Wet bay heater electric Cargo Heater (System Heat) inoprative

[cbr046]

That snap-disc is a PITA to get to.  Mine's mounted (not dangling) on an aluminum support up high in the back of the bay.  I have to lay on my belly and crawl half way into the wet bay to get to it.  To unmount it (I think it's riveted) and stick it in some ice while half way into the bay wasn't on my agenda. 

Even easier (IMO)

1.)  Unplug the heater

2.)  Remove the two knobs on the sides of the heater.  Remove the heater.

3.)  There's 4 phillips screws holding the front panel on.  Remove the screws.  Remove the front panel.

4.)  Without power to the heater connect a set of "VOM" (Sorry Tom, but I laugh every time you use that ancient expression!) leads across the thermal fuse.  Set the DVM to Ohms on a low scale like 0 - 2k.  You should see near zero ohms. 

This is the problem 99% of the time, and it took all of 5 minutes to check. 

*IF* that's the problem you'll need to use the instructions Frank McElroy and Tom Cherry developed to replace the fuse.  See the "Cargo Heater Repair" insert in Tom's post above.

Let us know what you find.

- bob

 

 

[Hubert wells]

I have a 2008 Monaco Diplomat, can’t get my wet bay heater to work .

I installed a new heater nut still will not come on. The system heat light doesn’t work either , I’ve tried when the temps are below 40 degrees.

I have tried several times to locate the snap disc , but unable, even had it at Lazy days in Knoxville and they couldn’t locate it , they said some did not have them installed, could this be correct ?

thanks for any input .

[jacwjames]

24 minutes ago, Hubert wells said:

I have a 2008 Monaco Diplomat, can’t get my wet bay heater to work .

I installed a new heater nut still will not come on. The system heat light doesn’t work either , I’ve tried when the temps are below 40 degrees.

I have tried several times to locate the snap disc , but unable, even had it at Lazy days in Knoxville and they couldn’t locate it , they said some did not have them installed, could this be correct ?

thanks for any input .

Only way that a snap disc would not be installed is for the heater to have a thermostatic type control.   If you don't have a knob on the front to adjust then that's not a possibility.

One option would be to install a new snap disc in a better location, just have to check the wiring. 

On my coach I have two circuit breakers in my passenger side rear electrical bay.  One is for the heater itself, I think it is 30 amp, and the other is for the system heat switch which is 5 amp.  If yours is similar you might check to make sure the power is passing.  One time when I could get my system heat to work I found one of the nuts loosened up, tightened it up and all was good. 

[MyronTruex]

The snap disc is probably behind the wet bay panel on the right side. A real pain to get to of course. Looking at my pictures it shows it on the left side but I suspect I just moved it over there for some reason. In any case, it is/was behind the panel. 

I have done so many modifications over the years such as turning my water hose reel around so the hose comes off the top versus the bottom. Now it drops right down through the hole. Works like a charm now.

Removed my macerator and stored it in the compartment on the opposite side of the wet bay. That is another modification allowing access to that end.

Cut a larger hole in the bottom and installed a new deck plate so the sewer outlet actually can be turned down and goes straight through the misaligned hole from the factory.

Turned the upside-down faucet over. 

Made my own wet bay plate that can be disconnected with four easy bolts. Having to replace a check valve or making other modifications is much easier with that access. There is now storage space above the wet bay panel. 

I know it does not look as elegant as the factory plastic did but it sure is a lot more functional.

I will dig up some pictures to help you find the snap disc

Edited November 25, 2022 by myrontruex
addin pictures

[Dbircky]

I found my snap disc on the floor under the water pump on the opposite side from where the heater was.  The heater was also installed behind the panel facing away from the pump.  It was bad.  Put the new one in the freezer for a couple of hours before installing to check it.  Heater shut ifff when bay hit 44 degrees.  

[frankogrly]

I suggest you locate and check the snap disc. Mine is in the same bay as the heater.  My bay heater just quit and it was the snap disc. As I was getting ready to head into freezing temps removed, the snap disc and hot wired around it.

Frank O

01 Endeavor

[Hubert wells]

Thanks all for the info here , 

gives me some things to check out 

[Gary 05 AMB DST]

23 hours ago, Hubert wells said:

I have a 2008 Monaco Diplomat, can’t get my wet bay heater to work .

I installed a new heater nut still will not come on. The system heat light doesn’t work either , I’ve tried when the temps are below 40 degrees.

I have tried several times to locate the snap disc , but unable, even had it at Lazy days in Knoxville and they couldn’t locate it , they said some did not have them installed, could this be correct ?

thanks for any input .

I think they knew where it was, they just didn't want to mess with it. 

Gary 05 AMB DST

[saflyer]

OK, so have I found the snap disc? This is behind the wet bay panel.

I opened the heater and checked the fuse. It’s good. Am I correct that the heater connector wires are red-positive power, black-ground and small white in middle should be 12v positive from snap disc. I tried connecting red and white wires to positive on a battery and black to negative and nothing happened but I was just holding them by hand so I might not have made good contact.

Edited November 27, 2022 by saflyer

[Gary M]

Just now, saflyer said:

OK, so have I found the snap disc? This is behind the wet bay panel.

I opened the heater and checked the fuse. It’s good. And I correct that the heater connector wires are red-positive power, black ground and small white in middle should be 12v positive from snap disc. I tried connecting red and white wires to positive on a battery and black to negative and nothing happened but I was just holding them by hand so I might not have made good contact.

That’s it!!! Jump the snap disc to see if it runs and heats up. Mine ran but did not heat till I changed the fuse.

[jacwjames]

Yup, that's it. 

I just pull both the wires off the terminals and use a male to male spad connector to test.  Flip the system heat switch on and see if the heater runs.

[Tom Cherry]

OK....making PROGRESS.  You have, I THINK, the older (not messed with inside by the unknowing lead by the unwilling and chased by their lawyers).  Your Cargo Heater should be FINE.  Read my posts (OK...a lot of them).

Put GROUND to Black.  You need a good source of POWER.  Hook up a wire to your House or Chassis.  That positive goes to the RED.  OK....RED (that powers the HEATER) and BLACK (Ground).  The OTHER wire, white or Yellow.....is the THERMOSTAT.  You then need a SECOND wire from the battery.  IF you put 12 VDC on the Middle (white or yellow), that is the same as providing control or thermostat voltage.  BINGO....it should work.  It draws 20 amps, so just let it run and get a little warm.....then unhook.

NOW, if that works, then you have a control problem. If I were a BETTING person, I would bet that the RED wire Corroded terminal on the Snap Disk is bad.  If you want to test....do this.  USE your VOM.  Find the Cargo Heater Plug.  Put one test lead in the BLACK.  That is GROUND.  NOW, with the SERVICE HEAT switch OFF upstairs, you will have NO Voltage on the RED terminal on the Snap Disk.  Turn ON the Switch.  BINGO, that is the Control Power.  Test it.  THEN look at the OTHER side of the snap disc.  There are TWO wires.  ONE goes to the Heater (probably the YELLOW but WHO KNOWS....the color codes that I read are for a different year)....and the OTHER goes to the Pilot or INDICATOR light up stairs. I can't tell WHAT the surface is for where the Thermostat is mounted.  BUT, it IS the SNAP disk.  

NOW, you have measured the voltage.  NOW, you can do something SIMPLE.  Use a paper clip.  Take a PICTURE first.  If you jumper the RED to the Blue and YELLOW, then go back to the heater pigtail (on the MH SIDE). You will have VOLTAGE coming from the Middle (yellow or white wire).  THAT is the Trigger or Thermostat signal.  If you have 12 VDC there after jumpering the terminals....you have EITHER a bad Snap Disk or a Corroded Terminal. Taking it off and doing the melting ice test is the only way to tech it.  You can buy a NEW Snap Disk...

https://www.comstatinc.com/snap-disc-thermostat-p-24-l-en.html

Yours is SUPPOSED to be ON @ 40 +/- 6 and OFF at 55 +/- 6.  FIVE degrees ain't a big deal...

https://www.amazon.com/Thermostat-Switch-Circuit-Large-Flange/dp/B0026S6WGK/ref=sr_1_36?crid=39EZ17EMVE934&keywords=55+degree+snap+disk+thermostat&qid=1669590523&sprefix=55+degree+snap+disk+thermostat%2Caps%2C230&sr=8-36

This one would WORK as well, IMHO....I would NOT mount it.  I would suspend it from the ceiling.  That is the way mine is done...

Also from an IRV2 Post.

I did some digging.Senasy now makes the snap disk. Part # 2511L002-2123 or 2511L007-2123.They have on Amazon and also Mokey International.
Mokey about $10.00. Hope this helps you out.

OK....I googled the above....here is the latest PN from AMAZON  Senasys Snap Disc Thermostat Switch - Circuit On at 35°F and Off at 45°F - Large Flange, Part Number 2511L002-2132 

https://www.amazon.com/Thermostat-Switch-Circuit-Large-Flange/dp/B0026S6WGK/ref=sr_1_3?crid=302PLUW537YHG&keywords=senasys+snap+disc+thermostat+switch&qid=1669590913&sprefix=Senasy+ther%2Caps%2C173&sr=8-3

https://www.amazon.com/Thermostat-Switch-Circuit-Large-Flange/dp/B0026S6WGK/ref=sr_1_3?crid=302PLUW537YHG&keywords=senasys+snap+disc+thermostat+switch&qid=1669590913&sprefix=Senasy+ther%2Caps%2C173&sr=8-3

[saflyer]

48 minutes ago, Tom Cherry said:

OK....making PROGRESS.  You have, I THINK, the older (not messed with inside by the unknowing lead by the unwilling and chased by their lawyers).  Your Cargo Heater should be FINE.  Read my posts (OK...a lot of them).

Put GROUND to Black.  You need a good source of POWER.  Hook up a wire to your House or Chassis.  That positive goes to the RED.  OK....RED (that powers the HEATER) and BLACK (Ground).  The OTHER wire, white or Yellow.....is the THERMOSTAT.  You then need a SECOND wire from the battery.  IF you put 12 VDC on the Middle (white or yellow), that is the same as providing control or thermostat voltage.  BINGO....it should work.  It draws 20 amps, so just let it run and get a little warm.....then unhook.

NOW, if that works, then you have a control problem. If I were a BETTING person, I would bet that the RED wire Corroded terminal on the Snap Disk is bad.  If you want to test....do this.  USE your VOM.  Find the Cargo Heater Plug.  Put one test lead in the BLACK.  That is GROUND.  NOW, with the SERVICE HEAT switch OFF upstairs, you will have NO Voltage on the RED terminal on the Snap Disk.  Turn ON the Switch.  BINGO, that is the Control Power.  Test it.  THEN look at the OTHER side of the snap disc.  There are TWO wires.  ONE goes to the Heater (probably the YELLOW but WHO KNOWS....the color codes that I read are for a different year)....and the OTHER goes to the Pilot or INDICATOR light up stairs. I can't tell WHAT the surface is for where the Thermostat is mounted.  BUT, it IS the SNAP disk.  

NOW, you have measured the voltage.  NOW, you can do something SIMPLE.  Use a paper clip.  Take a PICTURE first.  If you jumper the RED to the Blue and YELLOW, then go back to the heater pigtail (on the MH SIDE). You will have VOLTAGE coming from the Middle (yellow or white wire).  THAT is the Trigger or Thermostat signal.  If you have 12 VDC there after jumpering the terminals....you have EITHER a bad Snap Disk or a Corroded Terminal. Taking it off and doing the melting ice test is the only way to tech it.  You can buy a NEW Snap Disk...

https://www.comstatinc.com/snap-disc-thermostat-p-24-l-en.html

Yours is SUPPOSED to be ON @ 40 +/- 6 and OFF at 55 +/- 6.  FIVE degrees ain't a big deal...

https://www.amazon.com/Thermostat-Switch-Circuit-Large-Flange/dp/B0026S6WGK/ref=sr_1_36?crid=39EZ17EMVE934&keywords=55+degree+snap+disk+thermostat&qid=1669590523&sprefix=55+degree+snap+disk+thermostat%2Caps%2C230&sr=8-36

This one would WORK as well, IMHO....I would NOT mount it.  I would suspend it from the ceiling.  That is the way mine is done...

Also from an IRV2 Post.

I did some digging.Senasy now makes the snap disk. Part # 2511L002-2123 or 2511L007-2123.They have on Amazon and also Mokey International.
Mokey about $10.00. Hope this helps you out.

OK....I googled the above....here is the latest PN from AMAZON  Senasys Snap Disc Thermostat Switch - Circuit On at 35°F and Off at 45°F - Large Flange, Part Number 2511L002-2132 

https://www.amazon.com/Thermostat-Switch-Circuit-Large-Flange/dp/B0026S6WGK/ref=sr_1_3?crid=302PLUW537YHG&keywords=senasys+snap+disc+thermostat+switch&qid=1669590913&sprefix=Senasy+ther%2Caps%2C173&sr=8-3

https://www.amazon.com/Thermostat-Switch-Circuit-Large-Flange/dp/B0026S6WGK/ref=sr_1_3?crid=302PLUW537YHG&keywords=senasys+snap+disc+thermostat+switch&qid=1669590913&sprefix=Senasy+ther%2Caps%2C173&sr=8-3

Thanks Tom. You’ve put a lot of effort into this and I appreciate it.

I was going to ask about the corroded post on the snap disc.  BTW it’s located on the plastic cover over the frame rail (I believe)and behind the toilet pipe to the black water tank. It’s only accessible two ways, through the hole that the tank quantity indicator leaves when it’s pulled off or removing the entire wet bay panel, not something I care to do. The first access, though can only be done with one arm and I can’t see in the cavity with my arm in the hole. I will have to attempt to unscrew the snap disc from the wall blindly and certainly can never get it reinstalled. But that’s OK, though. Like you said it can just dangle. I don’t know if the leads are long enough to get both hands in to reconnect it, though. But I’ll give it a try.

This all reinforces my feelings about designers.

[Tom Cherry]

7 minutes ago, saflyer said:

Thanks Tom. You’ve put a lot of effort into this and I appreciate it.

I was going to ask about the corroded post on the snap disc.  BTW it’s located on the plastic cover over the frame rail (I believe)and behind the toilet pipe to the black water tank. It’s only accessible two ways, through the hole that the tank quantity indicator leaves when it’s pulled off or removing the entire wet bay panel, not something I care to do. The first access, though can only be done with one arm and I can’t see in the cavity with my arm in the hole. I will have to attempt to unscrew the snap disc from the wall blindly and certainly can never get it reinstalled. But that’s OK, though. Like you said it can just dangle. I don’t know if the leads are long enough to get both hands in to reconnect it, though. But I’ll give it a try.

This all reinforces my feelings about designers.

Think out of the BOX.  Can you get a LEAD from a meter in there.  That was NOT clear.  If you can test as I suggested, then just abandon the old snap switch.  Unplug the leads and then make a Jumper to them and hand the disk where it is effective in the middle. All you need is a ratcheting crimper and some terminals....stuff that MOST of us have and carry as Monaco did a poor job.  So, you make up a 12" or so....Male and Female jumper.  That goes to the RED line.  You may a Y Fitting (two MALES) and plug in the Blue and Yellow.....then that has a Female on the end....which goes to the new Switch....  BINGO...get rid of it.  

Just an idea....I would TEST the Heater using the Plug on it and taking it around to the battery bank.  If it works....then Pull off the wires....and make a Y Jumper.  I would NOT unscrew it.  Once you have the wires when you can use spade or female ends, extend them as needed....

Have FUN...

[Happycarz]

Could what you think is a plastic cover over the frame rail be a holding tank? 

[saflyer]

On 11/29/2022 at 4:32 PM, Happycarz said:

Could what you think is a plastic cover over the frame rail be a holding tank? 

Took another look in the wet bay. I identified the potable water tank and the top of it is well below the snap disk. I do believe it’s mounted to plastic covering the frame rails.

Thanks