Dim headlight - earth fault?

[r.welfare]

Right, I'm typing this having spent 4 hours taking the front of the 405 apart, fiddling with stuff, swearing a bit and then putting it back together again. And still not getting the front bumper properly aligned, but that ain't the big issue...Basically, the nearside headlight, on dipped and full beam, is noticeably dimmer than the offside. When on full beam, the nearside indicator also lights up a little, and retains this glow when the lights are flicked back to dip - but doesn't do it when you go to dip from them being off, or on sidelights. If you put the indicators on, the main beam bulb (it's the model with a separate diddy main beam bulb) pulses a little in time with the indicators' flashing.So I thought "earth fault", pulled both headlights out (GR8 fun, you need to take the bumper and grille off to remove 'em), lots of electrical contact cleaner and emery paper on the connectors, undo and reseat all the bulbs. Also, I tracked down (visually, I'm crap with a multimeter) what I thought was the earth for that circuit (attached to the inner wing just behind the headlight), undid that, cleaned it up and put it back together.But it's still the same.Any thoughts - am I missing something obvious? Other than it's a 16 year old French car of course, and if this is the only electrical fault on it I'm doing well...

[VWPowered]

defo an earth fault check all lights not just the front

[Pete-M]

Whack a jump lead from the earth on the headlamp to the engine block or summat. If it goes bright, it's the earth...

[garethj]

Whack a jump lead from the earth on the headlamp to the engine block or summat. If it goes bright, it's the earth...

What he said. I've made a handy new tool for this kind of thing, it's 2 12ft long wires with croc clips on 1 end and spade connectors on the other end. I put the croc clips on the battery then I know I've got a good 12V on the spade connectors.Prod them onto the bulb to see if things improve, take the positive wire off and see if it goes dim (unlikely in your case because the indicator is glowing), then take the earth wire off and see how it looks.It's also a handy thing so I can take 12V to the horn, wiper motor or anywhere else to see if it's the swtch, fuse or the thingy itself that's duff.I'd stake what's left of my reputation that you've got a bad earth on the headlight so it's finding a path to ground through the indicator bulb.

[r.welfare]

Thanks chaps. I forgot to mention I swapped the complete headlight for a spare unit, just to see if it was the headlight itself - but it wasn't. The croc clips to battery wire will confirm, I guess, whether it is (as I suspect) that the earth wiring from headlight connector back to earthing point is stuffed - I'll try and do that test tomorrow.

[simmo]

Does sound like a poor earth but Dim-Dip units, if fitted, can cause some weird faults maybe worth a check if a good earthing doesn't sort it out