Headlights won't turn on--please help!

[PorscheNut924]

I finally got in and replaced my temperature switch so I don't have to disconnect my battery every time I park the car for more than a few hours due to radiator fans not turning off. That went well.

Until I tried to drive it afterwards and discovered that while my headlights do raise just fine, and all the other lights work, there is no light coming out of my headlights. I checked the fuses. Fine. I checked the bulbs. Fine. I even tried new bulbs. Nothing.

The only things that happened that involved the headlights during that process were:

1) I left them raised so the gear would get out of the way and I could reach the temperature switch.

2) After I turned them on, I disconnected the battery, and accidentally crossed the wires, causing sparks for a split second. I figured this must have blown the bulbs or the fuses, but neither of those things are broken.

3) When I disconnected the radiator hose, some of the coolant that came out splashed in the direction of the headlight wires. At this time, though, the battery was disconnected.

I have no idea what to try next and I really need my headlights to work!

[rhett]

Electrical gremlins...they like Porsches! Your step 2 "After I turned them on, I disconnected the battery, and accidently crossed the wires.." Which wires are we talking about? The battery wires or the headlight connection wires? If you caused a spark at the battery that would probably not damage anything as you just took the supply to ground. If you sparked at the headlight..that is different and would have taken out a fuse or two. One thing it could be is a broken wire in the headlight loom, years of going up and down causes the wires to break..then any movement in the loom will cause an open circuit. As it is both headlights, I would suspect a ground (brown) wire, I think they are commoned across both headlights.

If you have a voltmeter you need to check that 12V is getting to the bulb connector, and if you have an ohmmeter, check continuity between the ground for the headlight bulb and the chassis.

Did you move the wiring at all when you were working on the rad, even when you cleaned up the coolant spill?

[PorscheNut924]

Well, I found the problem. And it was sort of my fault. Before I replaced the temperature switch I'd taken the steering wheel off to clean the windshield wiper and turn signal switches, since they've been acting up for a while. I didn't get the wires to the high-beam switch plugged in correctly. It just occurred to me when I realized my brights weren't working that perhaps the wiring for the headlights goes through that switch. Haha.

All fine. But while I'm here, I might as well ask about a related issue I've just been ignoring. The driver's side high beam won't come on. Bulb is good, and I've tried other bulbs, and they're all the same. I checked the fuses, sanded the ends and the contacts, and still no good. What in the world could THAT be?

Anyway, I've got my headlights back and other repairs continue...

[Gawernator]

Glad you figured it out

[rhett]

Yep..glad you got your heads working. The high beam problem should be quite simple. A single relay operates both lights, so as one comes on the fuse and relay must be OK. The 12V feed from the relay goes to one light and then over to the other, so it could be a break in the cable. The ground connection in the faulty light could be bad. If you can get hold of a multimeter or AVO, check the continuity to ground (chassis) and the between the lights for the 12V feed (don't have the lights on when you do these checks or you could fry your meter! - always pull the fuse). BTW, does your marker light on the bad side work properly, as that shares a common ground with the high beam, according to the wiring diagram.

[pup]

Headlights go up and down, high beams flash, but no low beams. They were intermittent for a while, then disappeared entirely. Fuses all look OK. Is there a relay for low beams? What else should I look at?

[fiily]

Check your wiring where the headlight plug cables run down along with frame, they frey and you might have to cut back the plastic/shrink wrap to see the snapped wiring.

My highbeams didn't work initially and after changing the bulbs, I traced the wires back about 7-8 inches and cut the heatshrink back and found 2-3 wires just snapped in half.

Once I fixed the wiring there, all is working great again high and lowbeams.

[944 Ecology]

Originally Posted by pup

Headlights go up and down, high beams flash, but no low beams. They were intermittent for a while, then disappeared entirely. Fuses all look OK. Is there a relay for low beams? What else should I look at?

If you have an early 944, based on the 924 chassis, the fuses can look good, but may have too much resistance as a result of corrosion. Remove the fuses, clean the ends with a wire brush and try them again.

[DannoXYZ]

Yes, never just look at the fuses. Pull them out and measure resistance with voltmeter.

In troubleshooting the hesdlights, best to use voltmeter and trace path of wiring:

1. Do you have +12v going into headlight switch?
2. Do you have +12v coming out of headlight switch when it's turned to ON?
3. Do you have +12v coming out of each headlight socket?

Same with high-beams:

1. Do you have +12v going to highbeam switch?
2. Do you have +12v coming out of highbeam switch when activated?
3. Do you have +12v going to highbeam relay?
4. Do you have +12v from highbeam switch to relay?
5. Do you have +12v coming out of relay when activated?
6. Do you have +12v at each headlight socket on highbeam terminal?

In this case, there's a broken wire somewhere between the relay and the highbeam that's not working. You can actually probe the wire with sewing needles to find where the break is. Most likely it's behind the headlight in the section that gets flexed when the headlight goes up and down.

[Jfrahm]

The connector at the bulb is often a problem, or the switch itself. If the bulb wattage is increased the wring or relay could be damaged too.

[djnolan]

If it is both lights, then it is something common like the relay or switch or the fuse. What year and model of car?

[coneyislanddon]

I use methanol to clean the inside of the lens out. When i was done poured it out and let it dried, then i put both headlights back in the car and connected them. my low beam lights are not coming on but the high beams are working and the dipped beam movements are working well but i keep getting these message about the headlight. i changed both low beam lights and the problem is still there. Does anyone know the reason?

[DannoXYZ]

Follow all the troubleshooting steps listed above and you will find the problem.