Restoring Ham's '48 Willys: Electrical Problems Solved

Last Friday when I visited the shop, the folks admitted they had an electrical problem that had stumped them.

We had found a miswire on Friday, but even when that was corrected, things looked strange, and no one wants to burn up a new wiring harness. I went in Monday and worked with the guys for a bit. As it turned out, Murphy (of Murphy's Law) had spent some time in the truck. There were two main symptoms; with all switches OFF, there was about a 4 ohm load on the system. Before, during some earlier troubleshooting, the #10 Black/3-white tracer primary power wire got hot - not a good condition.

I was curious as to just how bad a "short" we had on the line, so I connected my 10-Amp meter in series with the primary power line. The load was about an amp - not a dead short - so that particular problem wasn't going to burn anything up - at least not in a hurry. Then - the shop tech noticed that the parking lights were ON, burning brightly, even though the headlight switch was OFF. The dome and cluster lights worked as they should. When the headlight switch was pulled out to the middle position (PARK) the parking lights stayed ON, and with the switch full out, they went OFF, as they should. We rolled under the dash and started tracing wires. Everything checked OK. Hmmm ...

Then the tech noticed that, with the headlight switch OFF, pushed all the way in, the parking lights would blink as the switch knob was wiggled. Someone suggested that the switch that I had overhauled was defective, but I wasn't convinced. I told the tech to take the knob off the switch (setscrew and a threaded shaft). With no knob, the switch and lights worked as they should. My solution, turn the switch OFF (pushed all the way in), then screw the knob on until it just almost touches the panel. That solved the problem. The knob was on the shaft too far and wouldn't let the switch innards go all the way to the OFF position.

So we started hooking wires back to terminals around the ammeter. The tech reported that, when he hooked the two black wires to the + terminal of the ammeter, things sparked and got hot - still. Two # 10 Black/3-white tracers go to the + ternimal of the ammeter. One is the primary power from the starter hot terminal, the other is power to, of all things, the horn. I rolled under the dash again, sorted out black wires and had the tech connect just the hot lead to the meter. No sparks, no heat. But, when I touched the wire to the horn terminal, lots of sparks. Huh ...

It took a minute or two with the meter, but the terminal of the horn that connects to power was shorted to ground. Both horn terminals should have fiber insulating washers under them, one was missing. When folks took the horn apart to clean it, one insulator either got lost, or had disintegrated.

So, we scrambled through the parts drawers, found a washer, put things back together and - SUCCESS. No sparks, nothing gets hot. We checked out several more things (dimmer switch function, high beam indicator) - things like that. It looks like we've found the harness problems we went after.


I've never seen a shorted horn terminal. As we've said in this forum many times; "When you're working on an old Jeep, trust nothing!"

If all goes well, we should have engine start this week...

I'm attaching one photo today. There seem to be a lot of ways to jury rig a throttle return spring to Jeeps, and good pictures of how the spring really should be rigged are scarce. Here's how we rigged our spring. We used the little tab on the linkage - which we suspect is how things were intended - but we couldn't find where the other end went. We made a little bracket an it seems to work OK.