Hi all,2008 WW CR3705 with the Dometic RM3862 fridge. I have been balls deep into this fridge several times. The first was the ciruit board. I bought one from dinosaur electronics and it worked well for a year. The same board had an ignitor issue and the board was warrantied. Long story short this current board is the third in a series of "warranty" boards.So I plugged my trailer in on Tuesday (flat ground). The freezer and fridge are perfect by the 24 hr mark. Come Friday I went to load a bag of ice into the freezer and the thing was warmer than it should be. I checked all lights, fuses and it was all in check. No "CHECK" light on.....nothing.Needless to say I transferred over to propane (bled the lines and all was good...fridge burner/pilot on). I got to my destination and it was 68*I am so sick and tired of this unpredictable fridge and/or the dinosaur board. I am going to get into to it tomorrow and check the obvious but at this point I am at a loss.Any ideas on what might be the issue?Is the fridge done?Thank youJoe

The way you describe it is like the 12V battery voltage is low. You need to check the voltage at the converter output, and at the battery when plugged in. Your charge voltage may not be reaching the battery, and then when the battery goes low, the fridge shuts down.It might not be the problem, but it's worth checking your battery voltage to see, and it's the source of a lot of problems that don't look like a bad connection.My fridge was not faulting, but the idiot light dropped to one bar out of four while I was plugged in, and I found a loose negative connection at the converter. I wiggled the wire, and the inside lights all jumped up in brightness. Tightened the connection, and all was well.

Most likely not the problem......but thank you for the helpIn AC and LPG mode the fridge lights are on, the burner is on in LP mode and still no cooling.Artum Snowbird wrote:The way you describe it is like the 12V battery voltage is low. You need to check the voltage at the converter output, and at the battery when plugged in. Your charge voltage may not be reaching the battery, and then when the battery goes low, the fridge shuts down.It might not be the problem, but it's worth checking your battery voltage to see, and it's the source of a lot of problems that don't look like a bad connection.My fridge was not faulting, but the idiot light dropped to one bar out of four while I was plugged in, and I found a loose negative connection at the converter. I wiggled the wire, and the inside lights all jumped up in brightness. Tightened the connection, and all was well.

CHECK light only comes on IF propane FAILS to light off....nothing to do with AC operationNo pilot flame..........only a main flame when propane lights.Thermostat controls heating cycle (flame or electric element on/off)Low Ambient Temp (LAT) Switch.............make sure it is OFF (when on keeps interior light on causing excessive heat)What/how are you measuring temps?What temp setting.......max (5)?Test for circuit board or cooling unitElectric element leads -----unplug them from circuit board and plug them DIRECTLY into the 120V AC outletRun for 24 hrsThis bypasses board......If fridge cools down freezer should be 0*F and food section should be 32*F or lower ---circuit board badIf circuit board bad (AGAIN) then you need to check your DC System for amount of AC Ripple (Dirty DC).AC Ripple is result of converter capacitors failing allowing AC Voltage onto DC SystemTo Test for AC Ripple.....just like testing DC Voltage except multimeter set to AC Voltage and then you take a reading on DC Circuit....can be done at converter or right at fridge DC terminalOver 1 volt AC can cause circuit board failuresIf fridge does not cool down (freezer might but food section doesn't) then cooling unit is blocked

Old-Biscuit wrote:CHECK light only comes on IF propane FAILS to light off....nothing to do with AC operationNo pilot flame..........only a main flame when propane lights.Thermostat controls heating cycle (flame or electric element on/off)Low Ambient Temp (LAT) Switch.............make sure it is OFF (when on keeps interior light on causing excessive heat)-No bulb in the fridgeWhat/how are you measuring temps? thermometer normally but this time I used a remote probe with a t/stat outside the fridge. I can tell you it was nowhere near how cold it is when workingWhat temp setting.......max (5)? Yes, I never change the tempTest for circuit board or cooling unitElectric element leads -----unplug them from circuit board and plug them DIRECTLY into the 120V AC outletRun for 24 hrsThis bypasses board......If fridge cools down freezer should be 0*F and food section should be 32*F or lower ---circuit board badIf circuit board bad (AGAIN) then you need to check your DC System for amount of AC Ripple (Dirty DC).AC Ripple is result of converter capacitors failing allowing AC Voltage onto DC SystemTo Test for AC Ripple.....just like testing DC Voltage except multimeter set to AC Voltage and then you take a reading on DC Circuit....can be done at converter or right at fridge DC terminalOver 1 volt AC can cause circuit board failuresIf fridge does not cool down (freeze might but food section doesn't) then cooling unit is blockedBoth freezer and fridge were equal temps by the time I got to my camp area. I just turned it off and decided not to think about itI will check all this tomorrow....thank you

Does it have assist fan or fans in the back outside of the fridge to move air? If they burn out it can breathe and while freezer will be cold the fridge will not. Just a thought.

Fridge WOES......Again | Good Sam Community

joe_blow
Explorer
Aug 23, 2016
YC 1 wrote:
Is it in a slide?

Is the drain tube cracked?

Has the drain tube been moved?

Not in a slide

If you are referring to the water drain tube it has not been moved and I'll go look to see if it is cracked.
mudmaker
Explorer
Aug 24, 2016
If there is a fan it should be attached to a thermostat on the cooling fins directing the fan to come on at 130 degrees or at least around there. If it's not then the heat can't rise and escape so the freezer will work but not the fridge. Thermistor should read between 8-10000 ohms after about ten minutes in the ice. To make sure the board works just unplug the the thermistor from the circuit board and over about a day at most the fridge should become a freezer. That will prove the circuit board is functioning.
Just went through this on my parents fridge last month. These instruction were in the dometic book and online for troubleshooting. There are checks for the heating elements but I never got that far. Replaced the fan with two, (the factory bracket will accommodate two in my parents) and works really good now.
Oh and double check the door gaskets too. Unbelievable how much cold air you lose when the door opens.
joe_blow
Explorer
Aug 24, 2016
Well after diagnosing for most of the day it appears that my cooling coils are the issue. I contacted this company http://www.arcticoldstore.com/dometic-rm3862-brand-new-manufactured-cooling-units/ and the guy was really helpful. In a nutshell the fridge had two ways to heat the ammonia and neither was doing anything. I pulled the fridge out today and didn't notice any major yellowing indicative of a leak but the tech said that at times the coils get plugged.

After describing all the diagnostics/findings I went through and explaining what symptoms I am experiencing the guy stopped me mid sentence and guaranteed to me the coils are the issue. Pretty bold statement but he knew quite a bit about the fridges and their operation so I am going with it.

I will post once I install the new coil assembly. Looks like a really nice self contained, fully enclosed unit. Not to mention it has a lifetime warranty to boot.

Thank you for the help

Joe
joe_blow
Explorer
Aug 24, 2016
Thank you for the advice. I had plans to add two fans since it was out for preventative maintenance purposes. You mentioned the thermistor. I was considering buying one of these http://www.ebay.com/itm/Dometic-Thermistor-3851059042-RM3662-63-2852-62-3862-3-/282094933120?hash=item41ae2b1480:m:mWCilCxvy5zJZbuaEnKHpAQ&vxp=mtr

Any feedback on this unit?

thanks

mudmaker wrote:
If there is a fan it should be attached to a thermostat on the cooling fins directing the fan to come on at 130 degrees or at least around there. If it's not then the heat can't rise and escape so the freezer will work but not the fridge. Thermistor should read between 8-10000 ohms after about ten minutes in the ice. To make sure the board works just unplug the the thermistor from the circuit board and over about a day at most the fridge should become a freezer. That will prove the circuit board is functioning.
Just went through this on my parents fridge last month. These instruction were in the dometic book and online for troubleshooting. There are checks for the heating elements but I never got that far. Replaced the fan with two, (the factory bracket will accommodate two in my parents) and works really good now.
Oh and double check the door gaskets too. Unbelievable how much cold air you lose when the door opens.
Old-Biscuit
Explorer III
Aug 24, 2016
Guess you didn't pull electric heat element leads off of circuit board and plug the ends directly into 120V AC outlet like I suggested?

Running element directly bypasses the board and would determine if cooling unit worked or not..........

Hope it wasn't just the thermistor, the board or even poor ventilation/air flow :H

Didn't test for AC Ripple either.......
Multimeter set to AC Voltage but leads connected to 12V DC connection
joe_blow
Explorer
Aug 24, 2016
Old-Biscuit wrote:
Guess you didn't pull electric heat element leads off of circuit board and plug the ends directly into 120V AC outlet like I suggested? I have not purchased any thing yet. This test is tomorrow morning.

Running element directly bypasses the board and would determine if cooling unit worked or not..........Correct.....tomorrow

Hope it wasn't just the thermistor, the board or even poor ventilation/air flow :H

I tested ohms on the thermistor and it was within ranges, I went through the board with the help of the dinosaur electronics tech and it appears to be working....as far as airflow I highly doubt it since nothing has changed and everything is pretty clean and clear in there

Didn't test for AC Ripple either.......
Multimeter set to AC Voltage but leads connected to 12V DC connection

This didn't yield any results for me. I tried it a few times and it never gave me anything near a readable value. Which leads me to my question.

My inverter has two pieces of romex coming from the output side. Where in the trailer is my fridge tied into the inverter? I have never run the inverter to use my fridge while dry camping just to watch TV....that's it. I am still trying to grasp how the inverter ties into the fridge operation on the 12V side.

I have constant battery voltage at the fridge distribution block....nothing less or more.

Thanks
Joe
Old-Biscuit
Explorer III
Aug 24, 2016
Inverter supplies 120V AC...it is a draw off batteries

Do you not have a converter?

If batteries only supply DC System then you will not have issue with AC Ripple.
AC Ripple is a result of Converter using 120V AC to supply DC

No converter.....no AC Ripple

Only mentioned AC Ripple due to the number of circuit boards you have changed out.
joe_blow
Explorer
Aug 24, 2016
Old-Biscuit wrote:
Inverter supplies 120V AC...it is a draw off batteries

Do you not have a converter?

If batteries only supply DC System then you will not have issue with AC Ripple.
AC Ripple is a result of Converter using 120V AC to supply DC

No converter.....no AC Ripple

Only mentioned AC Ripple due to the number of circuit boards you have changed out.

The boards were a problem on their end. They told me they had a bad batch. The current one is the newest format and programming.

No sir....I have a xantrex freedom 458 inverter/charger that controls two outlets in the trailer and charges the house 12V DC and gives me 110V from 12V DC to power some items in the trailer when the ONAN 5500 is not running

I am in the process of isolating the coils. So far the heating element is hot as hades and the heat stops right at the top of the coils before the condenser.....will go no further. It has been 3 hours so far. Not a hint of temp change in the freezer or fridge. By this time I would have felt a temp change in the freezer given past performance

I did confirm the 60 cfm fan and therm switch work. I am going to install one 200cfm fan instead of two 60cfm fans since the room is limited and I don't want it melting next to the flue.

Old biscuit....questions for you sir.

Any ideas on the:

-thermistor modification I posted earlier in the thread? I tested the thermistor and it is within Ohms range but its out on the floor why not change it or modify it. What are your thoughts on the mod? http://www.snip-the-tip.com/cgi-bin/articca.cgi

-where I can get a new two prong therm heat switch for the fan (its way up there and I'd rather change it now that its out and in my garage.)

Thank you very much for the help!

Joe
Old-Biscuit
Explorer III
Aug 24, 2016
Snip the tip thermistor is a good option when one needs to replace faulty OEM thermistor and not wanting to run leads down to board.
But if fridge out..OEM thermistor is better

Dometic fan/t-stat install

Fan thermostat switch
htwheelz67
Explorer
Aug 24, 2016
I have the same fridge, no problems yet but after reading this and other threads like it I'm swapping in a residential fridge.

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