Intermittent Problem with Fridge

[mondmn70]

I have a Dometic (RML 8555) gas/12V/120V fridge that occasionally stops working on gas or 120V (not sure about 12V since seldom us it). It only happens a few times a year and can happen at anytime - either stationary or traveling. The fridge has an automatic setting which uses gas for travel and 120V when plugged in. I have taken it in for service since it is still in warranty (few more months) but of course it cannot be duplicated.

The symptoms are that the temperature will start to rise while either stationary or traveling. When on gas, the flame is still burning but just does not sound as if it is burning at as high a rate as when the fridge is operating properly. When on 120V all the other 120V equipment continues to work normally. So it seems that the fridge is just not calling for cooling when it should be. Switching between gas and 120V (when connected) will usually fix the problem after an hour or so but can take longer on occasion. When this first started, the fridge beeped when the temperature started to increase but has not done this in the most recent episodes.

Any suggestions on a circuit board or sensor that could causes this to occur with both gas and 120V that would be easy to change and maybe fix the problem?

Thanks for your help.

Mike

[mondmn70]

dougrainer wrote:
The rear cooling is probably your problem. What you need to do is verify that when the temp rises and you do have flame or the 120 is hot, IF you do not hear the fan then the fan tstat is intermittent. Common problem for Dometic rear fan tstats to fail. What you can do if you have easy access to the top outside side vent, remove it and you will see the fan tstat on the condenser coil, Install a 2 wire jumper to the tstat and run down the back side to the rear bottom. Then connect those wires together to run the fan continuously when this problem happens. You can also leave the jumper wire connected to run the fan 24/7 and your refer will be more efficient. Also, make sure the area above the condenser fins(ceiling) has a baffle or curved roof baffle to direct all the air out of the upper vent door. ANY gap that goes above the rear access door will allow hot air to stay trapped and you will lose some cooling efficiency. If not properly roof baffled, then when the fan fails to run, the convection hot air cannot be driven out the top and will cause the cooling unit to not operated correctly. Doug

I don't think it is outside cooling. This erratic cooling only occurs occasionally and can happen when outside temperatures are in the 40's or 50's and the exterior exhaust fan continues to work when needed. When the cooling drops off, I have measured a decrease in the condenser temperature with an IR thermometer which suggests that the heating section is not boiling up enough vapor. Then within an hour or two the fridge sometimes resumes cooling without any significant outside air temperature changing. I think the suggestion that the temp thermistor works erratically or something similar is more likely.

Mike

[down_home]

.....

[dougrainer]

The rear cooling is probably your problem. What you need to do is verify that when the temp rises and you do have flame or the 120 is hot, IF you do not hear the fan then the fan tstat is intermittent. Common problem for Dometic rear fan tstats to fail. What you can do if you have easy access to the top outside side vent, remove it and you will see the fan tstat on the condenser coil, Install a 2 wire jumper to the tstat and run down the back side to the rear bottom. Then connect those wires together to run the fan continuously when this problem happens. You can also leave the jumper wire connected to run the fan 24/7 and your refer will be more efficient. Also, make sure the area above the condenser fins(ceiling) has a baffle or curved roof baffle to direct all the air out of the upper vent door. ANY gap that goes above the rear access door will allow hot air to stay trapped and you will lose some cooling efficiency. If not properly roof baffled, then when the fan fails to run, the convection hot air cannot be driven out the top and will cause the cooling unit to not operated correctly. Doug

[Padlin]

Mike
Join the party. RML8555's as well as it's smaller 4.3 cf sibling were installed in many Escape trailers, they all have the same problem you are talking about. Hundreds of pages on it.


For your reading pleasure.
Fridge problems
Fridge problems II
Folks attempting fixes
More of the same

Dometic is well aware of the problem, make sure you bring yours in for service while still under warranty in case they actually find a fix for it. At the moment we're waiting to see if Dometic comes out with a fix, supposedly they are getting ready to come out with a new door for them. Meanwhile some folks have taken it onto themselves trying a multitude of mods to try and alleviate the problem. Awaiting results as folks travel to the south for the winter, although nothing has really worked to this point. Last I read Dometic is designing a new door. Escape went to a 2 door model of the same fridge RMD8555 which supposedly works better.

[mondmn70]

dougrainer wrote:
1. Temp rise on your model will not cause any indication or beeping.
2. IF there is a failure, you will get a flashing LED stating what has failed
3. Should the door be kept open for too long
(more than 2 minutes), the blue external
LED starts flashing until the door is closed.
Only with AES models an acoustic signal is
initiated (pulsing whistle tone).
?? Should the electronic control detect any failure,
an acoustic signal will sound (pulsing
whistle tone) for 30 seconds (only with AES
models). It is repeated every hour, if the fai
lure is not resolved. At the same time the
display starts flashing (for trouble-shooting,
please refer to section 4.13).
4. For a problem like this you usually disconnect the Temp Thermister which will cause the refer to run full time. Then see if it stops cooling in your parameters problem. IF so, then replace the Thermister.
5. Does your model have the optional rear cooling fan? Not ALL of this model will have the rear cooling fan. If you have the fan, then your fan Tstat may be defective. Doug

Doug, I do not see any flashing LED's when the fridge (AES model) is not cooling. The first couple of times that this happened, I did hear a beeping sound that was the same as the beeping sound when the door is not closed completely but no beeping the last few times it happened.

4. Disconnecting the temp thermistor is an excellent suggestion and one I can easily try the next time it happens.

5. I do have the rear cooling fan but it seems to work fine and runs when the fridge is not cooling properly.

Thanks for the suggestion.

Mike

[YC_1]

Turn the gas off and then remove the small orifice on the end of the propane tube that supplies the gas to the burner. Soak it in alcohol. DO NOT USE anything else such as a tooth pick or needle. Could be a tiny spec of anything acting like a check valve. Can be intermittent as heck.

Do not turn anything on with the end of the orifice off or you will find out how volatile 2 seconds of propane is. Cleared the dust out of my tree I can tell you for a fact.

[dougrainer]

1. Temp rise on your model will not cause any indication or beeping.
2. IF there is a failure, you will get a flashing LED stating what has failed
3. Should the door be kept open for too long
(more than 2 minutes), the blue external
LED starts flashing until the door is closed.
Only with AES models an acoustic signal is
initiated (pulsing whistle tone).
?? Should the electronic control detect any failure,
an acoustic signal will sound (pulsing
whistle tone) for 30 seconds (only with AES
models). It is repeated every hour, if the fai
lure is not resolved. At the same time the
display starts flashing (for trouble-shooting,
please refer to section 4.13).
4. For a problem like this you usually disconnect the Temp Thermister which will cause the refer to run full time. Then see if it stops cooling in your parameters problem. IF so, then replace the Thermister.
5. Does your model have the optional rear cooling fan? Not ALL of this model will have the rear cooling fan. If you have the fan, then your fan Tstat may be defective. Doug

[mondmn70]

The fridge is not in a slide and this occasional problem occurs even when the ambient temperature is in the 40'5 and 50's and does not happen even when the ambient temperature is in the 70's or 80's. I have also used an IR thermometer to measure the temperature on the fridge condenser and when it is not working the temp of the condenser drops from about 140 F to about 120 F

[beemerphile1]

Is it in a slide?

Most common problem for a warm refrigerator is poor air flow (convection) in the rear.

[dougrainer]

rockhillmanor wrote:
Check your converter and coach batteries first. The fridge needs good constant 12 volt for the thermostat to work irregardless of what mode you are using.

My fridge would come on and you think it was working but then later on it would not cool.

What happens is the fridge reaches the temp set and shuts off like it should. Only thing is if there is a 12volt problem the thermostat won't work and the fridge can't come back on. Fools a lot of dealership repair shops. Doesn't get past a good mobile RV repair guy though.

Mine was low 12 volt from bad converter that actually was boiling my batteries. Henceforth my AC and fridge would come on but couldn't come 'back on' when the thermostat called for it. Dealership just wanted to replace both.:S Mobile Repair guy said otherwise.

Was a big learning experience for me how things work in an RV and how to always call a Mobile RV repair man! :B

How much did the Dealership Service dept charge you for their diagnosis and why did you not have them do the repair? Doug

[mondmn70]

I keep a volt meter on the 12V system and it always showed between 12.3 and 12.7 volts during the episodes when the fridge was not cooling. The fridge would stop working but then resume working within an hour or so without any change in the 12 volt system.

[rockhillmanor]

Check your converter and coach batteries first. The fridge needs good constant 12 volt for the thermostat to work irregardless of what mode you are using.

My fridge would come on and you think it was working but then later on it would not cool.

What happens is the fridge reaches the temp set and shuts off like it should. Only thing is if there is a 12volt problem the thermostat won't work and the fridge can't come back on. Fools a lot of dealership repair shops. Doesn't get past a good mobile RV repair guy though.

Mine was low 12 volt from bad converter that actually was boiling my batteries. Henceforth my AC and fridge would come on but couldn't come 'back on' when the thermostat called for it. Dealership just wanted to replace both.:S Mobile Repair guy said otherwise.

Was a big learning experience for me how things work in an RV and how to always call a Mobile RV repair man! :B