Electrical DECAL ISL.pdf

[Gary Cole]

Thanks for the pictures Harry and for pointing out the contact problem with your ground wire. I also noticed from your pictures, and from  experience with my own coach, that Monaco did not consistently (rarely) use a necessary washer between lugs and nuts. A washer is necessary in order to assure that friction between the nut and lug does not distort torque values and, also very important, provide an adequate clamping area in order to assure low resistance. A belleville or cone washer with an approved conductive coating used with a grade rated lock washer between the nut and clamping washer is the industry standard. 

Just an observation. The installers who install the wiring for these coaches are not required to have a license or experience of any kind.  They might have been hanging drywall or running sprinkler pipe the week before they went to work for Monaco. 

Edited February 28, 2023 by Gary Cole

[Ed-Dans]

Tom, thanks for the comments.  Everything was off but not unplugged.   I believe everything was rated at 20 amps but I'll recheck.  It was at least 100 feet of extension cord and it was on a GFCI outlet.  How does the GFCI affect it?

 

[Tom Cherry]

8 minutes ago, Gary Cole said:

Thanks for the pictures Harry and for pointing out the contact problem with your ground wire. I also noticed from your pictures, and from  experience with my own coach, that Monaco did not consistently (rarely) use a necessary washer between lugs and nuts. A washer is necessary in order to assure that friction between the nut and lug does not distort torque values and, also very important, provide an adequate clamping area in order to assure low resistance. A belleville or cone washer with an approved conductive coating used with a grade rated lock washer between the nut and clamping washer is the industry standard. 

Just an observation. The people who wire these coaches are not required to have a license or experience of any kind.  They might have been hanging drywall the week before they went to work for Monaco.

Spring washers are split ring circular washers.These are not preferred in electrical applications as in case they break in service,there are chances of them flying off and going to electrically live areas.Their use is limited to lock the nut rotation.

In current carrying joints (say 500A or more) belleville spring washers(disc washers) are used to provide continuous pressure on contact areas to take care of the unequal expansion of current carrying parts and fasteners.The order of the bolting  system is bolt head/belliville washer/ plain washer/ current carrying joint (two parts)/ plain washer/belleville/nut/projecting length of bolt.Plain washers are special ones having more OD to transmit the pressure from Belleville.These disc washers can be fitted in series(then their clamping load adds up) or in parallel(deflection adds up with same load)

Current carrying at a joint depends on the surface area(or A /mm2 normally 0.5 A/mm2 in oil and less value for air,surface finish and contact pressure.
The above was a quote about electrical connections and washers and such.

I was the chief engineer for a large fastener company and we followed the Industrial Fastener Institute’s “Bible” or the IFI.  In the 70’s, spring or split washers was THE standard.  As electronics and torque and vibration simulator and a lot of Statistical Process (Quality) Control techniques were used, the industry changed.  I had a discussion with a major bolt and nut manufacturer a few years ago and questioned the fact that Blue Ox and Roadmaster were using split washers and the torque and grades did not meet the IFI standards.  I then discussed this with a design engineer, who supposedly actually went back to their fastener supplier and LO & BEHOLD….they recommended using flat washers for contact as well as torque retention,  but, that would have involved reworking the instructions and such.  

So, they said….you are correct, but Loctite Red will work better….we left it there.

I know from a LOT of tinkering that there are many types of “electrical” locking “systems” on our motor home. The once an EE and background in automotive and common sense says many of our systems are carryover before the IFI started getting more sophisticated.

we now have locking nuts on 20Amp fuses, and some of of my ANL fuses did not have the required flat washer to give proper clamping as well as contact.  Some big studs have small nuts and you only get half or less of the contact under the stud or clamping,

I DO NOT LIKE SPLIT WASHERS…..for electrical, but keep check.  A properly torqued nut with a cone or Belleville washer is great.  But in lieu of that as many folks like Lippert just put on a nut and a split washer, I am of the school that says, a washer of the diameter of the contact portion of stud is needed….and then use a nut and torque it.  Otherwise, find the proper one, but in lieu of that, a nyloc nut…but bear in mind it is supposed to be used once….otherwise, properly torque and do PM on a flat washer. 

In all fairness to Monaco, when they were stable, the crews were stable.  When they ramped up, you had folks to cross train the Sheetrock techs….and they paid well.  There was very LITTLE written “Operator Instruction Sheets”.  Having spent 10 year in a Ford Q-1 certified assembly plant as the Manager of Manufacturing Services, my teams wrote more paper than a check bouncer….and we had controls.  Monaco never had that, but they had trained people.  The decline happened when they cut back.  They then went bankrupt and the issues with quality and consistency increased an order of magnitude.  I was friends with a HR General Manager…large dealership and knew his techs…..Navastar never came close to the original Monaco….  REV?  Don’t know….

12 minutes ago, Ed-Dans said:

Tom, thanks for the comments.  Everything was off but not unplugged.   I believe everything was rated at 20 amps but I'll recheck.  It was at least 100 feet of extension cord and it was on a GFCI outlet.  How does the GFCI affect it?

 

Simple….Talk to Magnum.  They will tell you up front that their inverters will trip MOST GFCI.  The drill is to keep lowering the Shore amps.  Even as low as 5 amps may not work.  They also advise to find a NON GFCI outlet.  Their instructions for their OWN GFCI “outlet” kit is to also turn off Search Watts….that has an impact.

The issue is that if you downrate the circuit, you have LESS power to the inverter.  If you ever do the math….you might get 100A DC….and that would be at Bulk and the voltage is in the high 14’s.  Say 15.  That is 1500 watts….divide by 120 and you get say 13.  But , if you have left on items and standby and then also have to power the Inverter’ PCB and fans…..bingo….you run out of current.  Even a regular 20 Amp 120 VAC circuit could experience a voltage drop.  

That’s the overview.  OBTW….you need (may) to lower the charge rate.  That is what actually is applied (on a percentage rate) to the charger.  Thus. If you want to run a Res refer in storage or boondocking in someone’s driveway….then you need to knock down the charging rate….as you will trip the breaker…..and don’t even THINK about using a GCFI.

Call Magnum and talk to them….

[Ed-Dans]

Thanks Tom.