Gas oven thermostat

[Reentrant]

Our gas oven is about 20 years old and I've just had to replace the thermostat for the third time. The part is getting harder to find and is consequently way more expensive (around £100) than it used to be. Next time a new oven might be the better option.

Looking at thermostats for modern gas ovens (£35 or so) the copper tube and phial/sender all look pretty much the same as mine. Is it possible to change that - assuming that's what fails - rather than the whole thing which includes the gas tap assembly?

Maybe it would need calibrating somehow but I'm not sure if it's pre-pressurised. Guess I could take the old one apart but that may be why it's failed if it lost pressure ...

[Fredxxx]

I suspect the amount of valve movement is similar. Why not take your old one part and investigate? The fault might not be obvious.

You might find some old "new stock" on ebay in the mean time for next time!

[Graham.]

A couple of Ebay "saved searches" can work wonders for obscure items, given enough time. Use a separate search with just the part number.

That's how I got a replacement gas valve for my (then) thirty year old boiler. Fortunately it was hobbling along on its original valve so I could wait. It was the best part of a year until I got an email alert of one that wasn't a silly price.

[Brian Gaff]

I've often wondered how such things work. The ones with a coiled tube and a thicker end with a knob on one end and thethicker end in the oven always seem to be crude to me. I wonder why even modern ovens use this over the electronic alternative? Brian

[Fredxxx]

The sensing end could easily be a thermistor but the electronic side would have to endure a high temperature and you would need to drive a gas valve as well as needing power.

A simple bulb of liquid which when expands has sufficient force to hold off a valve seems incredibly simple and reliable to me.

Perhaps a thermopile? I have seen a gas fire use one in conjunction with a conventional thermostat to turn the gas valve on and off.

[Reentrant]

Maybe crude, but I tested the new thermostat using an IR thermometer. At gas mark 5 the oven temperature was right to within a couple of degrees (375F).