1987 911, drivers headlight won't illuminate?

[ryguy0492]

Hello everyone, trying to figure out some electrical issues with my 87 carrera. For a while now, the headlights haven't been working. I fumbled around with the headlight switch under the dash, and by jiggling the solid red wire going to the headlight switch, the passenger headlight and corner lights illuminate. However I can't get the drivers side light to turn on.

The strange thing is, if I click the stalk forward, the high beams on both sides will illuminate, even the drivers bulb (there is only one bulb sharing high/low duty)

Any guesses? I've checked fuses

[Bob Kontak]

Low beam in the bulb is kaput at first blush.

[ryguy0492]

had a new bulb, tried that. Nope.

[timmy2]

turn signal switch quick fix pictures

[FrankM_]

Careful with that, the 'solid red wire' is unfused from the battery over the contact switch to the light switch ! And is 'ALWAYS HOT'
It should have a good solid contact on terminal 30 of the light switch (clean contacts), no 'jiggling' required.
The terminal 56 of the light switch provides power to fuse 3&4 (fusebox II) and runs the headlights.

Most plausible : check your fuses, left and right side are separately fused and separate fuses for normal and high/beam. It is fuse 1 to fuse 4 on the fusebox 2, 4 fuses of 8A in a row.
Fuse 3 runs the left headlight - blown fuse or bad fuse contact ?

If not that and you have replaced the bulbs : a wiring issue ? Do you have relays installed for the headlights and high beams (non standard but highly recommended) ?

[Ray 911s]

I have the same problem but on the right side. I checked the bulb on a regulated power supply - both high and low are functional. I also swapped the bulbs left to right. The problem stayed on the right side. Used a multimeter to check the leads. There is no power to the low beam wire on the right side. High beams are fine.

I have just installed the JWest relay system and nothing changed. Fuses in all four locations are good.

Reviewing the wiring diagram didn’t help - I am wondering if there is something in either the stalk or in the gauge lighting circuit that can impact the low beam. I can’t read the current path diagram well enough to know which terminals on the switches should have feed power. Getting ready to remove the stalk and the headlight switch to test all functions for shorts or dead spots.

In the meantime I lowered the headlight aim and drive with the high beams

[ryguy0492]

thanks frank, yes pin 30 (solid red) required jiggling, and if it did make a connection and illuminate the lights, the connection would get HOT. Now today, i wasn't able to get any of the low beams, orange side indicators or anything to illuminate, pin 30 wasn't getting hot either. I did use a voltmeter and checked and still had about 10v coming from the solid red wire.

I've been struggling with these lights for a while now, just ordered a light switch off ebay. 175 for a "good" used one. Hopefully that helps me

[FrankM_]

Ok,

Let me know. 175 is a good price for these switches, I asked at the dealer and they wanted 550 Eur !
One thing though : do install headlight and high beam relays to protect the (new) switch from the high currents (like the JWest kit). Using these, the switch should not get hot again as the main current is run through the relays.
It won’t solve any wiring problems you may have, but it protects the switch and in my case brightened up the headlights !

[timmy2]

The fuse panels have an internal jumper for the lights on the input side (top) and 2 fused outputs (bottom) to the lights. (Both low and high beam circuits have their own jumper)

If one side of the pair fails (say low beams) and both the fuses are good, I’d try swapping the low beam wires to see if that would move the problem.
If so, the jumper has failed. Replace the fuse panel segment or installing a jumper wire on top will fix it.
(actually I’d probably just temporarily jumper the correct top terminals first to see if the other light comes on)

[FrankM_]

@Ray911
Installing the relays won't fix that issue as you are mostly reusing all the wires that are in the car to switch the relays on/off, so if you have a problem there, it gets 'ported' to the new situation.

I like the idea of timmy2, I hadn't anticipated that the jumper/bridge could fail but it certainly can become loose or oxidated. As timmy said, use a short wire to make a temp jumper on the top of the 2 fuses and check.

If that doesn't fix it, jou will have to use an Ohm meter to check the wires running to your non-functioning light. Especially from fuse 4 (right light) a yellow wire (MY88) should run to the headlight. Measure it (power off) with an ohmmeter on both ends to see if the wire is uninterrupted. Then you know it is not the bulb, nor the wire running through it and it has to be fuse / bridge related (where left and right circuits split).

When checking the fuses, do get them out, clean the contacts and reseat them, do not only visually inspect them.

[ryguy0492]

thanks for the help gentlemen. Frank i will definitely let you know. I'd say 50/50 chance this switch actually functions correctly and solves my issues. Yeah everywhere else was 550 for a new switch.

I'm not the most well versed in wiring, is timmy talking about just taking a short wire and running it across the top contacts of the low beam fuses?

[timmy2]

Yes.

[FrankM_]

Just as a reference , post 3 in this thread is how I tested my light switch. I saved this picture on my PC just to have a reference to how the switch should behave.

https://forums.pelicanparts.com/porsche-911-technical-forum/1013955-need-headlight-switch-help.html

Mine checked out fine except for a few dead spots in the dimmer for the interior lights. Since I replaced them with LEDs I don't use the dimmer very often, they are onw minimum and still give ample illumination.

Also, I consider the following updates a necessity to the light circuit :
- headlight / high beam relays (don't run the power through the switch)
- fuse (3A) the interior light circuit / ashtray light ! Really - don't leave this unfused !

Other electrical changes done on my 85 Carrera for safety: footwell blower fuses (2x 10A), AC evap blower relay fused (15A), AC front condersor blower fused (7.5A).

[Ray 911s]

I am also going to put a fuse in the circuit for the dash illumination. I recently had an issue that burned out the rheostat (dimmer) and wrecked my light switch. Dash lamps are not connected until I find the cause, but it may have been a short inside one of the gauges. They’ve been rebuilt since then, but I will inspect the harness and install a fuse on the circuit before I connect it to power again.

[Ray 911s]

@Timmy2 - between your notes and the instructions for the headlight relay, I think that the yellow wire is right side low beams and the white wire is left side low beams. By switching these two wires, then, the problem should also switch to the other side? In my ‘77, the yellow wire is in fuse 6 and the white in fuse 8, so the right side must be controlled by locations 6&7, the left by fuses 8&9.

Before trying to jumper the two fuses (6&7) that control the right side, it might be better to try to disconnect white from 8 and connect yellow there to see if the right low beam illuminates. I don’t want to risk letting any smoke out of the harness.

[timmy2]

For illustration, As per the ‘77 schematic below, wires coming from the headlight switch: (56a and 56b)
Yellow is to the top fuse 6 for both low beams. Fuses 5&6 feed left and right low beams
White is to the top fuse 7 for both high beams. Fuses 7&8 feed left and right high beams

This configuration to feed left and right hi beams or low beams did not change from ‘64 to ‘89, and likely beyond.
The terminal designation may have moved for some year though.
Count from the headlight back.
I’m hoping this makes it clear not to mix up the yellow and white wires.
Notice the black line between the fuses on the top of S5 to S6? That is representative of the internal jumper.

[Ray 911s]

Oh, man. My harness is MESSED up! The blue and blue/white are hooked up to 5&6, and fed by the yellow wire from 56b. The yellow and green/yellow are on 7&8 and fed by the white wire from 56a. That wouldn’t be too bad if it just meant that the stalk positions were reversed. But, there are wires connect to the top of both 5&6 where there should only be a wire on the top of 6. I need to figure out what the extra top wire on fuse 5 is doing.

Sigh

[timmy2]

Post a picture.

[timmy2]

Here, this may help....
https://www.dropbox.com/sh/jxno8o6qae3roun/AADW1qBcRc53LoEG0TPbRwFva?dl=0

‘77 schematic

[Ray 911s]

Front of the car to the right of the photo. On the top, Green was yellow, blue was white (JWest instructions). Gray wire on top of 5 is a mystery.