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3Way Fridge Gas Ignition Issue


geffers
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Re Dometic RM 6401

Question. When the burner lights and the gas valve stays open maintaining the flame what causes the ignition spark to cease?

 

In the past the ignition light & clicking would stop.

I've struggled several times with not working on gas and partially removed the fridge several times but this problem is new .

I have attached a diagram of the control circuit when on gas.

The connections to the gas valve has gas in and out, the thermocouple and a pair of wires to/from the control switch.

These are open circuit when the control switch is NOT in the gas position. I guess this is to prevent the gas being fed to the burner when in other modes.

What I cannot work out is the mechanism that stops the ignition when the flame is lit. The diagram does not appear to show this process.

 

Any light thrown on this gratefully received.

PS Could not find the way to attach the diagram .

 

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Presumably the igniter circuit senses an output from the thermocouple &  ceases?

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At present the thermocouple holds the gas valve open once the flame is established but the ignition continues. There is no obviously connection to the igniter

 

A renewed look at the gas control valve.
There are 4 connections.
1. Gas in
2. Gas out.
3. Thermocouple.
4. 2 terminals, connected to energy type selector switch.

These terminals at present (fridge out, and disconnected) are internally shorted together, I assume because the gas valve is closed and no way should it open in other modes.
The selector switch provides an external short to these terminals except when gas is selected.
There is an attachment (thermostat) to the gas valve assembly which I think is connected to the temperature control which has no function when the fridge is on gas.
In other words, I fail to see how the ignited knows when to stop.

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The problem is fixed!

Success it works! You never stop learning, all down to spark rectification.*  Before ordering a new igniter generator I did a few checks following information gleaned suggesting that poor connections in the region of the ignitercould be the cause .

Supplementary earth appied to burner, 3 pin socket on igniter reseated several times, all to no effect.

Re-inserted, several times, the electrode wire into the igniter,  Bingo ignition, light operates as it should.

Conclusion. Poor igniter lead connection to spark generator.

 

*I have learnt that spark rectification provides a means of the igniter gerator being able to detect a flame via the current being passed down the spark electrode.

 

 

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 Well done geffers and :Thankyou: for coming back with the solution.

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Indeed, well done geffers! Now there's something I've never heard of: spark rectification!

Another nugget of info  to file away for possible future use!

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