InC

Hi Guys,

Does anybody know where the head light relay is? Both the head lights are not working, only the pilot lights are on. Any idea what could be the problem?

It Is a stock 88' Turbo i reckon its similar to 911s
Thanks.

3.2SLANTNOSE

This might sound like a smart *** answer, but, is the ignition on when you are trying the headlights?

justinsrx7

Unless you have an aftermarket relay, my understanding is that there is no relay in the headlight circuit which is why the light switch gets damaged over time. The result of that though is that the brights and dims stay on together, not that both lights don't work (or at least that is my understanding and experience). If there was an aftermarket relay, people typically install them underneath the fuse box which is where I added mine.

Stupid question, but if both lights were working fine before, is it possible that both bulbs are just coincidentally burnt out?

dshepp806

Fuses OK?

scottb

Fuse?

3.2SLANTNOSE

Yup, left and right side headlight fuses. I am still waiting to see what happens when he starts the engine, then try the headlights?

BlackPearl

Make sure the key-switch is all the way on or the engine is runing. Check the fuses first.

For your sake, I'm hoping your headlight and dimmer switches are okay. But ... here's a quick low-down.

I upgraded to H4-Euro headlights on my '83 SC. The guys I know who work on 911's told me to set up a remote relay system BEFORE I burn out the swithes on the dash/steering column with the more-powerful H4's ... which I did.

After buying all the hardware, I looked up the wiring diagram in the service manual I have (Bentley). Sure enough, no headlight relays. A quick review of the wiring diagram indicates the current for headlights runs from the battery to key switch; to dash switch; to dimmer switch; back to fuse panel and out to the lights. WOW! All that current runs thru the ignition/dash/dimmer switch without a fusable link, and THEN is fuse-linked from dash switches to the lights. Now, I looked at the contacts for the light switch and the dimmer switch: itty-bitty!! Not good for high amps.

So: I re-routed the lead from the switches to 2 X 30-amp relays; one for low beam and one for high beam. Now, the maximum current through the dash/dimmer contacts is no more than 15-amps. AND, the link between switches and 30-amp relays is fused with a 15-amp fuse. Also, the lines from the 30-amp relays to the lights (both low and high beam) are linked with a 20-amp fuses... stronger than needed, but a good safety fuse.

The Itty-Bitty contacts in the light/dimmer switches are prone to burning out over time. This appears to be so with all 1960's, 1970's and 1980's 911's. I don't know about the 1990's and later cars.

So, long story short (sorry for that pun), you might have lost the switches in the dash. First check fuses #5 thru #8 in your fuse-bank. Then check further down the flow-line of the fuse-bank/ignition switch/light switch/dimmer switch line. If the fuses are all intact, it could be one of the switches ... a bit more complicated to fix. Often the dimmer switch goes before the on/off light switch.

All those who read this: it's my personal recommendation that ALL 911 owners install relays for their headlights BEFORE they burn out their switches. You can get two relays for about $25.00. The Bentley Manual or Porsche Service manuals have very accurate wiring diagrams, and in about 1 hour, you'll have a more fail-safe curcuit for your headlights. This, of course, is my personal opinion.

One more thing: with relays installed, your lights ... even the stock ones ... will be about 10% brighter!

Hope that helps.

InC

Thanks Black Pearl. It sounds like the head light switch might be blown. any other ways I can test the switch? All conditions were satisfied, key on, car running.... fuses both okay. so that leaves the bulbs and the switch.

3.2SLANTNOSE

Hi, I would advise you to do just a couple more test. When you checked the fuses, did you check with a meter or test light to see if there was any voltage on both sides of the fuses, or did you just look at them and see that they were still intact? If there was voltage, on to the next step. It does not happen very often, but I have seen both headlights blow, from a voltage spike, or even just by chance that they both had burnt out. If you have a test light or meter, turn everything on, car running headlights on, etc. Then actually check to see if you are getting voltage to the headlight connectors, by either a test light, voltmeter, or another headlamp. Do this simple test to just be sure, before starting on a switch, and then the lights still not work because they were both burnt out. I actually had this happen to me in my new 1979 VW, about 3 years of ownership. That was the only time it has ever happened to me personally, but I do know of it happening to other peoples cars that I have serviced in the past. Good luck!! Tony.

BlackPearl

3.2slantnose is right. Try checking the white and yellow wires above fuses 5 thru 8 (one is yellow - low beam ... one is white - high beam) with a voltmeter or a testlight with the key all the way on or the car running. If the wires on the top of the fuse bank above 5 thru 8 aren't receiving current, THEN start thinking about switches.

And, I too have heard about voltage spikes killing older headlamps. Rare, but it can happen. BTW: How's the voltage regulator performing?

ron mcatee

Please check the bulbs. This happened to me and I found both had blown at the same time. That's why I carry spares.

justinsrx7

+1 on the bulbs

InC

thanks for all the inputs... everybody!

SM Racing

My money is on Bulbs.


that old k.i.s.s. theory.

jakeflyer

BLACK PEARL-------------- Great information. Sounds like an hour of preventive labor and not much money is good insurance. This will be a print out into the Bentley book as a "to do". thanks