Fridge warming up overnight

[MalibuDave42]

Dometic DMR702. No error codes. On shore power or propane, fridge\freezer cools down. Seems to work great during the day. Temps 34'ish and -2.5'ish, right on target. Overnight, the temps go up a bit.. 42-45, 8-10. As the day warms up, the fridge gets going to bring the temps back down.

- I did the "unplug from controller board, 120v directly plug in the AC heater" test - brought the temp right in line.
- I replaced the tank pigtails and the switching propane regulator (it was not putting out enough propane to support all devices). Tests out fine now.
- I replaced the igniter\thermocouple.. was time to replace it.
- The flame is a nice blue quarter sized -- looks great.

It seems something is telling the controller, the temp is good. Any thoughts are greatly appreciated.

[MalibuDave42]

Yes, nighttime temps in the 20's to lower 30's.

I did a bit of internet digging after you posted about ambient temps. The issues range from "no problems to -20C" to "I had issues around 40F." Thinking about the physics side of this problem, it makes a great deal of sense ambient temperature affects operation. One possible conclusion of the variable results I see posted to the internet is installation matters - aka the airflow of a given install affects the operational temperature.

100 watt bulb sounds nice, but a no-op for no-shore-power use. Blocking off lower vent openings is worth a try. Thanks for the tip.

[GDS-3950BH]

MalibuDave42 wrote:
My clip-the-tip still has not arrived. ?? I've been using the fridge as is. It's limping along. Fridge temp goes to the low 30's then sails into the mood to high 40's. What are your thoughts on this temperature pattern:

Where are you and what are the nighttime ambient temps outside? Once they're below 45 and dropping an absorption fridges efficiency drops almost exponentially because it can not generate enough heat. Try putting an incandescent light bulb, preferably 100 watt, in a socket in the lower compartment or block off the lower vent openings one at a time to see if the interior temp drops.

[MalibuDave42]

My Articca Thermistor (snip-the-tip) has finally arrived. Since I could not test the factory installed, I am installing it.

The directions say to mount it on the side .5-.8 inches from the fins. The factory thermistor is on the back wall about 6 inches below the fins.

Does anyone have any experience with mounting location?

[MalibuDave42]

Back home, food out of the fridge, time to run the thermistor test.

Old-Biscuit says "Unplug the thermistor leads from lower circuit board (P2 connector at J3 --- S/B white leads)"

Not sure what "P2 connector" means, but at J3 on the lower board there is 1 connector with a white-shielded wire with 2 conductors inside. This 2 conductor wire runs up the back of the fridge and disappears.

I turned off the power, pulled the wire from the connector. Turned on the power, turned on the fridge. The fridge is reporting a "thermistor has an error" error code. (must be the right wire)

Unfortunately, the fridge will not start on propane nor 120v with this error code.

What should I do? I apparently can't run this test.

[wopachop]

Edit: so wrong. Sorry about that.

[wopachop]

Old-Biscuit wrote:

SO......
Unplug the thermistor leads from lower circuit board (P2 connector at J3 --- S/B white leads)
Run fridge overnight w/o thermistor sensing and fridge temps should go down and stay down
If they do replace the thermistor

[MalibuDave42]

I have not tried the thermistor test. I was planning to just replace it. Since I've left on a trip and the snip never showed.. Maybe I need to do that test.

What happens if I disconnect thermistor and just run it without? Will the fridge just keep running without a break? How long do I run the test for?

[wopachop]

1. The thermistor is not sending the proper reading.
2. The circuit board is not interpreting the thermistor correctly.

Hope the snip tip works once its finally shows up.
Not sure if you answered. With the thermistor disconnected does the fridge still stay off long enough to hit the mid 40s?

[MalibuDave42]

My clip-the-tip still has not arrived. ?? I've been using the fridge as is. It's limping along. Fridge temp goes to the low 30's then sails into the mood to high 40's. What are your thoughts on this temperature pattern:

[Edd505]

Old-Biscuit wrote:
That model does not have 'defrost' mode
That model is equipped with an automatic Low Ambient Control (LAC) function
*turns food compartment light ON when ambient air temps drop below 50*F ---- no on/off switch (light causes a heat load so thermostat calls for longer heat cycles/colder temps
That model only has 3 temp setting.....narrow range control

You have proven cooling unit functions properly (Direct wiring of element)

SO......
Unplug the thermistor leads from lower circuit board (P2 connector at J3 --- S/B white leads)
Run fridge overnight w/o thermistor sensing and fridge temps should go down and stay down
If they do replace the thermistor

Snip-The-Tip Rheostat thermistor replacement

This is your resident expert, he's helped me with a Norcold cooling issue. Always good advice.

[MalibuDave42]

Old-Biscuit, a question about your Thermistor test. When you unplug the Thermistor, the control must be reading the temp as "too warm, keep running." Is this correct? If yes, does this mean the boiler\refrigerant runs continuously until there is manual intervention (aka it's manually turned off)?

How will this test answer the question about not staying cold overnight?

WRT to Snip-the-tip. It will be no problem to install. But, how will I know if it is working? Should I monitor the temp, keep adjusting the dial until the temp is correct?

Thanks for your insights

[Old-Biscuit]

wa8yxm wrote:
I would be inclined to think the outside coils and stack need cleaning.
This is described more or less in your owner's manual. I've never done it.

Sun heat on the outside increases air flow up through the coils is my guess

I'd remove upper and lower covers, blow air DOWN (Carefully and straight) to clean the coils Make sure the coils do not end and close off.

Stack cleaning is described in the manual I hope.

OP posted fridge works great during daytime BY+UT warms up at night
*night ---sun goes day ambient air temps drop

Re-read OPs 1st post

[wa8yxm]

I would be inclined to think the outside coils and stack need cleaning.
This is described more or less in your owner's manual. I've never done it.

Sun heat on the outside increases air flow up through the coils is my guess

I'd remove upper and lower covers, blow air DOWN (Carefully and straight) to clean the coils Make sure the coils do not end and close off.

Stack cleaning is described in the manual I hope.

[MalibuDave42]

For $29, I'm just replacing the thermistor. New snip the tip on the way. Back to you all soon. Thanks for the advice..

FWIW, I installed Fridge Defend by Arp with internal and external fans to provide more safety\control of the burner... lovin' that device