Driving light issue

[Telf 222 2 Cars]

My driving lights aren't working.

 

Bulbs are good. Relay on fuse box is OK. 

 

My main beam works fine .

 

I have redone the earth points behind the headlamps with a bolt and nut affair.

 

Heres the weird bit.

 

No lights on resistance at the earth's is 1 ohm to battery.

 

Put the main beam on the resistance shoots up to 1.5k.

 

The resistance at the driving light earth at the actual lamp is 3k.

 

With lights off everything is as you'd expect zero ohms or there abouts.

 

So it seems I have a high resistance to earth but when the lights are on.  

 

I've checked all the earth cables separately.  All 1.5 ohms. Checked for random voltage on them . Nothing. .

 

I've even rum a cable from the driving light to the battery terminal and I get a high resistance at the driving lamp.

 

This makes no sense to me at all. Anyone got any ideas ?

 

I've even removed the dim dip relay just in case and that makes no difference at all. Oh and swapped the dash lights stalk but as expected that wasn't the issue either.!

 

 

[Telf 222 2 Cars]

i mean i suppose the high resistance must be a bad connection that isnt coming to light until the high beam is turned on eg there is load there but i cant for the life of me find it!

[Gaz D 5]

Sounds like a short between the driving lights switch wire and earth. Do you get a resistance reading between the earth and any of the switch outputs?

[Telf 222 2 Cars]

A short would pop a fuse or have a live voltage on the earth . That's not happening. 

 

It's a relay switched supply to the driving lights with good voltage at the lamp. The Earth from the lamp on runs a foot direct into an Earth stud.

[welshpug 1,622]

Those 2 pin yellow unsealed plugs are quite vunerable, give them a good wiggle and they might start working.

[Telf 222 2 Cars]

7 hours ago, welshpug said:

Those 2 pin yellow unsealed plugs are quite vunerable, give them a good wiggle and they might start working.

Wouldnt I have a high resistance through there end to end on the line? I hate car electrics !! 

[Telf 222 2 Cars]

Fixed!

[Telf 222 2 Cars]

To close this out for anyone who might read this in the future.

 

Fixed by renewing the earth studs behind the headlights.

 

Cut the yellow connectors out that feed the driving lamps and cut the cable back to remove corroded cable hidden under the cable insulation. Re terminated with standard connectors and sealed . 

 

 

I had crazy multimeter readings, voltage, current and resistance that made no sense, I suspect because of the way the main, dipped and driving lights circuits are interconnected. 

 

Further notes:

 

Driving lamp relay is the far left one in the fuse box.

 

Dim,dip relay is in the engine bay next to the horn relay behind the coolant expansion tank.

 

The dip, main function is direct from the dash stalk with no relay.

 

Hope this might help someone 

 

Cheers guys