correct wiring for oven grill door microswitch?

[axisus]

Hi, I was wondering if anyone can help me, I'm trying to work out which two of these three microswitch tabs to use. I have a Hotpoint Hug52 oven and the grill won't stay lit. I checked the thermocouple and it looked in a poor state so I have installed a new one. I took a photo of the wires on this switch but like a dingbat I accidentally deleted it. Basically it has one wire coming from the thermocouple, and one from the front panel controls. The switch is operated by the oven door closing, as the door should not be shut when the grill is in operation. Thanks

 

[westward10]

Normally the bottom terminal is common, the end terminal closest to this is 'normally open' the other 'normally closed'. So one definitely goes to the bottom one then it is a question of whether it operates on normally closed or normally open. Can you see scratch marks on the brass spade terminals.

 

[axisus]

Thanks. I've tried all permutations now and it still doesn't work! I can't believe that a static switch like that can go wrong? I can't get to it well enough to remove it.

 

[DPG]

Thanks. I've tried all permutations now and it still doesn't work! I can't believe that a static switch like that can go wrong? I can't get to it well enough to remove it.

As long as you use the common terminal for one of the connections then there are only two possible permutations.

Are you sure the original switch was actually faulty? Do you have a multimeter?

 

[Avo Mk8]

Are you sure the problem is not with the thermocouple you replaced, eg the connector mating correctly?

This is a gas appliance and regulations apply - if you're changing a non-gas user serviceable part OK, but legally the manufacturer may consider this a job for a Gas-Safe registered engineer.

 

[brianmoooore]

This is a gas appliance and regulations apply - if you're changing a non-gas user serviceable part OK, but legally the manufacturer may consider this a job for a Gas-Safe registered engineer.

Totally legal to work on gas appliances in your own home if you are competent to do so.
In my experience, being qualified as a Gas Safe engineer is no guarantee of competence, the same as a sparky being a member of a scheme.

 

[Avo Mk8]

OK axisus
Following on from the above, since you've changed the thermocouple we'll assume you are competent.
As a test, connect the two microswitch leads together (without the microswitch) and insulate that termination.
Try the grill. If it doesn't stay lit you still have a fault somewhere, maybe the thermocouple or a loose connection.

 

[brianmoooore]

IIRC, some (all?) microwave ovens have door switches that are NC to switch off the magnetron when the door is open, but also have NO switches, connected across the magnetron supply to ensure it is off with the door open.
Trial and error could result in a big bang!

 

[Avo Mk8]

IIRC, some (all?) microwave ovens have door switches that are NC to switch off the magnetron when the door is open, but also have NO switches, connected across the magnetron supply to ensure it is off with the door open.

This one is a thermocouple in the flame wired via the microswitch to the solenoid in the gas valve for the grill.
Incidentally axisus, that metalwork/ground tag needs to be well connected to the metalwork that the gas valve is mounted on for this to work. You presumably used the original earthing point?

 

[brianmoooore]

IIRC, some (all?) microwave ovens have door switches that are NC to switch off the magnetron when the door is open, but also have NO switches, connected across the magnetron supply to ensure it is off with the door open.
Trial and error could result in a big bang!

Is there another thread running about microwave ovens, or is it approaching senility that makes my eyes read microswitch and my brain see microwave?

 

[Avo Mk8]

Is there another thread running about microwave ovens, or is it approaching senility that makes my eyes read microswitch and my brain see microwave?

Oh I thought your post about microwave door switches was informational, albeit a bit random!
I think the connection between what my eyes see and my brain thinks gave up a long time ago

 

[axisus]

Thanks all, I have finally worked out that the microswitch is the problem. I bypassed it by connecting the two wires together and the grill works. New microswitch required!

It's a very old worn out oven and I'm hoping to replace it soon, I just like to use the grill!