Headlights cause windscreen wipers to go

[eds]

My wipers go off every time i use the headlights in any way. That means turning them on, off, dipping, flashing, anything involving the headlights.

So far I have put an isolation switch in the wiper circuit so I can disable the wipers when it is not raining which definitely helps. This is only a partial solution as I still find the wipers dry wiping, labouring across the screen at zero MPH. It hurts to watch.

I expect the responses will point to a scuffed wire somewhere causing a short circuit but I am only guessing.

Has anybody got any ideas where to look?

All help greatly appreciated.

Thanks in advance

Ed

[western]

take the left hand lower dash corner off & check the wiper motor earth [black] wire is connected to the body & terminal on the bulkhead.

it's difficult to visually check all the wiper wiring as it's hidden within the dash, only way is to dismantle the dash & physically check the wiring.

[GBMUD]

Yup, check out the earths. There is another big one on the bulkhead in the engine bay near the clutch master cylinder. Check also the earth strap from the body/bulkhead to the battery.

Chris

[eds]

Thanks so far

What am I checking when I am checking the earths. Just that the bolt is done up nice and tight and that there is no corrosion?

I am not clever enough to understand how the earth would trigger the wipers with the headlights. I thought it may be a bit of electricity leaking from a headlight cable to the wiper cable. I thought that if the earth is poor then the wipers or headlights would not work at all.

I have had the dash apart to redo the wipers and gear so that means new wiper motor too. That was a different problem caused by so much dry wiping. I tried to do a visual on the cables but they all appeared ok.

Thanks

[steve200TDi]

Hi,

My wipers also come on when ever I put the lights on/off, main/dip. I might have a look at the earths as well.

Steve

[Guest diesel_jim]

Thanks so far

What am I checking when I am checking the earths. Just that the bolt is done up nice and tight and that there is no corrosion?

I am not clever enough to understand how the earth would trigger the wipers with the headlights. I thought it may be a bit of electricity leaking from a headlight cable to the wiper cable. I thought that if the earth is poor then the wipers or headlights would not work at all.

You're kind of right....

If an electrical item (say, a CB, wired in you yourself), is connected with +ve and -ve to the battery, then if either wire is broken, then it'll not work, period.

But on a car, to run a -ve back to the battery for every accessory would make the wiring a huge big mess of cables (the +ve's are usually individually fed, or at least in small groups of items, so that they can be individually fused)

so the earths (-ve) are connected together in clusters, back to a "header joint", which is where several, or several dozen, earths, are connected together and (usually) bolted to a metal piece of the bulkhead, to give a nice earth connection.

Now, if an earth wire is broken for any particular item, then electricity, a bit like water leaking from a pipe, will try to find it's way somewhere....

this could result in two items (like headlighs and wiper motors) which might possibly share the same header joint, getting a "back feed" of electricity, so 50% of the power goes through the item you want to operate, and the rest going through something else.

[eds]

Here we go, another chase round the Landy....

This started off about the wipers/headlights. It is an old issue.

I was also pulled over twice this week for having no dipped light on the drivers side. I thought the two problems unrelated, just a bulb issue. It failed a couple of days ago.

When I went out to have a look for these earths I decided to change the bulb first.

Guess what, now I don't have dipped on either side and it is not a bulb issue. The other side decided to give up in sympathy i think! No reason, just did it in front of me. Also for the first time the cab light did not turn on straight away - a 30 second delay. Is it all one bad earth?

I would get on and check these earths as they sound related but with all the rain it is not conducive to electrical chasing.

The fuses are ok.

I was wondering whether there was anything else to check other than the earths.

Thanks thanks again.

Ed

Added - I have searched and read and it's all about the earth so sorry for asking when i've already been told! Ed

[GBMUD]

See the big earth point I mentioned above on the bulkhead. It should be clean, uncorroded and tight.

Chris

[steve200TDi]

Yup, check out the earths. There is another big one on the bulkhead in the engine bay near the clutch master cylinder. Check also the earth strap from the body/bulkhead to the battery.

Chris

I also have this problem. I have checked the earth on the wiper motor by moving the earth to the door check strap bar, but it still happens. Where is this large earth you speak of in the engine bay near the clutch master cylinder as I can't see it.

Steve

[western]

should be a bunch of black 'earth' wires between the glow plug relay & the fuel filter, held by a single largish screw head on to the bulkhead [marked in yellow on this photo I've taken from my 110

[steve200TDi]

should be a bunch of black 'earth' wires between the glow plug relay & the fuel filter, held by a single largish screw head on to the bulkhead [marked in yellow on this photo I've taken from my 110

Excellant, thanks for that I have a look and see what I can find.

Steve

[eds]

I've checked the 3 earth points mentioned but no difference yet.

One far side dipped beam still not working and wipers still go off.

Are there anymore earthing points which could be pointed out to me?

The near side dipped beam fails intermittantly and the courtesty light has gone altogether now.

Thanks again

Ed

[western]

try pulling all the fuses & cleaning the end caps & fuse holder clips, tighten the clips a bit by squeezing them together & refit the fuses,

each set of front lights has a earth behind each side bolted to the vertical part of the inner wing, easiest to drop the lights out & work through the headlight hole for access.

[eds]

Today I took all the front headlights apart. Replaced the indicators and sidelights units for new and replaced the main headlamp wires as the plastic looked a bit melted.

The result is that the headlights all work again but the wipers still go off when the headlights are used.

I have noticed that it is not as often but it does still occur. It is not predictable and happens often enough to be annoying ie once every 6 headlaight changes ie on/off dip/dazzle flash etc.

It looks like it is an earth but not sure where to look next.

Do I have to do the rear lights too to be certain.

Has anybody had this problem and solved it before?

Thanks everybody for helping

Ed

[western]

take the column surrounds off & check carefully the wiring from each of the stalks & main lighting & rear fog switches, have you tried a new or known good main lighting switch ?

[eds]

Thanks for that

I changed the lighting stork first as the horn cable had broken so probably not that, it did it with the previous stork and I did not get a third stork as assumed the new one was ok.

Anymore clues?

[crazyfarmerboy]

i have had this kind of thing before. check wires as they come in and out of the bulk head to see if the insulaiton has rubbed off exposing the bare wire. This usually happens in places where there is a sharp edge. if so either replace the wire but i would cut the section out and add a new bit with joining blocks. if there is no room just wrap the worn though bits with electical tape. hope this helps.

[eds]

I've tried everything with no luck so am now giving up until I get frustrated again!!

Thanks for all the help

[western]

were the earth points behind each of the front light locations in good order/clean/secure, attached to the outboard vertical panel about 6 inches back from the headlight bowls, these earth the front lights on each side, can't think of anywhere else to check.

[Bugdisco]

I have similar symptoms. Will be checking all earths later today . Including the rear as I’ve recently converted to pickup truck meaning all rear wiring in the tub is now only protected by the metal covers .And water can definitely get  in .