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Randall
Randall, RVIA Certification
Category: RV
Satisfied Customers: 10334
Experience:  RVDA/RVIA Master Certified Technician with many years experience.
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I have a dometic refer- Model RM3862 / S N 90801583 . When

Customer Question

I have a dometic refer- Model RM3862 / S N 90801583 . When it automatically switches from AC to Gas it will fire but will shit down . The AC function works fin . I have replaced the control board. It did not change the problem. I can bypass the controls to the burner and make it work . Have any suggestions?
Submitted: 6 months ago.
Category: RV
Expert:  Randall replied 6 months ago.

When you say "bypass the controls to the burner" here.........what are you doing exactly? This sounds like the thermocouple is bad. You can test that with a Bunsen torch and multimeter that reads in millivolts. You would need to see at least 18 millivolts to be good, but over 20 is better. It also might be a bad ignition module. I am attaching a copy of the Dometic Manual which covers this model for you. See that section. Print out a copy so you have it. Hope this proves helpful here. Please get back to me if you need more help with the testing or we need to dig deeper into this if those items test out good. All follow up Q&A are included in the question fee. http://bryantrv.com/docs2/docs/domser.pdf

Expert:  Randall replied 6 months ago.

They made quite a few versions of this, so if you need parts I need to know the Product Number off the data tag. Thanks!

Expert:  Randall replied 6 months ago.

Just checking back in to see if you were able to resolve this or do you still need some additional input from me here?

Customer: replied 6 months ago.
Ok , I replaced the thermocouple , no change . I can turn off the power button and turn it back on it will hesitate for about 15 seconds . Then the burner will light and stay lite for about 5 seconds and then shut down . The check light comes on the panel . I can repeat same sequence and same results . I know it is not the gas or air in the system because I could make the burner work by bypassing the control . My thoughts are that the burner is not running long enough to heat up thermocouple to generate the current to the control to keep it running .???
Expert:  Randall replied 6 months ago.

If the flame is not hot enough the thermocouple won't generate full millivolts and the board will shut off the gas valve. IF you haven't checked the LP pressure that would be good to do. If that is good and the flame is "dancing" on the burner which means that it is waving and emits a "dull roar" that you can hear, then that should be fine. A soft blue flame isn't good or one with orange in the edges. If the pressure is good, there may be debris in the jet or in the inlet of the gas valve from construction debris. You can wash the jet in solvent and blow dry with your mouth only. Too much pressure can damage it. You also might want to have the control board tested to be sure that the flame sense isn't bad. Most shops have a board tested and can do this for you. Those are the next steps to try here.

Expert:  Randall replied 5 months ago.

Just checking back in to see if you may have missed my response to your question a few days ago? If you still need some assistance and input from me here, please get back to me. Thanks!