Dometic RM2852 Refrigerator

[CA Harts]

I have the above in MH. Works great on Shore power or when running generator. Will not work properly on D.C. The electrode provides a spark, gas valve opens and burner lights. Burner is clean. The problem is the spark never stops. I checked the voltage going across the Thermocouple and it increased up to 35mv like in Dometic service manual. The D.C. Voltage is right at 14.5v (MH plug into shore power). Checked grounds and have less then 1 ohm across all ground connections. I have unplugged the AC power to control board and also set for gas operation only. Same result. Ideas ?

Thanks

[BFlinn181]

Not sure you have a thermocouple, many newer gas appliances don't. Instead, they sense flame through the electricity flowing between the electrodes in the ignitor. From pg 15 in the Dometic manual: "The igniter senses the flame thru the electrode
and communicates with the lower main control. The integrated
igniter used on certain Dometic model refrigerators
operates on 12 volt DC thru the control board. On gas
operation the igniter senses the resistance through the
flame between the electrode and burner. When there is no
flame at the burner, the resistance is high and the igniter
begins sparking to light the burner. As soon as the flame
is lit, the resistance between the electrode and burner
drops and the igniter stops sparking. The resistance is
monitored by the igniter, and, if for any reason the flame
goes out, the igniter begins sparking until the burner is lit.
This insures that the flame will always be lit when desired."

You might try gently wiping the electrodes to see if they've got soot or other dirt on them, keeping resistance high enough to continue sparking.

[CA Harts]

Thanks, I do have the older unit with the thermocouple. In the manual (page18 that I have) there is a diagram that shows the older unit with the thermocouple.

[12rvrepair]

Its ether the thermocouple or the relay isn't holding on the board or not sensing the flame. Most likely the board

[CA Harts]

Thanks. I'm thinking it probably the board, the thermocouple seems to be working correctly from what I can tell by the reading I get as it heat up. I'm going to remove the burner and make sure it clean and make sure all the power and grounds are good and tight.

[CA Harts]

Well cleaned the burner, thermocouple and the ground connections and seems to be forking fine for the last 4+ days.

Thanks to all have safe trips down the road and Happy New Year.