Fridge not working on gas, works fine on AC

[Boatycall]

Hi all,
First off, I'm asking for a friend. We were camping a couple weeks ago, and he mentioned his fridge won't run on gas. Being pretty decent at troubleshooting I offered to take look.

Here's the details--
* Very new toyhauler, 2014 Raptor. Yes it's under warranty, but the dealer says it's going to be 4-6 weeks for his turn in line.
* 12CuFt Dometic side by side fridge
* AC, works fine.
* Gas - goes through the normal lighting sequence, igniter pops, gas valve opens, main burner DOES light. 5 or so seconds later, it intentionally shuts itself off.

My suspect is the thermocouple that detects and sends the "it's lit" signal back to the board. It is in a spot where it cannot be moved, nor does it look like it has moved away from where it's supposed to be.

Here's what I don't know - I do know what a thermocouple does, creates a very minute voltage when heated. My question for testing it - what voltage should I see on a VOM open-circuit(disconnected from the board, hooked directly to the meter)?

Also - the thermocouple isn't directly connected to the main board, it goes through a very small black box with a red LED on it. That LED goes red when the thermo couple is disconnected, so it's some sort of continuity check. That little black box is then connected to the main board. What is that little black box?

And just to reiterate, this is all the info I have for now, it's not my RV. Any help is appreciated, Thanx!

[Chris_Bryant]

We really need a model number (and product number for Dometic refrigerators). That doesn't sound familiar- the NDA side by side did have a different ignition control, but no thermocouple. Some RM1350 models do use a thermocouple, but it goes directly to the main board.

To be honest- a box with an LED sounds like the recall boxes on Norcold 4 door models.

[Boatycall]

enblethen wrote:
No thermal couple. Should have a flame sensor.
I would check to make sure the probe is directly in the flame.
This should help.
Dometic service manual from Bryant RV

THANK YOU very much!! That had exactly what I needed. For reference in case anyone needs this same info later, here's what the service manual said--

To check the flame sense circuit of the lower circuit board, operate the refrigerator on GAS and measure the millivolts between J4 (NEGATIVE) terminal and J10 (POSITIVE) connection from the thermocouple. The thermocouple should produce 20 millivolts DC minimum.

Anything less than 20 millivolts will cause erratic gas operation. The meter should read between 25 to 35 millivolts with the gas flame burning.

[enblethen]

No thermal couple. Should have a flame sensor.
I would check to make sure the probe is directly in the flame.
This should help.
Dometic service manual from Bryant RV