Trueno headlight issue ...

[eight-six]

Finally put my car back together and its almost complete. Annoyingly though I have an issue with the headlights.

I dont have any dipped beam, only main beam and flash. The blue main beam indicator light is on permanently on the dash as well.

I have checked the bulbs, fuses and relays and all seems to be in order. I have also checked the power with a multimeter and compared it to a mates car and I seem to be gettign some odd readings - it seems that I am getting 3 12v power feeds to each headlight which surley cannot be right.

Thing is I cant understand why this is happening as nothing has been rewired, I have just connected the cars loom up as it was previously.

Can anyone help?

Can anyone also tell me where the earth for the headlights is etc?

The car is a Trueno in case it makes any difference?

Desperate to get the lights fixed so I can use the flipping car.

Cheers

James

[Ivan141]

If you havent changed anything, I would first check the grounds and recheck all the connectors. The grounds on the AE86 headlights are actually routed back to the switches (switch is in the ground side of the circuit). Maybe you got something backwards?

[eight-six]

Quote:If you havent changed anything, I would first check the grounds and recheck all the connectors. The grounds on the AE86 headlights are actually routed back to the switches (switch is in the ground side of the circuit). Maybe you got something backwards?

So the earth for the light goes back to the switch, and then goes from the switch to the earth. Does the earth for the switch earth out on the small fuse and relay unit in the drivers (RHD car) footwell.

I don’t know if it makes any difference but items like stereo, AC unit, heaters, blower etc have all be removed so the wiring loom doesn’t connect up under the dash like it would if all these items were still installed. Could that cause an issue?

Sorry if that sounds daft, I have tried everything and I know its notoriously difficult to diagnose electrical through a forum so I just think its best to throw everything out there just in case something clicks in some ones mind.

[Ivan141]

I think the fuses are always on the 12v side of the circuit, usually not too far from the battery, so that's the wrong place to look..

So lets assume the bulb is getting power, then all that is needed to switch on the low beam is a connection to ground though the switch. The high beam indicator is wired after the low beam coil, parallel to the switch.
When you power the lights on, the headlight relay closes and both coils of the bulb get 12v. This can only happen if you turned on the low or high beam.
When the high beam is grounded through the switch, current can flow and the bulb will light up. The low beam coil also sees 12v but will not light up because no large current can flow. However, the little current that does go trough powers the high beam indicator in the dash.
Now when you turn on the low beam, the switch grounds that side of the circuit, and the high beam indicator is effectively grounded on both sides so it should turn off, whilst the low beam coil now has a good path to ground and current can flow.

What this means in your case: Your high beam indicator is working, this means current is getting through at least one low beam coil. Your high beam and flash work, these go to the same ground as the low beam.
I'm inclined to think something is wrong with the switch.

[Ivan141]

Just had another look.. if it's not the switch, then you are missing a wire from the switch to the bulb, it's supposed to be on a 12-pin connector, around the bottom, middle of the connector. Check for continuity between the bulb and the switch when the low beam is switched on. it's a red-green wire by the way. Now go tackle that problem!

[F0Bman]

Wow you are really good!

[Ivan141]

I would feel betterabout it if eight-six solves the problem, no news yet though.

[eight-six]

Hey Ivan,

Still no luck, turns out I also dont have wipers or washers either - stupidly I didnt check before hand. Going to try 2 replacment switches to see if thats the cause, if not the dashboard will come out so I can trace the cables properly and check whats going on.

Wont be able to look at it properly until the weekend - if I am lucky.

[eight-six]

Crap ... 5 months on and its still not fixed - to be fair I have been sorting other problems so havent really been looking at it.

I can only conclude that its not a wiring issue - no fuses are blown, and everything is connected properly.

Ned to start doing checks to make sure that the various boxes etc are all working properly.

If a relay is duff could this cause the issue? The headlights have a 3 pin relay which I need to check - could a duff relay give me mains but not dipped?

Now the engine is in an running I wanna get the headlights done - gets dark so early now I dont want to be caught short if I take the car out.

[Ivan141]

Nope, the only relay that's important for the lights is in working order cause your bulbs are getting power.

Check the switch, it's your most likely culprit.
Measure continuity between the red-green wire i was talking about earlier and one of the white/black grounds with the switch set to low beam.