One headlight working at one time

Euphoria1z

Hi

Got a weird problem with my head lights. car is a volvo s40 2003.

My left head light stopped working, didn't look blown but bought a new one which still didn't work. Thought maybe loose wiring, so took the right bulb out and put it in the left and it works, so not the wiring. Took the left bulb which had stopped working and put it in the right hand side and it works. So the bulb isn't blown.

so basically only one bulb works at one Time?

What's causing This?

DUTR

Have you checked the fuses?

Inner_Zone

Sounds like an earthing issue.

Euphoria1z

Yes checked the fuse their fine.

Both sides work only one at a time so how can I check it's an earth issue?

Inner_Zone

Euphoria1z wrote: »

Yes checked the fuse their fine.

Both sides work only one at a time so how can I check it's an earth issue?

Trace the wiring back. Maybe a poor and or correoded connection (possibly several) to the body.

colino

Ah for the good old days of blown bulbs or fuses. I hope that by a little wiring check you will find a duff connection, but failing that, price up a CEM on ebay.

Paradigm

Check the headlamp relay, some fail due to the solder cracking... common on Saabs.

Norman_Castle

This Volvo forum is very helpful http://www.volvoforums.org.uk

SuperAllyB

Ask the police. Quite a few of their traffic cars seem to have this problem when they're following me.

DUTR

SuperAllyB wrote: »

Ask the police. Quite a few of their traffic cars seem to have this problem when they're following me.

It could be that the Op's car is an ex police car.

Joe_Horner

Fairly classic sign of a bad earth if both lights use a common earth point. A bad connection / high resistance at the earthing point will pass enough current to light a single bulb (you'll find it's dimmer than it should be but may not be easy to notice) but, when you try to pass double the current for 2 bulbs, the resistance limits it to not enough to light either.

Simple test is to connect a wire from the earth side (make sure it is the earth side!) of one bulb to a good earth point (clean metal or the battery -ve). If they then work normally, it's an earth fault.