Where would a common earth for headlight be?

[Gromit]

Late last night, heading down the motorway in the hammering rain, the head lights started flickering occasionally - both sides simultaneously. Same symptoms when on dips. I could hear arcing over the radio speakers.

Wiggling the main light switch and headlight switch/flasher didn't change anything. Dash lights were unaffected.

I'm guessing that a common earth to the lights didn't like getting wet. As it's so intermittant, I can't start tracing it unless it reoccures, but was hoping to have a look at/clean up and common earth points for the lights.

Any pointers where to start?

Mucho thankos.

[LandyManLuke]

Screwed to the inner wing. It's pretty horrible. I ran new earths back to the battery.

You should be able to seethem looking in from the bonnet, or through the headlamp hole.

Also watch the connectors on the back of the headlights, I had an issue when they went intermittent.

[Gromit]

Good stuff, thanks a lot

[pete3000]

There isn't a common earth as luke has said, it's to each wing seperately. Points to a body or engine earth fault where a single path is used if it flickers both sets together. Don't spose you hung your head out the back to see if tail lights were doing it as well.

Pete

[Mo Murphy]

On the TD5 don't the earths go back to a common earth point on the bulkhead via the wing harnesses ?

Mo

[Maverik]

If both lights are flickering together then 1) it could be a common earth problem but as the lights are eartherd locally, the only common earth will be one of the woven check straps comming off the gearbox to the battery. I'd say if that was problamatic you'd see other faults too... could be wrong. or 2) its a supply problem, what age vehicle is it? if its old like mine (85) then no relays so all the power goes through your switch gear - could be a problem with a switch. If later model with relays, are all your relays dry?

I'm just repairing/re-building my harness, putting in relays etc.

If you need any pic's just holla.

Mav

[LandyManLuke]

That's the local earth I was refering to, if the vehicle's a td5 it may well not be present, I don't know.

I agree that if both are flickering together, it is unlikely that one of these earths is the sole cause, but they're still worth checking, and they definitely aren't a good solution.

[PaulMc]

On the TD5 don't the earths go back to a common earth point on the bulkhead via the wing harnesses ?

Mo

Mo is correct

On the TD5, all the front lamp earths go back to a single earth header, mounted on a bolt on the bulkhead -

Everything else in the engine bay (except the starter motor) and all of the earth headers in the dash and behind the instruments also go back to this point -

C0550's mounting bolt is also used to earth the ABS Modulator (on it's own earth cable) via ring terminal C0362 -

I would run an additional earth cable (of at least 16mm²) from C0550/C0362's mounting bolt, directly back to the battery earth terminal.

.

[Maverik]

No, not ideal, to save on wireing I was debating on extending the earth to a direct chassis connection. Then just making sure I had good negative check straps at the other end.

[Gromit]

Super info - thanks

[Mo Murphy]

Mo is correct

Thanks Paul

I'd be inclined to throw another headlight switch in there and see if it improves things as these are notoriously unreliable.

Mo

[pete3000]

I was wrong, i should have read it was a td5, with new fangled earthing. Changed from my 87 110.

It Seems a bit over optomistic to send that much to a panel earth? with the whole galvanic steel/alu corrosion thing going on.

Pete

[Mo Murphy]

IIRC the TD5 also has a braided earth strap from bulkhead to chassis.

Mo

[SwankyPete]

On 7/13/2010 at 8:16 AM, Maverik said:

If both lights are flickering together then 1) it could be a common earth problem but as the lights are eartherd locally, the only common earth will be one of the woven check straps comming off the gearbox to the battery. I'd say if that was problamatic you'd see other faults too... could be wrong. or 2) its a supply problem, what age vehicle is it? if its old like mine (85) then no relays so all the power goes through your switch gear - could be a problem with a switch. If later model with relays, are all your relays dry?

I'm just repairing/re-building my harness, putting in relays etc.

If you need any pic's just holla.

Mav

What wheels & Tyres you running here Mav? looking to upgrade my 90 with something like these?

[cackshifter]

I'd suggest as per Mo the problem encountered by the OP may well be the light switch on the steering column, as these arc eventually. The heat melts the plastic the contact studs are in, and eventually there is no contact. Try a bit of gentle judicious jiggling of the switch when the headlights are actually on, ie when the ignition is on too. It might also of course be the relay in the headlight feed or the dip switch but the column switch has to be prime suspect, assuming the lights aren't relayed.

[Maverik]

Holy thread revival 🤣

Fyi i hated that tyre rim combo, was something like 265 75 R16 General Graabber AT2 on modulars used to corner like she was on rails in the dry, but i found wet weather performance especially through big puddles sub optimal to the point of dangerous!

I hate overly big rubber i dont like much over the standard 235 85 R16 these days on wolfs or a decent set of early period LR alloys.