Indicators don't work when headlights are on ?!! Help

[mrob71]

Hi there all.. Help please....... I have a T25 1984 model... and though it's a very sound car.. it has failed it's MOT today due to electrical faults with the lights. The indicators and hazard lights work perfectly fine, but when I put the headlights switch on( dip or full).. then the hazard lights and indicator lights stop working...!?
'Ive only just bought the campervan.. so any help, advice and guidance would be great.!! .( ATS could not help with this when they failed the fan)
We're trying to avoid high garage costs and would like to try and resolve this problem ourselves.. if at all possible.. xxxxx

[clift_d]

First thing to check is for a bad earth.

Behind the fuse box on the left side of the van there are a couple of earth crowns fixed underneath the dash on the a-pillar to the body of the van - you need to undo the screws holding the fuse box in place and gently push it out of the way in order to be able to see them. You shouldn't need to unplg anything form the fuse board to do this.

What happens is that the contacts on the earth crowns corrode over time leading to issues similar to what you're suffering. Carefully pull all the connectors off the earth crowns - maybe bundle them together in a clothes peg so that you don't lose any - then get a small bit of sandpaper and clean off all the tabs on the earth crowns and replug your various wires one at a time.

Hopefully your problem should be solved.

[clift_d]

Earth crowns

[marlinowner]

Yes this sounds very much like a problem at the earth crowns, I suspect it is a bad contact between the earth crown itself and the van body. If that earth connection is lost then the indicators/hazards can find a route to earth through the headlight/sidelight bulbs and the rear lights to the earth at the back. That route is lost when the lights are turned on.

You could test for that by using a battery jump lead or similar to connect the earth crown to a suitable point on the van.

[mrob71]

Oh my goodness.. thank you so much for taking the time to post the messages with your great advice.. and not too technical for this Welsh bird to understand!
I will get hubby on to it tomorrow and will post a message to explain how it all went.
Only the other day we were told by a garage that we needed new parts to the exhaust pipe( because of holes)... and were quoted £375. After picking myself up from passing out... hubby insisted he would have a go himself( complete novice). and bought some gungun and tape from halfords..£10.. and managed to cement it up. Unsure if it had stopped all emission leaks.. we took it for it's MOT today.. and the emissions were fine .. so a massive saving there( for now at least!) Money saved will go nicely towards a 2nd hand awning I guess! So I just need to get some new windscreen wipers and fix the electrics.. and we're good to go for our summer trips!... Thanks again... so appreciate your help. xxx

[CovKid]

Home Bargains do the best windscreen wipers I've ever come across - not like the flimsy Bosch ones and half the price. They last a year or more easy.

[mrob71]

Thanks Covkid for that handy hint.. will check it out tomorrow, hope they have my size there..!

[mrob71]

UPDATE: We have checked the Earth terminals with a tester
and one of them at first gave 20% of resistence.. but after applying wd40 it gave 100%..( so they seem fine)
BUT from the 11th fuse there is a blue cable going nowhere ( not connected to nothing ?! ) We thought this could be earthed.. so we connected to earth with a jump lead and it blew the fuse. We realized that fuse had something to do with the indicators.., as after it blew, the indicators didn't work at all... but hazard lights were fine. We have replaced the fuse, and indicators are now working again.( but not when headlights are on)
Where should this blue cable go to ?

[keytouch]

Quick question, have you been out of the van to check the indicators don't come on with headlights? Just checking it's not just the telltale led.

[tonytech]

Resistance is measured in ohms not %.
if you have an old style analogue meter, touch the probes together to check where the zero is on the scale (most meters have zero at the far right of the scale)
The resistance between the earth crown and the chassis should be as close to zero as possible.
WD40 really shouldnt make any difference. It disperses water not miracles.
Fuse 11 (I think) is wipers, do they work if you remove the fuse.

As said above earth crowns can cause allsorts of weirdness.

T

[Smcknighty]

I was going to recommend contact cleaner for the earths then found this

http://www.screwfix.com/p/wd-40-special ... 00ml/92716" onclick="window.open(this.href);return false;

Wd40 contact cleaner, who'd have thought!

I'd say leave the stray blue wire alone - it's something someone added by the sounds of things.

Good luck!

[tonytech]

Contact cleaner is fine for switches and the like that cant be taken apart. It cleans dirt and carbon deposits off.
For earth crowns, as said above, take them apart and scrub with sandpaper or emery cloth.
T

[mrob71]

Hi all...
Yes, we have checked that indicators are not working by looking from outside the van.....
Thanks again for handy tips. We'll give it a go......it's such a spaghetti junction of cables behind the dash it's scary! and almost impossible to move the fuse box as the cables are v. tight to it.... Thank you / diolch .

[keytouch]

Last couple of questions from me,
Does the indicator tell-tale led do anything when you put indicators on in any circumstances? (With or without rad lights)
Same question about tell-tale led when hazard switch is pressed.

[mrob71]

UPDATE.. Happy to post that the indicator lights are now working perfectly with and without headlight being on... Great news..Again, thank you all.
It was the earth all along..
Just bought new windscreen wipers from Home bargains( as suggested by someone.. £2.99).
Fit is ok.. but somehow the wipers are behaving irrationally... few seconds ok, then they go beyond the screen and continue down onto the vans body..! Had my MOT retest booked at 3pm today.. but I might have to cancel... Any suggestions please?