1930 Plymouth 30U Electrical Gremlins

[hursst]

Hello,
  I have a 1930 Plymouth 30U and I'm having problems with the fuse going out all the time now.  I'm out of fuses, so thought I'd ask for some advice.  The car will start and drive just fine, but will have no lights or horn without a fuse.  If I put a fuse in and connect the battery, the fuse will heat up and break in about 8 seconds (30 Amp fuse).  I've had similar problems with the fuse going out in the recent past, both times were when I demonstrated the horn at a car show with the key off.  I would replace the fuse and be fine for a while, now, the fuse won't last at all.

  I assume I have a crossed wire somewhere or a bad ground, but wanted to ask for advice before I start taking the whole electrical system apart past the fuse point.  It's also impossible to test, as I can't get any power to the system without blowing the fuse.  I'm not very skilled with electrical, either.  Any help or advice is greatly appreciated.

[Rusty_OToole]

More likely a wire grounding out intermittently or, a faulty component that grounds out.

 

Here is how to find the problem. Substitute a test light for the fuse. You can make a test light by soldering 2 pieces of wire with alligator clips to a 6V light bulb. Clip the test light in place of the fuse.

 

If the wire is shorting out, the bulb will light up. Now you can go around wiggling wires, tracing where they go, checking your horn and light connections, or whatever your Spidey Sense leads to.

 

When you make the light go on or off you know you are warm.

 

I would be suspicious of where wires go through a hole in the body, or might contact the frame or some metal. If it is the original wiring no doubt the insulation is perished and crumbling.

 

A wiring diagram might help figure things out but really, your wiring is so simple it may not be necessary,

 

You say blowing the horn blows the fuse, so I would have a look at the horn wiring first. Especially the part between the horn relay and horn.

Edited May 24, 2015 by Rusty_OToole (see edit history)

[hursst]

Thanks Rusty.  Just picked up 10 new fuses, but I'll try your test light idea so I can start tracking.  I have a wiring diagram, so that will help, too.

[hursst]

Rusty,

  Thank you for the help. Those were all great tips and I worked off of those tips and some others from another Plymouth forum and ended up finding the problem. It was realy 2 problems. First, I took the horn apart and the solder holding one connection to the horn lead was loose and the other end of the wire that connects to the external connector going to the main wiring harness was very loose as well. I fixed those issues, but still no horn or lights. I took the horn button out, checked all of that and upon re-assembly, I noticed that the horn button shaft had a lot of play in it. I was able to tighten all that up beneath the clum switch, so now the headlight switch isn't sloppy, like it was before. I then traced the wiring past the clum switch and what I beleive is happening is that the horn wiring within the headlight mounting bar was wearing against the horn support bolt that goes through the center of the headlight mounting bar and grounding out on it. I didn't do a full repair yet, but I was able to get the horn and headlights working perfectly now.

This is been an issue for about a year off and on, so nice to have it solved. Thank you again for the assistance!

-Chris