Failed MOT, finding the earth fault! Help or ideas?

[fairwynds]

Grrr, took van in for MOT today, and it failed for the first time in years
No headlights. Sidelights ok, main beam flash ok, ust no dipped beam. In last few days have done some work under dash re trailer towing relay, and I think Ive disturbed the pixies that live under there!
We tried finding the fault (believe its an eathing issue) at the testing station, but no luck. So tomorrow, I will be mainly 'polishing my crowns!
Fingers crossed please.....

[fairwynds]

Any ideas greatly appreciated..
have a sea of wires in front of me, and a Haynes manual. Trying to get to grips with the wiring diagrams.
Ok, so here's whats what so far:

Symptoms:
No headlights (no dipped or main beam). Sidelights ok and I can FLASH main beam. Also no rear fog light (because of no headlamps I'm guessing?).

Have unscrewed the (early type) fuse box, from passenger side (RHD van).
There are a row of 12 'old style' fuses and looking at Haynes they number left to right and include:
1 - left hand tail light, parking light and side marker lamp
2 - right hand tail light, parking light and side marker lamp, number plate lamps, foglamps
3 - left hand dipped beam
4 - right hand dipped beam
5 - left hand main beam, main beam warning lamp
6 - right hand main beam

Im currently not getting any power into the rear of the fuse box at Nos 3, 4, 5, 6

Everything else seems to be ok at the moment.

Any ideas please?

[fairwynds]

So far have removed all the earth connections from the two earth crowns under dash... 6 x single wires and 3 x doubles.
Have tried to isolated what earths what and so far can only confirm the following circuits:

heater blower motor (but this doesnt isolate the wipers/washers)
windscreen washer pump
drivers side interior light

so I have 3 x single and 3 x double earth connectors that, so far, I have no idea what they earth. Everything else on the van seems to be working ok!

Had hoped this would be an easy job ie: this earth is corroded, clean it, hey presto, headlights! No such luck.

Maybe the headlights have an earth elsewhere...? They still don't bliddy work!

[fairwynds]

Taken these off too, to be cleaned..

[pionte]

dont shout at me .... but you have checked the bulbs themself ??

[fairwynds]

dont shout at me .... but you have checked the bulbs themself ??

(queitly sneeks out to van to check )

...that said, I can flash the main beam....?

[pionte]

if your have just one main bulb and one side light bulb then you will have 2 filaments inside the main bulb, one for main beam and one for dipped beam, it is quite usual for just one filament to burn out . Take the bulb out and visually check, you can usually spot if one has gone... failing that put it on a battery to double check.

The main beam and dipped beam are either separate bulbs or as I say dual filament .
if its a halogen bulb then its a good idea not to touch the glass with bare hands, this can leave oils from your skin on the surface that may lead to a hot spot and premature failure, if you do then just best to give them a wipe with an alcohol based solution like methylated spirit or similar.

martin

[fairwynds]

will get back on this after weekend.. but I'm suspecting the switch on dash at the moment...

[Ralf85]

Sounds like the problem and cheap to fix if it is!

[1_eyed_jim]

Always good to clean those crowns though!!

[camperclan]

Had something similar on ours it was poor connections on one of those earthing crowns,and that was after i had messed with fusebox...Nick.

[Mark Foss]

Clean your earths up (that's always a good shout) Recon its most likely the switch as you have proved that you have an earth to the lights as your main beam + sidelights work. Pull out switch and check you have power going outbound to the headlights with a meter.

[fairwynds]

Clean your earths up (that's always a good shout) Recon its most likely the switch as you have proved that you have an earth to the lights as your main beam + sidelights work. Pull out switch and check you have power going outbound to the headlights with a meter.

Well, did just that, having cleaned up all the earth crown connections (never a bad thing). No power leaving the switch. When I played with the switch itself, pushing it up and down, rather than side to side, it worked, but I had to keep my finger on it! Swapped switch from another van temporarily. Problem solved. Now just need to clean up the insides of the old one...


ps - MOT retest passed just now

[AdrianC]

Ok, so here's whats what so far:

Symptoms:
No headlights (no dipped or main beam). Sidelights ok and I can FLASH main beam. Also no rear fog light (because of no headlamps I'm guessing?).

This isn't sounding like an earth fault, then.

Have unscrewed the (early type) fuse box, from passenger side (RHD van).
There are a row of 12 'old style' fuses and looking at Haynes they number left to right and include:
1 - left hand tail light, parking light and side marker lamp
2 - right hand tail light, parking light and side marker lamp, number plate lamps, foglamps
3 - left hand dipped beam
4 - right hand dipped beam
5 - left hand main beam, main beam warning lamp
6 - right hand main beam

Im currently not getting any power into the rear of the fuse box at Nos 3, 4, 5, 6

Even less like an earth fault.

OK, so quick and easy "Is it earth or not"? Go and remove a headlight bulb. You've got a multimeter, right?

Have you got a good earth to the earth leg of the socket?
Have you got +12v to either/both of the other two?

My money, right now, is on the switch. If there was no live feed, you wouldn't have flash. If there was no earth, you wouldn't have flash. If the switch is sulking, then it wouldn't be giving a feed to the rear fog.

[fairwynds]

Ok, so here's whats what so far:

Symptoms:
No headlights (no dipped or main beam). Sidelights ok and I can FLASH main beam. Also no rear fog light (because of no headlamps I'm guessing?).

This isn't sounding like an earth fault, then.

Have unscrewed the (early type) fuse box, from passenger side (RHD van).
There are a row of 12 'old style' fuses and looking at Haynes they number left to right and include:
1 - left hand tail light, parking light and side marker lamp
2 - right hand tail light, parking light and side marker lamp, number plate lamps, foglamps
3 - left hand dipped beam
4 - right hand dipped beam
5 - left hand main beam, main beam warning lamp
6 - right hand main beam

Im currently not getting any power into the rear of the fuse box at Nos 3, 4, 5, 6

Even less like an earth fault.

OK, so quick and easy "Is it earth or not"? Go and remove a headlight bulb. You've got a multimeter, right?

Have you got a good earth to the earth leg of the socket?
Have you got +12v to either/both of the other two?

My money, right now, is on the switch. If there was no live feed, you wouldn't have flash. If there was no earth, you wouldn't have flash. If the switch is sulking, then it wouldn't be giving a feed to the rear fog.

...spot on, thanks for the info and picture. All working fine now (just got to put the old switch back together now)