Electrical issue with lights and blown fuse
 

Hi,

Here is what is happening.

With the headlights switched on low:
The following happens:
Driver side running lights don't work on the front or rear
License plate lights don't work

With the high beams on:
Driver side head light doesn't work
Driver side running lights don't work on the front or rear
License plate lights don't work

Fuse 5 blows (fog lights?) i think when i turn the lights on. Fog lights don't work either.

Blinkers work, flashers work.

What do you think?

Ace

Do you need more info?

Can't see the year of your car on my phone. Do you have a headlight relay kit installed?
Have you removed and cleaned all fuses and terminals?
Do you have a test light or ohmmeter?

Timmy2 is basically saying what everyone else will say. You can either do it yourself or pay someone to find the wiring problem. Probably the fault is in the fuse panel in the left front of the car. You need to pull, clean and reinstall each fuse in the panel. Check the connection, at each end of each fuse, to see that it is tight and not corroded. Eventually, each little problem you describe will be revealed, one connection at a time. It is tedious. It helps to have a friend to keep you company while you do this. A test light usually is easiest to use but a volt meter can help you find the problems too.

OK,
On my laptop now and can see you have a 1987 Carrera.
Remove the fuse that blows and on the bottom side of the fuse holder check from it to ground for a direct short.
You have something that is wreaking havoc on the lighting wiring circuits, usually traceable to a short or bad grounds.
Have you replaced any lamps lately?
Do you have a factory manual or Bently with the wiring diagrams.
Do a little reading on electrical troubleshooting, do some cleaning and testing, then report what you have found in each of the troubled circuits.

I did a bunch of reading the last couple of days on here and there was a ton of useful stuff. Almost too much stuff. I'll start with what you have said so far.

Here are the answers to your questions:

I don't have a headlight relay kit installed.
I just learned how to clean the connections and will do that to the fuses and report back.
I have an ohm meter somewhere around here or I will find/buy one.
I'll check for the short on the blown fuse.
I don't have a Bently with wiring. (I'm thinking of breaking out the $$ for one though)

Thanks!
Ace

Oh yeah, I haven't put in any new lights lately.

The car has been sitting around for a few months without me driving it though.

Ace123,

You may want to check your engine compartment light switch for a short or burnt/bad wiring. It ties into the driver's side lights, and I've had a similar issue in the past that was caused by this. I solved it by replacing the switch and cleaning up all the wires and contacts.

OK,
Went through all the fuses and cleaned them up with the dremmel and made them shine. I also added a tiny bit of the dielectric grease to each one.

I'm getting the same results. When I turn on the lights I blow the fuse which is the fourth one from the front of the car.

I also checked the engine compartment and the light in there doesn't work although the bulb visually appears to be OK. I pulled the bulb and then tried it again and the same results happened.

Lastly, I checked the amperage from the bottom of the blown fuse to the neg cable of the battery while the lights were on and got .1 microamps.

Thoughts?

I found a wiring diagram in this link http://forums.pelicanparts.com/porsche-911-technical-forum/619742-1987-911-headlight-wiring-issue.html

Fuse 5 blows when I turn on the headlights. So when I look at the diagram , it shows the left head light and the left running lights as part of the circuit. The running lights are out. So do I check if there are shorts there? How do I check that?

Ace

Remove the fuse, connect one probe of your meter to the bottom fuse holder, the other to the nearest body ground nearby or the negative terminal of the battery. Turn the meter on to read ohms. What do you get?

Probably zero ohms which means you have a shorted wire somewhere or a shorted bulb in the socket.
Remove the running lamp cover and pull the bulb, then check the meter again.
Take a look under the bumper at the wires leading into the lamp housing and follow them as best you can. You may have a pinched or abraded wire.
You need to separate out the wires and test them to ground.
You have a dead short to ground and need to find it.

Should I do that with the lights on which is what produces the blown fuse?

No, the ohmmeter won't like power to it. You could blow a fuse in the meter. Pull the #5 fuse and test the wiring to see where it is grounding out.
Maybe it is as simple as a 2 pin bulb in a one pin socket in the running light housing.

Think of the electricity flowing like a recirculating hose system with water in it. It starts at the bottom of the fuse in that circuit, flows through the lamp where some is consumed to create the light and the rest goes back to the battery.
You have a leak somewhere and you are trying to find it by putting a little power from the meter through the circuit to see how much of a leak you have.
Perhaps you should google automotive electrical troubleshooting and try to learn some of the basic principles.
The danger factor is high and no one on this board wants to see anyone get hurt.

I just checked from the bottom of fuse 5 to the neg battery terminal with no keys in the ignition and it pulled 15 ohms. With key in and turned, but car not on, it pulled 47.5 ohms.

Thoughts?

Also, I did some research last night on the Internet as well. I'm trying to learn as much as possible. I'm getting better at understanding the wiring diagrams as well.

With the bulb out and key out it pulls 12.6 ohms

I swapped the running light and blinker lights and it worked the same so the lights are good.