Right side parking / rear lights out

jrl · 03-29-2006, 05:48 PM

Tonight I noticed the right parking lights were out, front and rear ('86 930). The fuse for the right parking lights is good but voltage doesn't get to it when the light switch is turned on. Voltage does get to the left parking light fuse with the switch on. Headlights/turn signals ok. Barring a loose connection, most likely culprit is the headlight switch?

John

ruf-porsche · ruf-porsche's Garage

Nope, most likely a loose connection in the harness. Either that or the bulb is shot.

CarreraS2 · 03-29-2006, 06:35 PM

'86 carreras have an odd diode that one side of the parking light circuit runs through. The diode is in a little holder under the dash, close to the wiring for the headlight switch. Was a weird thing - only one side, and only '86. No one seems to know why. But when the diode dies, the front and rear parking lights on one side die.

Your turbo may have the same thing. Although as I recall it controlled the left (driver's side).

do a search using "diode" "carrera" and "lights" (or something like that) and you should find some info on it.

I also had a parking light problem like that once in an '87, it turned out to be a bad turn signal switch.

javadog · 03-30-2006, 03:05 AM

I have an '86 930 that had the problem with the diode. In my case, it affected the lights in the right rear. We replaced it with part number 911.617.108.00.

JR

jrl · 03-30-2006, 04:59 AM

Really appreciate the info -- I saw the diode under the dash last night with the right-side wire feeding it. Agreed, it's an odd place to use a diode. The plastic case appeared a bit melted around it, but tonight I'll get it out and check with a mulitmeter.

charleskieffner · 03-30-2006, 05:04 AM

tell me what you find have same problem w/left side running lights. brakes/turns work but no running lights

jrl · 03-30-2006, 05:15 AM

Will do. I'm an EE and can't figure what its function would be. Since it was one year maybe it was a patch for an oddball issue. Anyone know?

jrl · 03-31-2006, 05:06 AM

Update - Last night I pulled the diode out. P/N is as above, and it's a black 0.25 x 1.0 spade-lugged case that's attached by an odd arrangement of clear plastic connectors (never knew Rube Goldberg worked at Porsche).

I checked it with the diode function on my multimeter, and sure enough, it was failed open. If you don't have a diode function, check resistance with the +/- leads connected in the direction of the diode arrow symbol; if it's failed, resistance will be in the neighborhood of 1 megohm. Reverse resistance must always be very high.

It's hard to understand why this sits in-line with the rightside side lights; about all it does is put a 0.7 volt drop on the line. On a hunch I reconnected the line without the diode, and the right lights came on, no melting/smell or signs of problems. However, being paranoid about Porsche electricals, I'm ordering a diode.

The reason these things fail, I'd guess, is that they heat up, and over time the diode opens up. I tried to measure the current pulled by the right-side bulbs but couldn't get a good number.

charleskieffner · 03-31-2006, 06:00 AM

after speaking w/my mechanic he stated my 3rd eye brake light and my left side running lights (2) are in line w/one another. i mentioned your diode and he looked at me funny and asked how i knew? i told him i have the manual and left it at that................it was precious! thanks

Pipo · 04-15-2006, 04:45 PM

Can somebody tell me where exactly this diode is? I am looking under the dash around the steering column but I can not see the darn thing. I already bought the part from the host but nothing looks like it. I also looked under and around the radio area. My right (passenger) front turn signal is not working, I change the bulb check the housing and the fuse, and this is my last hope before I go to my local Porsche repair shop, $100 an hour ouch! Thanks.

jrl · 04-17-2006, 07:02 AM

The diode holder is an in-line plastic holder. Maybe I was lucky, but it was nearly dangling down at the column under the dash. My right turn signal wasn't affected by the problem nor the stop light, only the right front/rear parking lights. Good luck.

brday · 04-17-2006, 06:30 PM

Just had (and solved) same problem. Ordered the above referenced part number from our hosts. My diode was located about 3 inches up the line from the master headlight switch. If you are facing the dash, the wire for the right side marker lights is at about 5 O'Clock on the switch. Follow this wire and you should find the diode. It is encased in a 2" plastic case. I bypassed the diode for a temporary solution while I waited for the new part, but was nervous the whole time. It is a bizarre part, but someone put it there for some reason back in '86!

Anybody see the release notes???