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I have a problem with my head lights, they flash on and off. So far I changed switches and the spades which I thought the problem was.
Still the same so it may be the thermal breaker. Where is this located? It does have I believe it has 50watt bulbs fitted.
Can the thermal breaker be removed and a fuse fitted? Just a thought.

The thermal breaker is located below the dash on the driver's side adjacent to the door. It is rated at about 26A to 28A. Clean the contacts gently with an emery board used for fingernails. If the lights are still flashing regularly then there is a fault in the lighting circuit and not the cutout. Get the lighting circuit checked as a safety precaution anyway.

I would also check the headlight dip switch and the wiring to it. The wires and connections there are quite weak and may be failing.

In theory you could replace the cutout with a 30A fuse but you must ask yourself why did Vauxhall use a breaker rather than a fuse? Just think of a fault in the lighting circuit which caused the fuse to blow at 60 mph on a remote and dark corner.... or a fault that causes the thermal breaker to flash on and off... The latter would give you a better chance of negotiating the corner to safety and also give you a better chance of getting home too.

Have you ever has an old light bulb blow in the house and it took the fuse with it too? The same situation could happen in your car. A thermal breaker would cope with that type of fault without a problem.

There are modern resetable breakers and thermal breakers rated at 30A and if you must replace the original then these would be preferable to a fuse.

Thanks for that, when I was driving the car home the second time they started to flash was just after Grantham on a dark road. No fun at all. I will start checking the system. Another way I suppose would be to incorporate a relay to feed the lights to reduce any load. I will have a look.

A relay is a good option but you will still need to fuse the lighting circuit....back to the possible downsides of using a fuse.

The most likely culprit is a short in the circuit, followed by a dodgy dip or main headlight on/off switch followed by the cutout being faulty.

Check that the wiring to the connectors on the back of the bulbs is properly covered and cannot get wet.

I have checked the column switch which is ok, reminds me of the old Land Rover type. The Thermal I have took out is a 25amp, I have checked my spares and found 25amp and 35amp ones.

That makes it easy, just check the thermal cutout by substitution. If it still misbehaves then it is definitely a short circuit or water ingress that is causing the problem.

I have just tried a 35amp first to see what happens and I had no problems, would this be a bit high? seeing as a 25amp was fitted. I can't find any mention of the rating in manuals.

As I read it - the current draw is basically the wattage of the bulb(s) divided by the voltage, so add up all the bulbs in the circuit and divide through. That assumes no (or little) resistance in the circuit, and this resistance (either by poor contacts, or even breaking down wires in the loom) is what is increasing the draw.

The downside of putting anything too high in place is that it might not give the same protection. If your original 25a breaker was only just enough for the job, moving to the 35a one hasn't fixed it, you've just masked the issue as I'm sure you know.

I well remember fitting some spotlamps in my main beam circuit on an old 1800SL I used to run. All was lovely until I got into this dark country lane and flicked the main beams on, which also brought my lovely spotlamps on. Shortly before the first sharp bend, total darkness for a second or so while I scrambled for the dip switch. That was "interesting".

The Service training manual says......





I would suggest trying your spare 25A one for the sake of safety.

Interesting, it says do not clean the contacts?