Dometic RM2510 Not Working On Electric

NuthatchBC · 07-18-2021, 05:12 PM

Oh boy, another problem with a Dometic fridge. I can see everybody cringing already. Seriously though, I've gone through a lot of diagnostics and still haven't found the problem so I do need some advice.
I've done checks at the AC outlet and get 117 vac.
I've checked continuity of the heating element and it's fine. It is also within spec as far as the resistance is concerned, 74.3 ohms.
In reading the manual, I see there is supposed to be a fuse somewhere but I can't find it. I think it's underneath the fridge cabinet. If so, it's inaccessible. How would I check that?
According to the schematic in the manual, the AC voltage is controlled by the switch on the front panel. How do I remove that panel so I can check the switch?

Standing by.......

Doug

gbaglo · 07-18-2021, 05:19 PM

At least you ( we ) don't have bunches of LED lights and circuit boards to fail.
I had the propane/off/elec switch replaced on my 2510. They had to pull the fridge.

Vermilye · 07-18-2021, 05:30 PM

I had thermostat problems 3 times with my DM 2510 in my 2011 17B. Two of the times it was electric, once propane. There is a diaphragm that the thermocouple feeds (mechanical, not electric) that opens & closes the gas valve, and operates a switch through a cam. In the electric failures, the cam jammed, keeping the switch open.

Unfortunately, the refrigerator must be removed to replace the thermostat (although I have seen one post where it was done in place - I don't see how that was possible). About a $60.00 part & if you have it done, 2 hours of labor.

It may not be your problem, but if both power & heating element check out, it is likely. There is no circuit board, although the multi pole switch could also cause the problem. Here is the manual for the DM 2510. Check page 14 for the circuit diagram.

NuthatchBC · 07-18-2021, 06:16 PM

I don't think it would be the thermostat if it works on gas, would it? When it's on gas, it works perfectly, keeping the temps right where they should be. I'm thinking the fuse, which isn't accessible, or the switch. I tried to take the front panel off to look at the switch but it looks like the door has to be removed and I ain't doin' that.

Doug

Vermilye · 07-18-2021, 07:06 PM

Quote:

Originally Posted by NuthatchBC

I don't think it would be the thermostat if it works on gas, would it? When it's on gas, it works perfectly, keeping the temps right where they should be. I'm thinking the fuse, which isn't accessible, or the switch. I tried to take the front panel off to look at the switch but it looks like the door has to be removed and I ain't doin' that.

Doug

Again, this may not be your problem, but a "bellows" is driven by the thermocouple in the refrigerator (not the one in the flame) opens & closes the gas valve AND through a mechanical linkage opens & closes an 120V AC switch in series with the heating element. The bellows valve (and switch) is used to control the refrigerator temperature.

In my case, the mechanical linkage failed - it still worked fine on gas. As far as I know, there is no fuse in the 120V line. If there is, it is not shown in the schematic & I've never seen it.

NuthatchBC · 07-18-2021, 09:00 PM

I agree, Jon. I don't think there's a fuse in there either. Funny the troubleshooting section of the manual would mention it as a possible problem. Well, if the fridge has to be pulled to continue this diagnosis, I'm going to have to call in an RV tech. I don't have the wherewithal to do that here.

Doug

rubicon327 · 07-19-2021, 11:30 AM

Doug:
PDX RV has a great webpage with many manuals that may be useful especially the service tips if you haven't seen it...
https://techsupport.pdxrvwholesale.c...ometic-rm2510/

I did find one video that shows replacement of the thermostat without removing the fridge but it does not look like fun:

https://www.youtube.com/watch?v=fjTloEDB6I0

The selector switch is buried behind the gas valve and as Glenn indicated it would most definitely require removal of the fridge.

Sorry I cannot be of more help. Thankfully I have not faced any issues (yet) regarding electric operation with our RM 2510.

NuthatchBC · 07-19-2021, 12:03 PM

Thanks for the info and the video. It MAY help if I find the intestinal fortitude to try that

I may have a way to see if the selector switch could be the problem. If I unplug the unit from the mains outlet and put one probe of an ohmeter on the 'hot' side of the plug and the other probe on the terminal block that connects the 'hot' to the heating element and turn the switch to "ELEC", I should be able to see if there is continuity in that line which would tell if the switch is working or not. Unfortunately, there isn't a way to test the other lead to the heating element because it passes through the thermostat first. If the switch works, the problem would most likely be the thermostat, like Jon says.

Doug

rubicon327 · 07-19-2021, 12:51 PM

Quote:

Originally Posted by NuthatchBC

I may have a way to see if the selector switch could be the problem. If I unplug the unit from the mains outlet and put one probe of an ohmeter on the 'hot' side of the plug and the other probe on the terminal block that connects the 'hot' to the heating element and turn the switch to "ELEC", I should be able to see if there is continuity in that line which would tell if the switch is working or not. Unfortunately, there isn't a way to test the other lead to the heating element because it passes through the thermostat first. If the switch works, the problem would most likely be the thermostat, like Jon says.

Based on what you describe I believe you would be checking continuity on the neutral. The hot or line passes through the thermostat and it looks difficult to intercept upstream of the thermostat based on the video. The connections appear to be buried at the back left of the thermostat unit (the last things he removed before pulling it out).

NuthatchBC · 07-20-2021, 03:00 PM

Yup, my mistake. It is the neutral I'd be checking. I know it would only test one side of the switch but at least I'd know that wasn't the issue is there's continuity there. And yes, I don't think there is any way to perform that test on the hot side unless the fridge is removed. I'd want to be d__mn sure the problem was underneath there before I'd go that far.

Doug

NuthatchBC · 07-20-2021, 03:45 PM

Quote:

Originally Posted by Vermilye

Again, this may not be your problem, but a "bellows" is driven by the thermocouple in the refrigerator (not the one in the flame) opens & closes the gas valve AND through a mechanical linkage opens & closes an 120V AC switch in series with the heating element. The bellows valve (and switch) is used to control the refrigerator temperature.

In my case, the mechanical linkage failed - it still worked fine on gas. As far as I know, there is no fuse in the 120V line. If there is, it is not shown in the schematic & I've never seen it.

So, trying to understand the workings of this fridge, in your case, Jon, it wasn't the actual thermostat that failed. It was some sort of mechanical linkage in the thermocouple. Is this correct?

In the video, the guy said he had turned the thermostat full on in both gas and electric modes when he tested his fridge and the next day it hadn't cooled at all. This would make sense if the problem was with the thermostat. In my case, the thermostat worked as it should when on gas but not on electric. I'm thinking there's something else going on with mine.

Doug

Vermilye · 07-20-2021, 05:08 PM

Again, in my case the thermostat worked fine on gas. After replacing it, I took the old unit apart. I'm not the engineer that designed it, but as far as I can tell, this is how it works:

There is a capillary tube that is attached to the cooling fins in the refrigerator on one end & a bellows in the thermostat. The bellows opens & closes the high flame gas valve AND through linkage, opens & closes a switch in series with the 120V heater element. The temperature control doesn't actually sense temperature; it changes the position of the bellows making it close sooner or later. In my case the linkage between the bellows & the switch for electric failed, keeping the switch open matter how expanded the bellows moved. It still open & closed the gas valve.

The way Reace determined that the thermostat was bad was to turn the temperature control up all the way - there was still no power to the electric heating element. According to him, dialing the temperature all the way up should always apply voltage to the heater element.

The link I gave for the thermostat may not be the correct one for the RM 2510; it is the one Google sent me to. I looked up what I purchased & it was #2007199009. In the photo at the Amazon link you can see the cam that adjusts the bellows linkage when turning the temperature control.

NuthatchBC · 07-20-2021, 05:47 PM

OK, I think I'm beginning to see how this works. I checked the schematic again and the series switch looks like it must be inside the thermostat since there is a 'B' beside it that denotes the thermostat. If there is a linkage problem like Jon describes, that's definitely above my pay grade. I'm still going to try and test both sides of the selector switch.

Doug

Vermilye · 07-20-2021, 05:52 PM

In the photo on the Amazon page, the switch is in the case on the right. You can see the ceramic body with the two terminals attached. The linkage goes between the main section & the switch.

rubicon327 · 07-20-2021, 06:54 PM

Quote:

Originally Posted by Vermilye

The way Reace determined that the thermostat was bad was to turn the temperature control up all the way - there was still no power to the electric heating element. According to him, dialing the temperature all the way up should always apply voltage to the heater element.

That is correct and may be helpful in troubleshooting.

NuthatchBC · 07-20-2021, 07:07 PM

Well, I managed to test the hot side of the 120vac line to the heating element and it had continuity, meaning the series switch inside the thermostat must be closed and the selector switch is fine. So, the problem must be in the part that Jon is talking about although I'm still having a problem understanding how that works. So far, I've done these tests with the 120vac shut off. Maybe I should do the one that Reace did and plug into 120 vac, crank up the temp control and see if I have anything at the heating element.

Doug

NuthatchBC · 07-23-2021, 02:33 PM

I'm happy to report that our RM2510 is now working on electric and I had nothing to do with it. Well, that's not quite true. In all of my fiddling with the connections in the fridge cabinet, I must have fixed something that was either loose or corroded or both. At any rate, the fridge is now cooling beautifully on electric.

Thanks to all who provided much appreciated help in this endeavour. I'll keep these posts handy in case this happens again.

P.S. Before it started working again, one my neighbors said that problem might be the heating element even though it checked good. He said as the element warms up, it could be opening up slightly which would cause it not to work. Anyone ever heard of this happening?

rotorbudd · 07-23-2021, 05:27 PM

If jiggling the connections seemed to fix it maybe you should put a wrench or screwdriver on all of them just to be sure everything is tight.
A high resistance AC connection can generate enough heat to start a fire. (think electric stove)

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