Forums Forums Enthusiast Forums A - Z Autowirral Car electrical advice

I think I may have a issue, (well to be honest I have a few, but just want to sort this out first)

When I disconnect my 2 earths on back lights, 1 for each side, the lights are still working,

For instances, my stop and tail lights has 3 wires, 1 earth 1 for stop lights 1 for tail lights, if i disconnect the earth, the bulb still lights up.

It is not caused by bulb earthing through light houseing, as the housing is all plastic.

The lights are earthing back though other bulbs if you put indicators on at the same time the tail lights will dim as the indicators flash . why do you disconnect the earth's any way ?

Because if i keep them connected the revs drop when i switch on headlights

Have you checked the engine earth's make sure good conections from battery to chassis and engine to body. a quick check for this is put a jump lead from engine to negative on battery and see if problem persists !

They are all new earth leads, and are all clean, and have put extra earths on.

all points towards alternator I see from one of your other posts this has been changed why did you change it ? ie was this fault there before changing the alternator ?

The fault was not there till alt dies on me, i got alt fixed, and then it started, so i got brand new alt, fault still there.
put a ford genuine alt on, and some of the other symptoms i had have gone, but still left with this one.

That dont sound good. poss original prob may have damaged ecu /body control module sorry cant be of more help .

Its had a new ecu fitted, that was running on car i took it off perfect.

I still believe its a earth fault. But finding it, is proveing impossable.

So the only problem you have is with the rear lights? There are no other electrical problems with the car?
Was the alternator overcharging?
The brake lights are only earthed when the brake switch is closed - this is located above the brake pedal (usually) - stick your hand above where the brake pedal is and fish around for two wires and a plunger switch. These are pretty standard on all cars, I've had a couple go myself, when they brake the lights stay on. Just an idea.