Headlight Aggro (1 Viewer)

[DevonBen60]

In the UK LED head lights are not allowed by vehicle testing stations. So each year standard lamps must be installed before the MOT test then LED headlights refitted afterwards so you can actually see where you are going when it’s dark!

Anyway this year after fitting the standard headlights a strange thing occurred.

When the engine is off, all lights switch on and off correctly. But with the engine running, the right hand headlight comes on when the side lights are turned on.

The wiring diagram shows a relay and a diode but I have been unable to locate them. Can anyone please advise where they are or what to do?

I have checked all switches, lamps and fuses which are ok

 

[OSS]

But with the engine running, the right hand headlight comes on when the side lights are turned on.

Is the right headlight that turns on but shouldn’t kind of dim? Or is it standard brightness?
If it’s dim, my suspicion (as usual) is there’s a ground issue.
The side marker lights and headlights and gauge lights all join up into a single connector using spade connectors. If aftermarket headlamps are used, the increased current can cook that connector creating weird grounding problems.
Whenever something turns on that shouldn’t when something else is flicked on — always suspect a compromised ground (somewhere).

The common ground connector for the lights is located behind the instrument cluster, tucked in behind the wiring harness. It’s a plastic coated thingy with a bunch of wires entering it.

Search this forum for “floating ground”.

 

[DevonBen60]

Is the right headlight that turns on but shouldn’t kind of dim? Or is it standard brightness?
If it’s dim, my suspicion (as usual) is there’s a ground issue.

It’s normal brightness. I thought about grounds but why is everything fine when engine is switched off?
I’m thinking it must be something to do with the relay if it’s only an issue with engine on but why just the one side?
A diode is marked on the schematic (European 4 headlight version) near the relay but I have been unable to find it to test. Perhaps it has shorted allowing current flow in the wrong direction??