Oven light on when not in use - thermostat?

[Custom45]

Hi
I have a Rangemaster 110 electric oven, the left hand oven red light is permanently on even when the oven is not turned on (it's been like this quite a long time).

After isolating & disconnecting from mains I tested the elements, getting a reading of around 50 on the multimeter, suggesting elements are ok?

I took front panel out and tested thermostat switch, getting a reading of around 0.09, is this normal? I'm assuming I tested it correctly. Attached a few pictures below.

The bottom of the thermostat switch unit is quite brown, possibly from burning out?? There was a dead spider attached to part of it.





Bottom is a bit brown/black and looks like a bit is broken off?



After disconnecting all wires I put multimeter on the two terminals circled in red...



Thanks,

 

[Bodgedbuild]

I have a Rangemaster 90, I presume similar for the left oven at least, it's brand new and the oven light can be switch on irrespective of the oven being switched on, does yours not just have a push button to switch the light on and off?

 

[Custom45]

Sorry I've edited my post as it was misleading... it's not the oven light as in internal light, I meant the red light on the front next to the on off dial. That's the one that's always on, even when not in use.

 

[Harry Bloomfield]

I would make a guess at there is enough power tracking via that switch, to illuminate the light if it's a neon.

 

[Custom45]

I would make a guess at there is enough power tracking via that switch, to illuminate the light if it's a neon.

What does that mean? That the switch is at fault?

 

[Harry Bloomfield]

Yes, my best guess based on the blackening I could see on the switch in the photo.

 

[Custom45]

Thanks. The switch still works fine, turns oven on/off etc if that makes a difference?

Any idea what could cause that kind of blackening? Anything to be concerned about?

 

[Harry Bloomfield]

Thanks. The switch still works fine, turns oven on/off etc if that makes a difference?

Any idea what could cause that kind of blackening? Anything to be concerned about?

You will appreciate it is difficult to be sure from a photo - The blackening will be due to old age/ lots of use/wear and tear in a heavily loaded component. Resistance in the contacts make them generate heat, the more heat the more they become damaged, generating even heat.

 

[Custom45]

Absolutely, I wouldn't expect anyone to diagnose fully without seeing it in person. Thanks for your help. I'll try and locate one of the switch units and replace it. I think you can buy them without thermostat attached for about £30.

 

[Bodgedbuild]

Absolutely, I wouldn't expect anyone to diagnose fully without seeing it in person. Thanks for your help. I'll try and locate one of the switch units and replace it. I think you can buy them without thermostat attached for about £30.

I could be wrong but I cant see how the thermostat and oven control could be separate? I thought the steel "wire" going from the sensor in the oven to the switch was actually a capillary tube and that they were all one unit?

Edit, I could be wrong on older models, mine had the tube pinched by a screw from new and had to be replaced.

 

[Custom45]

That's right. So you have the oven control switch unit, then attached to that is a small white module, attached to that is a thin wire that runs down into the oven cavity to a tube that detects temp.

On these the thermostat white module/wire can be detached from the switch unit, which is what I have now done in the photo below.

I'll order a new switch unit, reattach stat and hopefully it'll be ok. The switch is £26, the complete switch/thermostat assembly is £58. I swapped the stat over with the one in the right hand oven, it worked fine, so I think the stat is ok.