I’ve noticed that my headlight switch becomes extremely hot to the touch when the headlights are on. Not just warm, but so hot that it can possibly cause a burn to the skin.

I’m assuming there is some resistance being built up somewhere in the circuit and escaping as heat, and I was curious where I should check for this issue. I’m very concerned that plastics will melt or a fire may start if I have to leave the headlights on for any extended period of time.

If it matters, the headlight switch works perfectly and the dimmer does too. The switch is not functionally defective, there’s just a ton of heat building up somewhere.

 

There is a big ceramic rheostat that operates the instrument lights that gets hot. What your describing is normal.

 

I would expect the headlight switch to get warm, but not hot, certainly not hot enough to burn.

Check for excessive voltage drop in the headlight circuit. Get a voltmeter, start at the passenger side headlamp. Put the positive probe on the low beam wire (I think it’s light brown or tan) and the negitive probe on the POSITIVE post of the battery. Turn on the headlights. Whatever the reading is on the meter is how much voltage is being lost in the wiring. Hopefully you don’t see more than a couple tenths of a volt. If so, check all the connections for corrosion, scrape all the tarnished terminals until the are shiny, apply a little dielectric grease to keep them clean. Check the dimmer switch, drivers headlight, etc

You can systematically eliminate connectors by moving the positive probe back towards the headlight switch. By starting with the passenger headlight, that’s as far from the headlight switch as possible. Next, check the drivers headlight, then the wire at the dimmer switch, etc.

I wouldn’t let this go. If the headlight switch is hot enough to possibly burn, your going to probably find melted connectors and brittle wiring.

Once the problem is found and repaired it’s pretty easy to put the headlights on relays. That eliminates to long wiring path and takes a big electrical load off the dash harness.

I have seen some pretty nasty electrical harness fires from shoddy electrical work. It’s usually worst on old square body trucks after people put snowplows on them with auxiliary lighting. Their idea of proper electrical wiring is a roll of cheap wire, some butt connectors, and channel lock pliers. Don’t forget some wire nuts!!

read this. http://www.madelectrical.com/electri...adlights.shtml

 

You can do a simple test to determine if the ceramic rheostat is causing the heat.

Turn the rheostat past the detent so that the dash lights are full on. If this stops the heating, then your rheostat is the problem.

 

Change that switch out if you haven’t already. Mine ignited while I was driving home last night. Lucky the rheostat was the only thing that burned. They are cheap enough and fairly easy to change

 

Yikes, that is scary.

I’m seeing lots of bad reviews for modern production replacements. I think I’ll try cleaning this original one first—I’m certain it’s just resistance built up on the contacts from age/corrosion.

 

Sure enough, my switch has heavy heat damage/signs of arcing on the rheostat. It was a matter of time before it was gonna burn up.

I bought an aftermarket unit on Amazon for around $17. Comparing to the original Delco Remy switch, I found it to be of good quality and identical in size.

I had the old one out and the new one in and working in about 10 minutes. Super easy job with no removal of dash parts necessary. One big electrical connector plugs in, making installation very simple. Very satisfied.

 

Make sure the whole headlight circuit grounds are good. You could have the same problem again.
We forget these cars are 40-50-60+ years old. Some of the grounds were shot when the car was 10 years old.

 

Good point. I’ll keep an eye on the heat level but it’s good for the time being.