headlight stuck in high-beam position
 

Background:
My headlights have been very flakey lately. Sometimes one or both are very dim, and sometimes they're out completely. When one is out, I've managed to hit it and the light came back on (so I figured the wiring is loose), however, when it's dim, I'm not able to do that.

Now:
I turned on my car and the headlights today and noticed that the headlights were stuck in the high beam position, and my headlights are out completely. It's pitch black and late, so I haven't checked whether the bulbs are out or not.

I have, however, checked the dimmer relay as per the FSM (Body and Electrical T-51. I hooked up the relay to a positive and negative source, then checked the R/B and R/G connectors, and there was no current running through those. I yanked out the dimmer relay off my parts car (which I knew had working headlights), and did the same test and got the same results, no current! Am I doing it wrong? Or missing something?

I tested the harness that connects to the relay, and when I have the headlights on, the R/B and R/G connectors have current running through those (so I can rule out faulty wiring, right?)

So my questions are:

1) I know for a fact that the second dimmer relay I have is working and it failed the FSM test, so is it possible I'm doing the test wrong? I have the W wire hooked up to the negative terminal on the battery, the wire above the W wire hooked up to the positive terminal on the battery, the R/B hooked up to the red connector on my voltmeter and the R/G connector hooked up to the black connector on my voltmeter.

2) Do you think the dimmer switch could be the culprit? I haven't yet looked at that

3) Could either of these problems have been the cause of my headlights dimming and going out?

possible a ground problem.................check your grounds/corrosion in the connectors.

hmmm, that's a good point, i should check those, does anyone know where the ground locations for dimmer relay on an S5 NA?

heres a diagram of the wires for the headlights

thanks for the diagram jgrts20, however, it doens't really show me where exactly the ground locations are. I guess I'll just have to follow the wires and find them.

sorry I tried, just check the wires that arent on the diagram*shrugs*

I had a problem like yours not too long ago, it turned out there was rust on the inside of the switch (i have no idea how) and it was blown. If they keep the brights on after you run the wires then replace the switch, I used one out of a '91 Ford Probe.

I'm thinking it might be a bad solder joint or something, I'll know when I take the switch apart tonight. I'll let you guys know

Well, it started working again on it's own.

But I took apart the switch anyways. I didn't find any bad solder joints

I regrounded one of the grounds points while I was at it, right now it seems to work ok, with no dimming.

We'll see...

it worked for a week, now it's stuck in the highbeam position again.

I suspect that the problem will fix itself again.

Any idea why this is happening? I've checked the relays and the switch and didn't see anything that might affect it.

If it is in fact wiring, how would I check this, and how could it make the switch stuck in highbeam position and not allow my headlights to work

Any ideas guys?

buy a new headlight relay, more then likely thats your problem.

Sounds odd that it would happen to BOTH lights, but I was having problems with ONE of my lights on my 86. For a while it would only work in high beam mode. Then it stopped working at all. It was just really dim. So I went ahead and purchased a new set of lights.

On installing the new lights, I found that the plug was in horrible shape right where the wires met up with the black plastic. From the lights going up and down, it completely destroyed the wiring. I had to crimp everything back together, but now my lights have to stay in the up position, so that they don't destroy it again, until I can take the time to fix it properly. So, the old light was still good, my wiring was just completely screwed.

I woul think that too, but I've swapped in a definitely working relay with no luck.

My last guess would be something in the wiring. Bad grounds would not cause this problem would it? I could see it causing the lights to be dim or going out, but I don't see it making the highbeams stay on.

ok, i'm gonna pull out the switch tonight and check the continuity of some of the wires. I'm thinking perhaps the wire that controls the highbeams from the switch is getting power when it's not supposed to. Does anyone know which colour wire to check for this? I couldn't find it in the FSM, or if it's in there, can anyone let me know which page/chapter to look at?

Your trying to solve a no dimming of the lights when you toggle the dimmer switch??????

The way I see it when looking at the DIMMER SWITCH in the jpg, is the LATCH CCT is powered by the RG wire coming from the HEADLIGHT RELAY. The ground for the LATCH CCT is from a ground located behind the combination meter inside the car.

When you pull the DIMMER SWITCH, you MAKE the contact shown in the Dimmer Switch. The contact that is shown OPEN in the picture. It seems when you do that that the LATCH CCT outputs a ground to the WHITE WIRE on the Dimmer Relay to make the headlights go from dim to bright and vice versa.

Actually I don't quite understand that set of contacts in the Dimmer Switch because there is already a gnd at the Latch CCT coming from gnd number 10 and when you make that contact in the Dimmer Switch your just adding another gnd to the Latch CCT from the RW wire. I don't get that part. I just understand that when you MAKE that switch you put a gnd on the white wire of the Dimmer Relay to make the lights go high/low beam. EDIT: OH, I understand that contact now. That is for when the headlights are off and you pull the dimmer switch back to make the headlights come on. It puts a gnd on the HEADLIGHT relay to pull it in so the headlights come on.

I'd put everything back together except the DIMMER RELAY which I'd leave the plug off it. I'd put a meter to the WHITE wire and the other meter lead to the battery neg terminal. Put the meter on ohms, then pull the dimmer switch back and forth. The ground on the white wire should come and go when you do that. If it does come and go, and you have 12v on the RG wire of the Dimmer RElay, then go buy a working Dimmer Relay.

I recently replaced my dimmer switch on one of my cars. It would not stay LATCHED. New/used dimmer switch solved the latch problem.

Thanks for the explanation Hailers, I think I've verified that the dimmer relay is working yesterday, and I think I've found the problem.

I pulled out the headlights to find that on the harness that plugs into my headlights, the ground wire connection had melted some of the plastic on the harness and the connector in the harness was all rusted and corroded.

I would've check this connection sooner, but I thought it was weird that both headlights were dimming or going out. It seems that the main ground was bad, it had grime all over it from a leaking brake fluid cylinder that I had. Could that have caused the ground wire connections at the harness to melt the harness and rust like that?

Also, another thing I noticed that was weird was, when both lights were out, I wiggled the connector around and got the light to come on, both lights would come off. If I pulled the harness off one, and the other headlight would go out with it. Why is it that it needs power to both lights at once? From what I can tell in the wiring diagram, it shouldn't act this way.

It should npt.

I was going to ask you to use that switch in the car the operates ONLY the up/down function of the headlights, and have the headlights UP.

Then have you pull on the dimmer switch to see if the lights came on when you did that.

The only explanation I can give for both lights going out after you wiggled one connector and then both lights went off.......is that the contacts in the dimmer relay won't carry the current demanded of both lights???? Yes. OR, in my manual for a 87, it shows the ground for both light is actually from the ground block just below the Trai Coil area. I'll post a picture of that if you don't have one.

I'm sort or arguing that the ground near the headlight motors is not for the headlights themselves. Any body care to input about that????? IF that ground near the headlights is not for the lights, then what? FSM could be wrong. If I jpg it won't be til tomorrow.

The headlight ground is supposed to be GROUND NUMBER 5 on a series four 86-87 model, under the trail coil area..