shcuck

hey there, I need some help here. The "tail" fuse keeps blowing on me. When I pull the healight switch to the first step, so I can use the foglights and the markers, the "tail" fuse blows. This does not happen all the time, it seems to be random. Normally if the foglight switch is off and I pull the headlight switch, the fuse does not blow. Today, I was trying to fix my 3rd light, because it keeps blowing the bulbs, so I checked the voltage to the 3rd light. with the engine off and you put your foot on the brake, it reads 11.68 volts. If I turn on the car and with the brake not engaged it reads 4.6 volts, and with the car on and the brake engaged, it reads 13.8 volts. I dont know if this variance in voltage is normal, or is that one of my problems? Also, when I had the 3rd light disassembled, and I tried to turn on the foglights, the fuse would blow. I tried with a 10, 15 and 20 Amp fuse, and it blew them all. After I reassembled the 3rd light, I used a 10A fuse with the foglight switch off, and pulled the headlight switch, and no blow out. With the switch pulled I turned on the foglight switch and still no problem.

So here is where I am confused. Is the problem with the 3rd light, the foglights, foglight switch, headlight switch or all in general?

I do not know where to start trouble shoting. Any help would be appreciated.

Oh and sorry for the long story. I just wanted to explain everything.

Thanks
Shcuck

jfb

Your voltage measurements are all normal. Your biggest problem is that you have an intermittent short circuit. From your symptoms, I would inspect the wires going to the foglights. You should be looking for worn insulation allowing bare copper showing. Also, I have seen broken foglights from inadvertant front end taps and this can expose and bend the wires in the lamp (ie broken lamp) to short. Are both foglights lit when they do work? If not, the unlit one may be broken.

shcuck

JFB,
Thanks for the reply. Yes, both lamps work fine. Now when you say to check the wiring that goes to the foglamps, are the wires exposed, or how do I check the entire wire flow?

jfb

In my 87 electrical manual, it shows a purple wire from the fog light switch going to the 42 pin connector on the firewall in front of the brake pedal, then on the engine side of this connector, two purple wires go to each fog lamp ( one to each lamp). Now the wires will go through a split cable tubing (black) and a short there is unlikely.
The wires will break out of this tubing and go to each lamp socket and this is where you should look for a wire rubbing on something that is grounded. Also look in the dash from the fog light switch down to the 42 pin connector. The purple (may be a different color in your car)wire may be rubbing against something under the dash on its way to the connector.

shcuck

Thanks a lot JFB, I will give it a try tomorrow and see if I can find anything that is not right.

shcuck

Well I just want to give you guys an update. Well I fixed the problem. Apperently the short was in the headlight switch. The way I found this out was that I removed the switch to replace it, and when I had it in my hand, it felt very oily and greasy. So at that point I decided to open it, and to my surprise, I found the problem. It had some sort of wax substance that was shorting out all the circuits. I cleaned it very well and reassembled it. It worked like a charm. now I can turn the light on and off as many times as I want with no fuse blowing.

So in conclusion, If you are having problems with your lights, first check the switch, if you have to replace it, it is only $21.00 at Kragen auto parts.