Dometic RM 3862 quit working in LP gas mode....

[mikeylikesit]

Works fine in AC mode. Fires and runs for 30 seconds or so and trips off, with the "check" light illuminated. I can reset it and if fires again but trips off.......
same symptoms whether plugged into shore power or not....

so, when it fires it has a good blue flame, and my voltages are good. the thermocouple was quite dirty so I used a tiny wire brush on that, no change.

after reading a bunch of older threads, I'll try cleaning the terminal connections at the control board, but I've unplugged and replugged the t/couple wires a few times so I don't think that is the problem......

I did test the t/couple for resistance, it's open until it gets warm (10 seconds or so upon start up) then ohms climb pretty fast......should I be checking for millivolts instead?

I guess I'll start with a new thermocouple.........it's the least expensive part. I've located a control board so I will get that if the new t/couple doesn't fix it.

am I missing something simple?

thanks in advance for any suggestions!

 

[Rene T]

Do all your stove burners burn OK all at once? Lite all of them to eliminate a gas flow problem.

 

[mikeylikesit]

stove works fine. I can watch the fridge burner and its got good flame until "something" trips it off.
thanks

 

[DonTom]

I guess I'll start with a new thermocouple.

I expect that is your problem. That is where I would start as well.

-Don- Reno, NV

 

[Gary RV_Wizard]

By thermocouple, do you mean the igniter/flame sensor at the burner or the thermister inside the fridge? The thermister thermocouple signals the interior temperature to the controller. THAT thermocouple is obviously working because the burner tries to ignite and AC mode works too. If your 3862 has separate igniter and thermocouple sensors, you can try replacing just the thermocouple. Otherwise, its the combined part. Also verify that the separate flame sensor thermocouple is in the flame area and not caked with an insect next or rust flakes.

If the igniter/sensor can't get a "flame sensed" signal back to the controller, the controller will quickly shut off the gas. A corroded wire connection for the flame sensor is a fairly common problem.

 

[mikeylikesit]

its the flame sensing thermocouple Gary, I'll go back and double check the connections for corrosion. Thank you!
(RV store did not get a parts delivery today dang-it! Now have to wait till tomorrow )

 

[mikeylikesit]

so, it ended up being the thermocouple. I did test it, it produced 21mv when heated with a lighter but it took a looooong time to come up. Not sure how those "wear out", but the new one, when tested the same way, came up to 26mv in about one fourth the time. Figure the control board probably goes into a timing sequence and the old T/couple didn't meet spec soon enough.

Thanks All!

 

[Gary RV_Wizard]

Glad it turned out to be an easy fix. Thanks for letting us know the final solution.