Thermal Overload Circuit Breaker

[jpsmit]

This is just a fusible link isn't it?

Is it reliable? Or should I replace it with a fusible link or even a high amp fuse (and if so, what amperage?)

[dann01]

They work pretty well. They are bi metal strips which open the lighting circuit when they get too hot... I have had them open only a couple of times during Viva ownership since the early eighties, and that was when I'd driven nearly 8 hours continuous using high beams quite a bit.

If you replace with a fuse link, don't rate too high, otherwise you'll negate the reason for it in protecting the wiring.

Dan

[1972nail]

Yes, as Danny says, they are pretty reliable with the original lighting setup. The thermal circuit breaker is an automatically resetting circuit breaker rather than a fusible link or a high amp fuse. Adding extra lights or bigger bulbs is what causes problems with this device.

If you're fitting relays to the headlight circuit then the load on this will be greatly reduced and it will never open. It's rated about 28A, I think, but the total current without the headlights on that circuit is about 5A. You can leave it in place, but with the reduced load it will be very overrated as a protection device and therefore ineffective.

Therefore you should consider replacing it with a normal fuse of about 10A to protect the remainder of the lighting circuits which still solely depend on it for protection. That will amount to the dash lights, side lights and the switching current for the headlight relays.

I just fitted a modern 10A blade type fuse in it's place between the spade connectors.

[vauxhallbitz]

Went for the MOT today and when I got the car on the ramp I had no side lights. The fuse is OK but I have not checked the voltages yet, I see on the wiring diagram that there is a fusible link which feeds the sidelight circuit, the question is, where is it situated??