Double filament bulb problem.

[seabod91]

Good morning all. I have a 2003 focus mk1 that I have a problem with. I thought it was just a simple blown bulb, but it turns out even with a new bulb the rear light are working fine, but the offside brake lite isn’t working. I am going to get a new battery for my multi meter soon to probe around. I have checked the wiring where it traces along the boot area and also the Earth that is there look all good. Any suggestions on what to look for. And best way to check with a multi meter.

Cheers. Sean.

[Panamax]

I'd start by swapping the bulbs you have left to right on the car and see what happens. i.e. to rule out bulb faults.

If the rear light is working correctly you don't have an earth fault, the fault will definitely be on the actual connection between brake light switch and bulb.

I'd start by peering into the socket with a torch to see if there's damage in there. Also behind the socket if possible. Fairly obviously once you have a multi-meter or just a test bulb on a piece of wire you can get someone to press the brake pedal while you check the terminal in the socket.

If all else fails you can bodge a fix by simply connecting a new wire between the two brake light sockets.

[seabod91]

Cheers for the reply. Just swapped the brake light holders around and it’s the holder that is faulty. Will order a new one tomorrow.

[Panamax]

Bingo!