Adjust Thermocouple Position?

[shaunr68]

Hi all, having a few problems with the fridge in my van, grateful for any advice please.

The fridge is a Norcold badged Thetford unit, I believe an N80. It works fine on mains and 12v. The problem is with the gas system.

The previous owner only ever visited campsites with EHU so the fridge hadn't been run on gas for years. At first the fridge didn't ignite at all so I have cleaned the burner unit, cleared a blockage in the gas jet with compressed air and replaced the spark generator. It now lights on gas and burns with a healthy blue flame, but won't stay lit. As soon as you release the gas knob the flame goes out.

The symptoms would suggest a faulty thermocouple so one new thermocouple later and it does exactly the same thing.

This is the thermocouple. There are two different types, this is the earlier V1 model.



One thing I've noticed is that the tip of the thermocouple does not sit directly in the flame. It is set back a bit, but does not appear to be adjustable. The arrangement looks very like this one from a Dometic fridge. As you can see the spark electrode is at the front, burner in the middle and the thermocouple is at the back. I can't see any means of adjusting the thermocouple other than bending it forwards so that it sits further into the flame, but such a clunky means of adjustment doesn't sound right to me. On the other hand I did manage to get the fridge to run a few times when on a slight slope and my theory is that the slope meant the thermocouple was now sitting in the flame.



I think what I'll do tomorrow is put the old thermocouple back in and try bending it, nothing to lose if it breaks.

Failing that would you say the gas valve is at fault? I hope not as it looks like a discontinued part - thetford 623027 just in case anyone has one knocking about in their shed!



Many thanks

 

[n brown]

you sound fairly handy
with gas off of course , you can test a t/couple [tc]
where the tc goes into the valve it has a small nut screwed into a large nut . undo the small one to release the tc
now undo the large nut and remove the solenoid valve
holding the end of the tc against the depression in the end of the solenoid, hold the other end of the tc in aflame , gas hob will do . now get someone to push the spring loaded diaphragm against the solenoid. if the tc works , it'll stay there till you take the tc out of the flame , after a few seconds it'll spring away
once you know for sure that it works you just need to get it into the flame enough for it to operate

 

[spigot]

The thermocouple tip should be well into the flame. Move it till it is. If you need a new one, buy a "super universal" one from Screwfix or Toolstation. They come with a plethora of fittings for very little money

This “Super Universal” thermocouple has given me “food for thought”, getting slightly off the fridge subject.

The Flame Failure Device on the oven at home has packed up, a new unit costs over £100. The faulty part is the thermocouple that leads to the flame & at under a tenner I think it’s worth a try.

Anyone with thoughts on this?

 

[n brown]

This “Super Universal” thermocouple has given me “food for thought”, getting slightly off the fridge subject.

The Flame Failure Device on the oven at home has packed up, a new unit costs over £100. The faulty part is the thermocouple that leads to the flame & at under a tenner I think it’s worth a try.

Anyone with thoughts on this?

should be fine , and if you get it from Band Q you can always return if there's a problem. a thermocouple is a thermocouple , so no problem there , it's just whether you can fit it on your oven

 

[undertaker]

Hi, I’m no expert but my fridge had the same symptoms as ops fridge. I too suspected that the thermocouple wasn’t close enough to the flame. I couldn’t see any way of getting it closer so decided to replace it. Whilst waiting for replacement I decided to clean the tip of the original with a bit of fine emery paper. Worked a treat that was over 12 months ago and the replacement is still in a drawer. As op says previous owner hadn’t used gas perhaps it’s just a bit dull on the tip. Good luck with it anyway.

 

[shaunr68]

Thanks all. I have tested both the original thermocouple and the replacement and am confident that they are both in working order. The positioning is slightly off centre, meaning the thermocouple tip sits about 5mm back from the centre of the flame. There is no way of adjusting this so I removed the little bracket that holds it in place and rested the thermocouple so the tip was dead in the centre right above the burner. No change, the fridge will ignite but as soon as I release the gas knob (even if held in for a minute and withdrawn very slowly) the flame goes out.

Another thing I've noticed is that it will not ignite at all unless the gas control knob is turned right up to max.

Am I right in thinking that the gas valve is the likely culprit? As I said the earlier version is discontinued but I did manage to find a supplier in Spain with it in stock.

Gas valve Thetford Fridges - older models | Thetford N112 Fridge Spare Parts | Leisureshopdirect

https://www.ckapri.es/epages/63894172.sf/en_GB/?ObjectPath=/Shops/63894172/Products/04R623027

 

[jagmanx]

We had similar

Thanks all. I have tested both the original thermocouple and the replacement and am confident that they are both in working order. The positioning is slightly off centre, meaning the thermocouple tip sits about 5mm back from the centre of the flame. There is no way of adjusting this so I removed the little bracket that holds it in place and rested the thermocouple so the tip was dead in the centre right above the burner. No change, the fridge will ignite but as soon as I withdraw the gas knob (even if held in for a minute and withdrawn very slowly) the flame goes out.

Another thing I've noticed is that it will not ignite at all unless the gas control knob is turned right up to max.

Am I right in thinking that the gas valve is the likely culprit? As I said earlier the earlier version is discontinued but I did manage to find a supplier in Spain with it in stock.

Gas valve Thetford Fridges - older models | Thetford N112 Fridge Spare Parts | Leisureshopdirect

https://www.ckapri.es/epages/63894172.sf/en_GB/?ObjectPath=/Shops/63894172/Products/04R623027

Albeit on a Dometic unit ........sparking but no gas lighting so no gas getting past the said valve (below)

It turned out to be the gas control valve was not working even though the peripheral components were OK
So New gas control valve and all is well (except the wallet)

 

[shaunr68]

Thanks all. I have now sourced and fitted a second hand gas valve and the fridge will STILL not stay lit when I withdraw my finger from the gas knob, even after holding it in for ages.

What next - selector switch? This fridge will end up like Trigger's broomstick!

 

[Nabsim]

The next step is to find out what is wrong instead of replacing bits one by one

I am sure that what the OP wants to do and is in need of instruction

 

[shaunr68]

Thanks all, true I did assume that the brand new replacement thermocouple would be in working order. However I'm not so sure now.

I have now tested both the old and the new thermocouples using the method suggested by nbrown in post #2.

In both cases, with the tip of the tc held in a flame and the other end pushing agains the solenoid, when the spring is depressed it immediately springs back out again. It does not stay depressed.

So this means both my original and brand new replacement tc were both faulty?

 

[Channa]

Unlikely two fsd and two gcv are faulty

1) check the knob when depressed is opening the gcv correctly and upon release remove to do this the splines stick and female parts wear requiring packing
2) if all seems OK check all connections on the fsd and what it mounts too Akin to a bad earth a common problem on Glen appliances
Also adjusting using locknuts as described earlier, the fsd tip should be in the tip of the flame ideal position

Channa

 

[shaunr68]

Thanks all.

Another new thermocouple and the fridge now lights! Yipee! So it seems my original thermocouple had failed and the brand new replacement was faulty. The fridge is still very cranky to light on gas, you have to hold the knob in for a good 30 seconds and withdraw it very slowly, but at least it does light now. I'm off on a 6 month continental trip on Monday so it's very good timing. Thanks fellas, appreciate the expert input.

 

[jagmanx]

Fridges on gas

Our dometic fridge was not cooling.
Burner. Faulty...Replaced and all ok for 2 months.
1st gas tank mt.
Change to 2nd tank.
Lots of sparking but no burner.
Diagnosed as faulty gas valve.
Replaced and all is fine.

My thanks to
1 a Dometic moho repairer near Napoli
2 similar near Trier.

Fridge 12 years old.
A full 5 month tour for the last 5 years.
Fridge on gas nearly every night.
No complaints...