Improving Dometic fridge performance - Montana Owners Club

sapest · 07-07-2016, 07:58 AM

We have a one door RM 2862, original equipment in our '06 3400RL, set a "3". The cooling unit was replaced with an aftermarket unit about 4 yrs ago. Internal 12V fan blowing on fins. Have confirmed outside fan works as needed. Boiler and absorber temps approx. the same, which I believe means fluid circulation is good. Just before the fluid makes the last bend before entering the external fins at the top of the cooling unit, the tube temp is about 140F. After the fins, about 90F.
The internal fridge temp is about 44F. If I raise the fridge setting to 4, I will see ice forming on the fridge fins,(takes a couple of days) but the fridge temp may drop only one degree.
Before I start looking at baffles, fans etc to improve the cooling unit side of things, I am wondering about the door seals. They are clean, no cracks, and on the dollar bill test, I do get some resistance. The black metal frame that the door seals to is cool to the touch, temps measure about 64/5F all around the door.
My question - is 64/5F normal, or is this the issue?
I don't want to take on replacing the door seal unless I am sure that's the solution.
Any suggestions to improve the seal without replacing it appreciated.
Thx
-Steve

**Rondo** · 07-07-2016, 08:51 AM

To possibly soften the seal around the door and etc, you might want to try and get some Aero 303. I use it on the outside seals of the slides and it keeps them soft and pliable for a good seal all the way around. You also said you have a fan on the inside, I believe, and it is blowing on the fins. This could be the problem also. If the air is blowing on the inside fins it could be sensing the cooler temp thus not cooling the refrig as it should. You also could have a bad thermistor on the fin or the thermistor has slid down the fin on the inside and not letting the unit cool as it should. There are several posts on the thermistors here on the Forum. Go into the archives and search engine at the top of the page and do a search on the thermistors or cooling problems on frig. Let us know what you find or come up with.

jcurtis934 · 07-07-2016, 09:40 AM

You should see frost on the fins as this is moisture in the air when you open the door...ie, warm air entering fridge. The tray below takes care of the water from defrost cycle (heating of the fins at some time period). An internal fan to even out fridge temps sounds good, but all that stuff in the fridge does a lot to block airflow. I have never went that route. Postion of thermister on fins important, setting of control important. I ran my dometic at five and now run my norcold in monte at five most times. If you have the install docs on the fridge, compare them versus what you see through the top vent outside just to be sure the factory did what they should have done. John

dieselguy · 07-10-2016, 03:45 PM

Assuming the fridge is mechanically operating correctly and the wood baffling behind the fridge has been installed correctly ... the best thing you can do for an in-slide fridge is add an external fan(besides the stock one)and get a control that activates the external fans quicker. This can be done by a simple toggle switch or by adding an ARP control system. They have a website and are very helpful with self installs should a problem arise. Or although a bit redneck ... just prop up a small floor fan blowing into the lower external fridge vent.

TLightning · 07-11-2016, 12:25 PM

Best option is put in a residential refer.

dieselguy · 07-11-2016, 04:32 PM

I respectfully disagree in it being the best option as it depends on your RV use. There are lotsa of us that don't need a mega sized residential fridge that seems to be the growing norm. Some floor plans eliminate the pantry when a residential fridge is optioned out. There are those of us who don't want to mess with in inverter and multiple batteries and would like the ability to run the fridge on propane as the need arises. Gas absorption fridges have been around for a lot of years serving many owners. The biggest stack of cards played against them in the last say 12 years has been putting them in the slide outs. The natural flow of cooling air that used to be in a non slide out fridge is greatly reduced in an in slide fridge. That's why you need to get more external help (aux fans) to replace that air flow.

sapest · 07-11-2016, 04:41 PM

Thx to all for your thoughts and suggestions.
What I am looking for is the answer to one question - what temps do similar fridges exhibit around the metal door frame?

Hold your debate about which type of fridge is better for another thread plse.

-Steve

dieselguy · 07-12-2016, 04:22 AM

I've had several RV's and all fridges have formed ice on the internal fins to some degree ... a bit of frost/ice is normal. I've never been able to run on (3) Dometic nor Norcold and keep them as cool as I want (36 - 38F). If you have resistance from sliding a dollar bill all the way around the door, that tells me your door is sealing properly. I can't answer your question to temp around the door frame, but feeling around my stick houses' residential fridge's door frame ... it is cool to the touch. Actual boiler temps should be in the 360F range on a hot day. The temps on the bottom two runs of the absorber tubing should run about 120F or better during the day. Just because your 110VAC electric heating element is making heat doesn't necessarily mean it is operating properly for your unit. Check the amp draw of the element and note the voltage at the plug near your fridge. Multiply the two together to get the watts. Check to see what your units watt requirement is for the heating element and compare. Your calculation should be + or - 10% of requirements. You should be able to do better than 40F especially if you take a temp reading first thing in the morning.

sapest · 07-13-2016, 08:31 AM

Thank you for the suggestions and insight dieselguy.
Watts are in the 314-309 range when boiler is heating.
The fridge label indicates 2.7 amp draw, I see 2.66, so that seems correct, but as I have aftermarket cooling unit, I have no idea what the watts draw should be.
The Dometic service manual I found here (http://www.dometic.com/QBankFiles3/E...nual_17606.pdf) states a 2862 can pull up to 325 watts, so my number also seems in the right range.
Perhaps I just need to run the unit at (4) and watch the icicles on the fins come and go.
I will be looking at airflow across the cooling unit, I can see some issues already, and am thinking squirrel cage fans.
-Steve

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