Tail lights adversley affected by use of other lamps (this is what it failed for)

[johnw7752]

The tail lights go ever so slightly dimmer when the full beam/fog lights are put on.
I have cleaned 2 earths that i found in the engine bay and also checked all bulbs, connections in the rear light cluster, they all seem to be ok. Any ideas as to the cause of the problem?

(upon taking the earth strap that comes straight from the negative side of the battery off, there were a lot of sparks coming from where the strap connects to the car body, the connection was cleaned really well and reattached, this did not solve the light problem but appears to have drained the battery as the car wouldn't start after this and jump leads needed to be attached. Just thought this may have some bearing on the light problem)

 

[Rob669]

You've failed the MOT test I take it?

The problem is usually the rear light cluster contacts shorting out. Take them off and clean with electrical spray (Maplins sell it) and wet and dry paper. Mine had this problem, but I only got an advisory at the test.

 

[MicKPM]

As above, clean all earths and connections to the rear light clusters.... 30 minute job and real easy restoring all manliness.