How do you test the fridge thermocouple?

[XRN]

Fridge is an Electrolux RM6401L. Currently I have the fridge out on the floor of the van to check electrics after the gas was cutting out. I have access to the burner thermocouple and the thermocouple connection to the gas valve on the top and I want to check the function of the burner thermocouple before refitting the fridge. I have removed the 2 black wires from the white bit of the gas valve which go to the selector switch, and then measured resistance across the 2 exposed terminals on the valve which is about 0.4 ohms at ambient. Using a cooker hob ignition torch I heated up the thermocouple and watched the resistance increase to about 17 Ohms, then back to 0.4 Ohms when heat was removed. Whilst this shows the thermocouple is detecting heat I am confused as to how this works to cut off the gas when the flame goes out. I would have thought that it would have gone open circuit when heat was removed to shut the gas so can anyone with knowledge of this type of control say whether I am testing correctly and are the results what I should be seeing?
Thanks in anticipation

 

[andy63]

when the thermocouple is heated it generates a small voltage which can be checked using a mv scale on a decent meter.. from memory the ones I've checked (by attaching the leads of the meter to the removed usually threaded end of the thermocouple.. its easy enough to identify the two different metals at that end..) it should generate something in the order of 30 something to low 40 odd millivolts.. as soon as its in a flame..
the contact of that threaded end is important when its screwed home.
Andy

 

[XRN]

andy63 Thanks for that info, I haven't removed the thermocouple at the spanner end, does this check need to be done whilst removed or can you measure the millivolts on the electrical terminals?

 

[andy63]

andy63 Thanks for that info, I haven't removed the thermocouple at the spanner end, does this check need to be done whilst removed or can you measure the millivolts on the electrical terminals?

you have to remove the thermocouple to check that voltage and have a meter with a mv scale...
I think that small voltage the couple generates is used to generate a small magnetic field which holds a contact enabling the gas valve to stay open... once the voltage is lost the contact opens and the gas valve shuts... it was a long time ago lol.... and I think the one I was working on was for a gas fire not a fridge but I imagine that are similar
Andy

 

[dave newell]

Use a thermocouple tester, plenty available on ebay.

D.

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[Wagoneer]

Suggest the OP checks the gas burner assembly for corrosion where the bracket for the support of the electrodes fit.

On mine the bracket acts as the earth return. The bracket clamps onto the gas feed pipe and this is where the corrosion was found. Once it had been cleaned up the ignition worked perfectly.

I suspect the corrosion was caused by water overflowing the plastic bowl which catches water from the fridge.

 

[Jev88]

Start the fridge on gas and you usually have to manually hold the valve open whilst the thermocouple warms up. Then let go. If flame goes out repeatedly even after holding manually open for 40 seconds or so then it is faulty.

 

[XRN]

Use a thermocouple tester, plenty available on ebay.

D.

Thermocouple tester ordered, thanks dave newell lvs I will also check the other items suggested.

 

[NigelDobboRob]

I have checked with a tester and works fine, but when you let the button out it still goes out
.

 

[KUSKUS]

Old thread .

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[Richard n Ann]

I have checked with a tester and works fine, but when you let the button out it still goes out
.

Is it in the flame properly?

 

[Richard n Ann]