Dometic RM3862 fridge

Question

Hi guys,My refrigerator woes I cannot shake LOL. Quick synopsis:Swapped out complete coil unit from arctic cold 4 years ago and added auxiliary fans to the condenser (3). To date the fridge cools fantastic on 110v using the heat stick. Recently the fridge starting having issues when on propane.I called Dinosaur electronics to see if they could diagnose their board as being the issue. The tech had me do some tests and he advised to remove the gas valve, cycle it with 12v (magnet) and spray brake kleen incase their was cr*p in there and it was sticking. I did and it worked ok for a bit, but it stopped working all together that same day, one day into the tripFast forward to a complete new valve/burner/ignitor assembly installed today. Bled the line, fired up perfect and burned for about an hour and went out again. The fridge cycles through its on/off process and the burner comes on for 30 seconds and off for 30 seconds.....repeating.SO....with that said.Am I not understanding how this unit operates and it is fine or should the unit (like a water heater) stay lit until up to temp and cycle as needed? The fridge was hot when this test and valve replacement was done.At this point I am thinking possibly the thermal switch with the two red wires on the flue or the board is the issue again.I am kind of at a loss on this one....or I am just not understanding the propane operation.Can someone offer some advice please.ThanksJoe

old-biscuit · Answer

Thermal switch on stack TRIPS from overheating...NO Auto Reset
When tripped ALL DC is secured

Your model uses a spark electrode to provide ignition of gas AND a thermocouple to prove flame is lit
Bad thermocouple, bad connections etc...no flame signal so circuit board dumps DC to gas valve

Gas Valve solenoid resistance
Remove the connectors from the solenoid and measure the resistance across the terminals.
The proper reading would be 49 ohms with tolerance range of ten percent.

Thermocouple millivolt readings
To check the flame sense circuit of the lower circuit board, operate the refrigerator on GAS mode, then measure the millivolts between J3 terminal and the other wire connection from the thermocouple.
The millivolt meter should read between 25 to 35 millivolts with the gas flame burning.
Any reading below 18 millivolts could cause erratic gas operation.

Thermocouple
Dometic 2932052018
Lowest price I have seen

Service Manual

joe_blow · Answer

Thanks old biscuit.I saw that on line but where in the hell is this thing????I looked everywhere and see no traces of any wires or thermocouple. The only wires I see toward the heat source are two red into a small dime sized thermal switch on the exterior of the flue. According to the illustrations you provided, it is on the assembly I replaced. There is no such thing on my assembly.Perhaps I am missing something?Thank you

dougrainer · Answer

1. Jump the red wires to bypass the Thermal switch. That will tell you if it is a possible problem.
2. IF the LP fails to stay lit when called for, you WILL get a CHECK light.
3. If the refer is at or close to set interior temp, then leave the interior door open for 30 minutes to raise the Refer temp to continue testing.
4. YOU NEVER TAKE A GAS SOLENOID APART OR TAMPER WITH IT. PERIOD. TAKE IT LOOSE AND CHECK FOR OBSTRUCTION, BUT IF DEFECTIVE YOU REPLACE. NEVER ATTEMPT TO FIX or MODIFY. Dinosaur has some idiots working for them I guess. The Liability to tell someone to do what they did is tremendous.
5. Yes the refer LP cycles on and off as temp requirements are needed. Doug

joe_blow · Answer

Thanks for the advice. I will test it in a bit once I make it outside. The dinosaur rep did not tell me to take it apart, but merely CLEAN it by cycling the magnet and blowing through it.

I never start the fridge up initially using propane. The 110v heat stick is used to bring up to temp and the gas for travel and once I am at my destination if dry camping. With that said I am not 100% familiar with the burner operation cycles, and may be chasing my tail for nothing.

Hypothetically speaking: At initial startup (hot) using the LP function only, shouldn't the flame remain on for hours straight until the fridge is up to temp.....then cycle off as need?

This is my primary question. :)

Thanks for the time
Joe

dougrainer wrote:
1. Jump the red wires to bypass the Thermal switch. That will tell you if it is a possible problem.
2. IF the LP fails to stay lit when called for, you WILL get a CHECK light.
3. If the refer is at or close to set interior temp, then leave the interior door open for 30 minutes to raise the Refer temp to continue testing.
4. YOU NEVER TAKE A GAS SOLENOID APART OR TAMPER WITH IT. PERIOD. TAKE IT LOOSE AND CHECK FOR OBSTRUCTION, BUT IF DEFECTIVE YOU REPLACE. NEVER ATTEMPT TO FIX or MODIFY. Dinosaur has some idiots working for them I guess. The Liability to tell someone to do what they did is tremendous.
5. Yes the refer LP cycles on and off as temp requirements are needed. Doug

old-biscuit · Answer

This is the burner ASSEMBLY (burner tube with spark electrode and mounting bracket)
LARGE Hole in mounting bracket is where the Thermocouple is installed

Spark Electrode Wire plugs into end of electrode and goes to 'reigniter box' (s/b grey wire)

Thermocouple has 2 wires ----Black & Grey
Black...ground ---goes to J10 terminal on circuit board (far right side)
Grey ---DC millivolt ----goes to J3 terminal on circuit board (left side)

Your fridge was part of the RECALL....stack temp switch installed and 2 red wires (DC In/DC Out)
DC+ from terminal block to stack temp switch then back to circuit board J4 terminal. Switch Opens no DC to fridge (no functions, no lights, no display ---nothing)

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