It's Lights Out for my 1950 Land Cruiser.

[TWChamp]

Yesterday early morning is was still dark, so I had my headlights on to drive to the swap meet and car show at the Minnesota State Fairgrounds. When I went to leave the first red light, I pushed the clutch in to shift to first, and my lights went out, the ammeter pegged full discharge, and I could smell a wire getting hot. I immediately pushed the light switch to parking lights, then drove a mile down the road and pulled into a church parking lot. Everything under the hood looked fine, then it dawned on me that my foot likely touched the dimmer switch when I pushed the clutch pedal down, so I pushed the switch to high beams, and everything was fine. I'm sure the dimmer switch took a dump, so I already ordered a new one.

At the swap meet I saw at least 4 dimmer switches, but they all had spade terminals, and Studebaker used screws back then.

[StudeRich]

With a direct short like that causing a full discharge, I would certainly carefully check all of the runs of wire from the Headlight Switch to the Dimmer switch.

I am glad you made it Ok, without a Car fire.

[TWChamp]

Yes, this also explains the occasional ammeter needle showing a high draw when I first turn on the lights a few weeks ago and other times this summer. The needle would show 10 amps discharge, and hang there for several seconds, then come back to plus a couple amps. It did this about half the time I first turned the lights on this summer. It had me puzzled, as I had installed an NOS voltage regulator just after doing the brake job.

[TWChamp]

I haven't crawled under the car yet to see how involved the switch removal is, and was surprised to find no mention at all about the dimmer switch in my 1950 Shop Manual.

My 1952 Motor's Shop Rate Manual says R&R is only .4 hours, so there should be no surprises in the job.

[unclemiltie]

You have to remove the shield to get to the wires. The bolts can sometimes be hard to remove. Otherwise simple job

[jclary]

Few things terrify me more than the possibility of a car fire...especially if I'm in the car! Given how rapid a direct short can heat up and ignite things like plastic insulation, paint, undercoating, upholstery, oil, and gasoline...a vehicle can become fully involved in seconds. Years ago, I was proudly showing my newly purchased GT Hawk to my brother-in-law when at a stop sign, suddenly smoke came boiling from under the dash! I rolled the car into someone's yard and bailed out! My brother in law was more puzzled at my reaction than concerned about the smoke, although he was coughing and choking from the smoke.

I refused to move the car until I traced the offending circuit. Apparently, the previous owner had jury-rigged some wiring with no fuse for the circuit. My guess was that the original wire had been blowing a fuse and instead of finding the short, a piece of wire was patched in with no fuse protection. To make things worse, the patch wire was too small. It lit up like a stove element! I don't recall exactly what circuit (radio?) but I do recall that the heat was so intense that it burned the wire insulation to a crisp!


Fortunately for me, I was only about a quarter mile from home, so I disconnected the wire, drove back home, and didn't drive the car again until I had completely inspected the wiring and corrected any of several questionable patches.

If you have a headlight wire shorting somewhere, it is important to get to it and correct it soon. Especially if your car has an oily underside (like most of mine) and there is much of the tar-like undercoating in the vicinity. A good reason to have and keep a fire extinguisher in your vehicle and easy to get to. Let us know what you find. It could be helpful to all of us in maintaining the safety of our cars.

[TWChamp]

In the early 80's I taught auto mechanics at the Vo Tech for one year. Another auto teacher told his students that if you want to find a short, you replace the blown fuse with a solid wire, then replace all the wires that burn. What a crazy thing to tell the students to do.

I told them it's safe and easy to locate a short. You connect a 2 prong flasher and 1 ohm resistor or light bulb in series, then clip it to the fuse terminals. The short will make the flasher click on and off, and the bulb will take the load to keep the wire from overheating. You then hold an inductive ammeter or even a plain compass next to the shorted wire or harness. The meter or compass needle will deflect with the current draw. When you move past the short, the needle will no longer deflect because there is no current flowing past the short. I thought this up back in the early 70's, and have only used it a couple times to locate shorts, but it works well.

[TWChamp]

I may have jumped the gun for blaming the dimmer switch. Today I sprayed Gibbs on the fasteners, then removed the splash shield and the 3 wires from the dimmer switch. I pulled on the headlight switch, then touched the power wire to the high beam, and it worked fine. I then touched the power wire to the low beam, and it acted like a short with a heavy draw, but after touching it a few times everything was working correctly again. I screwed the wires onto the switch and replaced the splash shield, and now everything is working fine. I'm going to have to do more checking and follow all the wires to make sure none are shorted to ground. When everything is working correctly, then it's harder to find what caused the problem.