Is there a replacement part for the BN4 temperatur regulator?

[DrElch]

I've inspected the BN4 temperature switch /thermostat recently and I have the feeling that it doesn't work anymore. there is no connection between the two electric points and the switch doesn't do anything, so I assume it is broken.

I was not able to find a part number for it and I don't seem to find any part that is a replacement or similar to it. Repairing seems difficult as the body of the switch is riveted shut.

Does anybody know more about this part? Or can help me finding a replacement / similar part?

For clarification it is part no.9 in the following diagram:

[notchboy]

This switch is just an on/off point to shut off the pump from stoking an already lit fire for the furnace. Some people remove it and connect the two blue wires closing the break.

The gas heater is meant to cool down in 30 to 50 second intervals that this switch controls. The metal spring opens up as heat goes up, it then presses the bottom button on the microswitch you believe to be bad. This in turn turns the fuel pump off untile the fire dies, cool air then reduces the spring allowing the button to depress. Fuel pump then reactivates, spark plug ignites the fire and the cycle continues.

I posted you a lead on a new thermostat. They are out there in both new and used. I dont think they can be repaired.

More info - https://www.facebook.com/groups/1029635500462666/
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[hylomatt]

Check German supply as well.

http://www.germansupply.com

[busdaddy]

That microswitch isn't anything special, if it's the problem most electronic supply stores should have an equivalent in stock.
The bimetal coil does change shape over time, especially if salt has been involved, the split axle it's mounted on can be rotated in the housing to change it's operating range. It's handy to have an oven or other adjustable heat source to calibrate it, but it doesn't have to be exact and can be done at room temperature, just confirm it's within the range of the cable movement and capable of opening the circuit on a warm day. Most working OG ones I've had required pulling the cable fully out to fire the heater on a summer day, in the winter they worked with the cable pushed all the way in.
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