Vauxhall Astra - problem with brake/side lights - help please!

Sounds distinctly like a short circuit between the tail light circuit and the brake light circuit. When one of these circuits is operated, the feed simultaneously operates the other circuit it is short-circuited with.

This could be quite an involved check as the wiring involved (at least on the sidelight side) runs the whole length of the vehicle. It would not be too difficult to narrow the area of the fault down if you have access to simple multimeter able to measure resistance. If you feel you can do this, let me know and I will give you a run-through of what to check. Even if you don't find the problem, it could save some money on a garage bill.

HTH

Anthony Remove eight from email to reply.

If its only one side it could be that the earth connection to that sides' light cluster is disconnected or high resistance. The current is then passing to earth through the other bulbs' filament, rather than directly to earth, and that causes the other bulb to light.

If both sides are affected it is probably a short circuit somewhere as the light clusters are normally earthed independently and it is unlikely that both earths have failed.

Andy Graham

Assuming the stop lamp filament is in the same bulb as the tail lamp, this can happen if one of the lamp filaments has blown but has shorted to the other circuit within the bulb.

To eliminate this before things get too complicated, remove one of the stop/tail bulbs and check if everything except that bulb works OK. If not, replace the first bulb and remove the other stop/tail bulb. Check as before. If temporary removal of a bulb clears the fault, try with a new bulb.

If none of this cures your problem, you may need specialist help unless you can use a multimeter.

HTH

Chris

sounds like incorrect bulb type (single filament in a twin holder)

faults like this are easy enough to fix at small independent garages and are unlikely to cost much. I do repairs of this nature frequently.

mrcheerful

Sounds daft but if you have changed a lamp recently check that the plugs are correctly inserted/orientated into the lampholder.

Tom

Very many thanks for everyone's help with this - what a helpful lot you are!

Tt turned out that it was a bulb that was causing the problem. I replaced both brake light bulbs and things returned to normal. A short in one of them, maybe?

Cheers

Jerry