The 15 amp fuse for the interior lights (dome, under dash) blows as soon as I touch a new fuse to the prongs. Why would there be so much current? How do I find the problem?
Also my taillights do not work. There is no voltage to them at all when I turn on the head lights. But my brake lights and turn signals work fine and I do have the dual light bulb. So I am think the taillights and interior lights may be on the same fuse.
Ryan, Somewhere that circuit is making direct contact with ground. Look at the wiring diagram to determine everything that is connected to that circuit and start looking for a wire crushed against something, a loose wire that is touching something, a bad a broken or loose socket, something metal that has lodged across terminals, etc.
Yeah, it is defiantly a direct short. Conduct an overall visual inspection of the wiring circuit affected as Jim recommended. If you can’t find it that way, then go over the schematic and check for continuity between circuits that are un-grounded circuits and ground. If you find one that has continuity to ground then you have found your problem. This is going to take some time and patience to find so just stay at it.
Thanks guys. It worked when I first re-wired the car. Then all of a sudden it woudn't hold the fuse. So you must be correct in that there is an exposed wire in contact with ground. That make sense. The car is off to have the top installed so I won't be able to look at though.
If you don't have one already go out and buy a multimeter. You can get one for 20 bucks at radio shack. It will have a switch where you can measure resistance. Take the fuse out and hook one lead to the side of the fuse that goes to the car wiring and the other on the chassis. It will probably read 0 (ohms) because there is a short.
Now take out all of the bulbs and whatever is fed from that fuse. If it still reads 0 (full needle deflection) then there still is a short. Inspect the wires you can see if bare metal wire is touching the chassis.
If a wire goes behind a firewall or somewhere you cannot see then isolate that branch by cutting the wire. You will see when you find the branch that is shorting when the needle does not show 0 (full deflection). Note that a bulb/motor/coil can show very little resistance and you will have to look carefully to see the difference between a short and a bulb on the multimeter.
Thats a good point chasen. Dont use the dummy alarm function if your meter has one. This is a alarm that will sound when the meter "see's" a certain amount of resistance. This resistance can be very little and register as a continuous circuit even when its not. You want to looks and see how many ohm's there are on the circuit.
Quick check: Check the bulb and socket in the glovebox. It is on that fuse in the '68 and it is a crummy design. I've had that short out when the bulb was out. That wire and terminal pops out and hits the dash framework.
just if you don't know. You can splice the wire back again by pulling some crimptubing over the wire, then soldering it, pulling the tubing over the solder joint and then shrink the tubing with heat. It makes a great a durable spice.
you can buy the crimp or shrink tubing at radio shack. It comes in different diameters. It shrinks to about half diameter. Any heat will work - even a match held an inch away.
I was able to find the short and it was something very stupid. One of the under dash light sockets was cracked so I purchased one from Murray’s Auto. The original had a plastic housing and the new one had a metal housing. I didn't think it would matter because you couldn't see it anyway. I then went back and replaced the metal one with a plastic one and I now know that it was plastic for a reason! No short with the plastic housing. Lesson learned.
Now I have a similar fuse problem with my tail lights that I have yet to diagnose.
