Dometic RM 2652 not cooling

[Kirk W]

First of all, download a copy of the RV2652 service manual from Bryant RV website. Next:

 

Heating Element: 39.5 (I know you said 44ohms was right but is 39.,5 ok) That is less than 10% differential and should be OK.

 

Thermistor: 4.79 at around 75 degrees & 11.25 when put into ice cold water

 

THERMISTOR

Disconnect the thermistor harness from the P2, 2-pin terminal on the lower circuit board. Place the thermistor in a glass of ice water, approxi-
mately 33°F to 35°F. Wait 2 to 3 minutes. You should get a reading of approximately 7,000 to 10,000 ohms.

Your readings there seem to be in k-ohms? If that is just ohms they are clearly bad. If that is k-ohms then it would be pretty close and likely OK. If readings were taken on the 20k ohm scale, then that is probably within acceptable range. The voltage sounds correct as it should be pretty close to what you read across the battery and the units are built to operate between 14v and 10.5v.

 

It sounds like the cooling unit may be failing. Are there any signs of yellow powder or sludge anywhere in the back of the refrigerator, inside of the outside access panel? That is one of the indications of a refrigerant leak, but the lack of yellow doesn't mean that it still works. They can fail for many different reasons. How old is the refrigerator? In my opinion it is seldom cost justifiable to replace a cooling unit unless you plan to do the work yourself because the cost is close enough to that of a new refrigerator to make it a better choice. Boiling inside of the boiler part of the cooling unit is normal, but you usually can't easily hear it happening. The absorption refrigerator must boil the refrigerant for one to work.

 

Your brother is wrong about the repair of the cooling units, or at least I have never heard of anyone who does this. It is possible but most people buy a new cooling unit and install that as the labor cost of repairs would be excessive, if you could find someone who was willing to do the work. As for what you are looking at, I'd need to see a picture to say what it may be that you see.

[heebeha]

I don't see any yellow muck in the back or in the fridge. the camper is a 1998 so I am sure its that old.

I read that carbon/ammonia cubes buildup could be the issue. Is there a way to break the carbon/hard ammonia up maybe when all the pipes are hot I could tap on them all and loosen it, break it up?

 

I cant believe that I can run some kind of solution through maybe some pressure and blow out the lines. It seems silly to me that it is not serviceable.

 

What is this threaded cap on the tank for if its not to serviced the cooling unit lines?

[Kirk W]

I have never heard of any carbon in the coolant system, but it can be a problem in the flue, as could rust. It would be a good idea to clean the flue as best you can. I'd also apply a shop vacuum to the lower end and all around the burner area to get rust, bug nests, and any soot build up out as best you can. If you look in the service manual it may address disassembly of the flue but if you do that be sure to get the baffle back into it the way that it is now.

 

The refrigerant is a mix of water, ammonia, anti-corrosive chemicals(the yellow stuff), and some hydrogen. What typically hardens inn the tubes is actually the anti-corrosive material in most cases. Sometimes tapping on the tubes with a hard rubber hammer will help but usually not for a long time.

 

As to fixing it yourself, you probably won't make it any worse, since it isn't working but you would also be the first that I know of to succeed in doing it yourself. It isn't as simple as just draining it out and pouring something back into the tank since they are purged of air, and the proper mix of ammonia, water, and chemicals isn't shared with the public. Once you get everything back in, you then need to charge the cooling coils with the proper amount of hydrogen to be dissolved into the coolant. There are several RV techs who frequent these forums and none of them do repairs on the cooling units in the field.

[heebeha]

I took a photo of the OHM reading at room temperature and the OHM meter so you can see how I have it set to take the reading. Please let me know your thoughts. Could a bad Thermistor cause it not to get cold? Anyway to bypass it? Could bad ventilation be causing it not to get cold? I pulled my fridge out half way to try and get some separation from the wall as it was pretty tight. I have water damage I am repairing, including the wall in the fridge area.

 

[Kirk W]

That shows 6.23 kΩ which is 6,230 Ω and that is reasonably close to the 7,000 Ω that they are calling for. Your refrigerator has a "fail safe" mode built into it for thermistor failure in which it will go into constant cool and the symptom of that is things freezing, even in the chill box area. If the system should detect a resistance in the thermistor that is outside of normal operating range it will go into a constant cool mode in the belief that less food is harmed by freezing than would be from things getting too warm and the frozen food thawing. In other words, I have never heard of any case with RV refrigerators in the past 25 or more years that a failed thermistor would cause it to fail to cool. All recent models that I know of will freeze things if a thermistor fails. The fail safe mode came into common use in the 80's if memory serves.

 

I set the OHM meter to 20k and got these readings:

 

Heating Element:
39.5 (I know you said 44ohms was right but is 39.,5 ok)

I just read you post again and realized something that I failed to pick up previously. If your meter was set to the 20k range and read 39.5 that would not be 39.5 Ω. That reading must have been taken on a different range setting. The reading would be proper if your meter was set on the 200 Ω range. Notice that in the picture which you sent, there is a small kΩ to the right of the reading and a 20 under it. For the resistance of that heating element to be correct, the display should show 39.5 and a small Ω to the right side of the display. You may want to check that reading another time. If the display has a reading of 39.5 with a kΩ beside it, that indicates that your heating element is bad and should be replaced.

 

You have not said, but have you tested the refrigerator to see if it will cool on propane? It will need to have a 12V supply in order to work properly with either source of heat. If it does not have 12V-dc available, it will not operate on any mode as the controls are powered by 12V-dc in order to be able to use the same ones with either electric or propane mode and it makes the auto mode possible.

 

Do you have 12V-dc power to the refrigerator? If so, is that voltage between 11 & 14V?

[heebeha]

The fridge doesn't get cold inn propane. It acts the same on 110 and propane, as I initially described. It has 12.9 volts DC to the control panel.

 

Should I try taking it out and flipping it upside down before I buy a refurbished cooling unit?

[Kirk W]

It won't hurt anything. Might be worth a try.

[heebeha]

So what do you think. Get her hot before i flip it over and bang on pipes?

As I said earlier, the propane and 110v get the boiler and Absorber tank and absorber coils get hot.

[Kirk W]

it probably don't matter & I wouldn't worry abiut heating it up. It operated on convection flow so hot is probably not helpful. If the problem is an obstruction, that might help for a time but isn't likely to be a permanent cure.

[heebeha]

I flipped the fridge a couple times. I heard a lot of liquid moving back and forth. Running it now direct on 110v. No change...

 

Which company do you recommend to buy a refurbished cooling unit from? There are several companies online that sell them for the same price.

$425 plus $40 shipping and contingent upon core return

 

http://www.rvcool.com/Dometic_Pricing.htm lifetime warranty

 

http://www.rvrefrigerator.net/dometic_pricing1.htm lifetime warranty (looks like the same company)

 

http://rvcoolingunit.com/RM2652-Dometic-Cooling-Unit-605a-P10760.aspx AMISH - 3 year replacement warranty and a 5 year for leaks

 

http://www.rvfridgehouse.com/CUPricing.htm Five (5) YEAR LIMITED WARRANTY

 

 

NEW: $630

http://www.arcticoldstore.com/dometic-rm2652-brand-new-manufactured-cooling-units-lifetime-warranty/ lifetime warranty

Edited May 31, 2016 by heebeha

[Kirk W]

I have no experience with any of them so perhaps someone who has will join in.

[heebeha]

Who have you bought from Kirk?

[heebeha]

I pulled out the bad Cooling unit the other day and discovered a lot of corrosion on the aluminum plates.

What can I use to repair corrosion on the freezer aluminum plate and refrigerator fins back plate on my Dometic rm2652? I bought a new cooling unit, its in route, I want to get the fridge ready to go back together today. Help

the aluminum is pretty badly corroded, with a couple holes that go all the way through and deep crevices. I am hoping there is a product like JB weld I can use to fill in the holes and deep crevices.

Attached are photos to help explain what I am referring to and show how bad it is.

 

 

 

 

 

[I'mdonewiththis forum]

I can't tell you what to use on the badly corroded aluminum, but I would definitely think about something like this for the installation: http://www.homedepot.com/p/Ideal-NOALOX-4-oz-Anti-Oxidant-Compound-30-026/202276208

[pugsly]

I would try to clean the aluminum up but not patch it - it is functioning as a big heat sink and patching with a different material will probably not improve matters. Having a clean surface and good thermal transfer is important. I would probably use thermal mastic not the anti-oxidant, but you do need to use something applied to clean and bright aluminum. I would use a 3M/scotchbrite surface conditioning disc (or similar from Home Depot, etc) for surface preparation.

[heebeha]

Should I fill the cracks and gaps on that plate with the thermal mastic? I am, getting a tube with my new cooling unit. There are 2 holes that go all the way through the back plate that I need to fill don't you think?

[heebeha]

Looking at a few aluminum filler:

 

http://www.globalindustrial.com/p/tools/Applicators/Caulk-Sealants/metal-patch-fill-50345-3-oz-tube?infoParam.campaignId=T9F&gclid=CLzJ9qDhr80CFdgSgQod3wMGCA

 

http://www.autozone.com/sealants-glues-adhesives-and-tape/epoxy-compound/permatex-3-1-2-oz-tube-liquid-metal-filler/552885_0_0/

 

http://www.autozone.com/sealants-glues-adhesives-and-tape/epoxy-compound/blue-magic-qs-high-temperature-metal-repair-trilingual/515553/?_requestid=3270319

 

I know I need to fill the voids. Cant be good to leave it as it is now

 

Thoughts?

[Darryl&Rita]

It's simply a way to move heat from the tubing to the air. Don't worry about the missing Al, as much as where did the missing material go?

[heebeha]

I wire wheel brushed both plates so the aluminum is shiny, removed all the corrosion and put aluminum tape over the holes. What do you think, will the tape cause more harm than good?

See photos of what I did.

 

My new cooling unit comers today. I would really appreciate some feedback ASAP today. Please any help will goa long way.

Before and after photos can be seen here: http://zetal.com/98fleetwood/dometic-refrigerator.html

 

 

 

 

Edited June 24, 2016 by heebeha

[j2catfish]

One thing that has not been mentioned: there is a what I call a bi-metal switch located on the heat tube that can and will "pop" and that will cause a no cool condition. The propane will continue to provide the heat but the open switch will not allow the frig to operate as advertised. The switch is located just above the the burner. It has two wires attached to it and has a manually re-setable button on it. It does not cost anything to at least try to re set it.

My frig is a Dometic 1292 but your model may have the same switch.

Good luck, RV refrigerators are not fun to troubleshoot!

Catfish

[heebeha]

So, just fill the holes with mastic even though they wont touch the pipes, take off the aluminum tape in put over the crevices and holes?

[leot]

I have the same refrig, same problem, lights on at control panel, 110 and propane work, chimney gets hot but system doesnt cool, was 2 years old in May, no evidence of amonia or yellow powder, refrig was only used about 20 nights and is like new. That little bimetal switch seems to have continuity in both positions? is there a way to bypass that to see if that is the problem? I checked the thermister and it has the correct OHMs , the control panel has correct volts. After only 2 years it seems like the refrig was defective?? Any help is appreciated.

[Kirk W]

Welcome to the Escapee forums! We will do all that we are able to help.

 

The first thing I'd suggest is that if you don't have a copy of the service manual, visit Bryant RV and download a copy of it. I'm not sure what bimetallic switch you are referencing?

[leot]

I downloaded the service manual. The switch I referenced is mentioned by j2catfish above.

[Kirk W]

I don't seem to find that switch or thermostat on the schematic. If you can get to the connections to that switch or thermostat with some sort of jumper, it should harm nothing at all to jumper across it, thus insuring that it is electrically closed. I think this may be a good way to see if it is the problem.

 

I wonder if that device might be a part of the safety recall that Dometic had several years back? That might explain the reason it isn't on the schematic we are using. I'll try to see if I can find someone who knows the answer to this. If that is a part of that recall, it could be of grate importance.