Headlight Switches

[Dan D.]

Re: Headlight Switches

Paul, that is quite a saga. Not good. If you still have any of these switches, I would love to evaluate it (them) for you. Other than the dash light short, I believe all your problems are with the circuit breaker(s), and these I can usually fix. I am trying to determine if these switches are manufactured by the same company. Our suppliers will not tell me where they are made, other than off shore, but the quantity is just not there for multiple sources to tool up. If the switches look identical, that adds credence to the one supplier theory. I just need a larger sample size.

-Dan-

[Paul Y.]

Re: Headlight Switches

Dan, I was able to return the switches for the 63 but I still have the one for the 66 El Camino installed. I would be happy to send you that one when I finally get around to changing it out beings that it is way too long for the vendor to accept it as a defective return. When I psych myself up enough to get to it I will let you know. I'm doing a front clip on my 63 right now which is consuming lots of time and effort but I will get to the El Camino eventually. Paul

[Dan D.]

Re: Headlight Switches

Okay, thanks Paul.

-Dan-

[William F.]

Re: Headlight Switches

Wanted to say that so far, no problems with the Lectric Limited headlight switch that I installed last week in my '62 . (The blown fuse was an unrelated problem, I assume, since no problems after this was taken care of.)
Dan, How are your tests of various headlight switches coming?

[Dan D.]

Re: Headlight Switches

Well, they were coming good until I blew up my power supply yesterday. I bought a new one on E-Bay but won't have it until Wednesday or Thursday. Did not have a good day yesterday. Problem developed with my test fixture too, but I have that all fixed now. Not so the power supply.

-Dan-

[Richard M.]

Re: Headlight Switches

Well, they were coming good until I blew up my power supply yesterday. I bought a new one on E-Bay but won't have it until Wednesday or Thursday. Did not have a good day yesterday. Problem developed with my test fixture too, but I have that all fixed now. Not so the power supply.

-Dan-

Dan, That stinks, just when things are going good, kaboom! Sorry to hear that.

Reminds me of when I was troubleshooting that TI stuff a while ago when my oscilloscope fried up it's transformer.

Rich

[Dan D.]

Re: Headlight Switches

Yea, Rich. It definitely has a bad smell to it. But I just got a confirmation e-mail that my new one has shipped. That should get me going again.

This is a small, cheap 30 amp switching regulator supply and I am running it hard - 25 and 30 amps for extended periods of time. I fried the in-rush current limiter - nothing left to it other than ashes. I should be able to fix it, but I have to determine what the specs are. Should be around 4 amps - 110 volts.

I remember your o-scope failure. But you made out great on that one!

-Dan-

[Richard M.]

Re: Headlight Switches

Yea, Rich. It definitely has a bad smell to it. But I just got a confirmation e-mail that my new one has shipped. That should get me going again.

This is a small, cheap 30 amp switching regulator supply and I am running it hard - 25 and 30 amps for extended periods of time. I fried the in-rush current limiter - nothing left to it other than ashes. I should be able to fix it, but I have to determine what the specs are. Should be around 4 amps - 110 volts.

I remember your o-scope failure. But you made out great on that one!

-Dan-

Nice.

Yes that new storage scope was a awesome donation from a fellow member from Vermont.

Rich

[Thomas H.]

Re: Headlight Switches

I fried the in-rush current limiter - nothing left to it other than ashes.
-Dan-

Keep in mind that those headlamps with a cold filament have a pretty high inrush current - maybe on the order of 100 amps or so. The car battery can easily supply that kind of current, but bench type power supplies struggle. You could put a low ohm resistor inline, put a scope (since the subject of Oscilloscopes has crept into the thread....) across it and capture the inrush (using a battery as your power source).

I did some testing several years ago on a 28Vdc landing light used on a Piper aircraft. Operating current was in the order of about 12 amps but the inrush when the lamp was cold was over 200 amps! We also lost a power supply after many power cycles. Ended up using a battery bank (almost infinite current avail) and captured the inrush. Became quickly evident why the power supply was toasted (It was my favorite supply too!).

Keep up the good work!

Tom

[Dan D.]

Re: Headlight Switches

Thanks for that info Tom. I did not think the in-rush current in headlights was that high, but I do believe it. The cold resistance must be very low.

As far as the breaker in the headlight switch, they are thermal so they are able to handle it. That is probably why taillights and such are fused (1958 and up), while the headlights remained thermal breaker.

My testing is being done using a resistor load bank, so in-rush should not exceed the 25 or so amps I am pulling. However, I have been thinking about the fried surge protector, and I think I have figured out why it fried. The supply I am using is a low cost supply designed for use with LED banks, which are steady state current with no in-rush. You could say that my testing is steady state too, except when the breaker opens. If you 'tease' the breaker with slight overloads, which is what I am doing, the breaker just barely opens and then pulses on and off quite rapidly. In fact it arcs. So the supply goes from no current to full current and then back again several times. The in-rush protector has to follow this and most likely cannot hold up to this routine. I am going to try putting a large capacitor on the 12V and see if that helps. I also plan on trying to measure the in-rush using a low value resistor in series with the protector, like you have done, and measure the voltage drop across it on my scope. The protector is on the neutral side of the line, so I should be able to do this without having to 'float' the scope ground. The protector is apparently doing its job of protecting the MOSFETS, as they are still alive. What I would really like is a lab type power supply, but based on what you have seen, a car battery would be a better choice.

-Dan-

[Richard M.]

Re: Headlight Switches

Dan,

A new thought regarding the HL switch when installed in the car. We talked about corrosion in the harnesses, etc as a factor in overall load effects. Here is another part of the circuit that could affect load current. The Dimmer switch. You may want to include a Dimmer in future tests as it has a small resistance. My tests of my '59 were through a original switch(NOT the one below), but I never tested it's resistance. A good test would measure resistance of a complete circuit in a car from HL switch harnes right out to the headlamp harness terminals.

This original Dimmer was used to test the electrical system while waiting for a replacement. High beams were intermittent. The following sequence shows the variation in resistance readings and a dissasembly of the switch. Obviously, it's exterior installation at the face of the firewall in the C1 cars makes it more susceptible to corrosion.

Rich

[Dan D.]

Re: Headlight Switches

Interesting find Rich. Were you able to re-stake and use that switch? I always wondered what was inside those switches.

Everything from the battery feed to the headlight switch and then to the bulb is suspect. You can expect corrosion at every termination. But some small resistance, with its series R, will just limit the in-rush current, and that should be good, although they wont be as bright as they should be.

Tom Heys posted an in-rush current scenario which I did not think about and is very interesting. I am going to measure the in-rush on my 57 as soon as I get back in business here. I hate to dump work on you Rich, but if I send you a low value resistor, could you sometime measure the in-rush on your 59? With your digital scope, you could capture some plots of it. That would be very interesting to know as the 4 light Halogens should represent the worst case scenario. No hurry on this.

Just in passing, I would not recommend using a relay to circumenvent a bad headlight breaker. You would definitely want to fuse it if you do, but I believe the in-rush will slowly degrade a fuse to the point that it will blow. That happened to me several years ago with an old Japanese truck that used fuses instead of a thermal breaker. Switched on the brights and everything went out. Scary thought. A slow-blow fuse might be okay, but the best thing to do is find a good headlight switch. From what I am learning, I believe GM put a lot of thought into this design, and they did it just right. They could not have done it any better, given the technology at that time. I would love to know how new cars do it.

I have my new power supply and am currently re-doing my resistor load bank. What I have been using was a first attempt and it needed some upgrading. Finished up my taxes (UGAAAH), and now the wife is making noise about the Easter ***** and the grand kids. I should be back in business by Monday.

-Dan-

[Thomas H.]

Re: Headlight Switches

I have a digital scope and a current probe. I'll do some measurements on my 60 - hopefully next weekend. Need to go get it out of storage.

I was going to get it today, but I spent the whole day installing a back splash in the kitchen. The culmination of a kitchen remodel that has taken me about a month to do. Once I do the grout and paint some trim I'm done and can get back to playing with the cars!

Wife told me a while ago that before I get a bigger garage she gets a new kitchen.................. Check that off the list!

Tom

[Darryl D.]

Re: Headlight Switches

So, the bottom line here seems to be if you have a 56/57 you should look for a junk yard 57 passenger car with an original GM headlight switch and dimmer?

[Richard M.]

Re: Headlight Switches

So, the bottom line here seems to be if you have a 56/57 you should look for a junk yard 57 passenger car with an original GM headlight switch and dimmer?

Darryl, Yes if you need original parts. Chances are those 60 year old parts will need restoring though. Not many will be perfect.

Interesting find Rich. Were you able to re-stake and use that switch? I always wondered what was inside those switches.

Everything from the battery feed to the headlight switch and then to the bulb is suspect. You can expect corrosion at every termination. But some small resistance, with its series R, will just limit the in-rush current, and that should be good, although they wont be as bright as they should be.

Tom Heys posted an in-rush current scenario which I did not think about and is very interesting. I am going to measure the in-rush on my 57 as soon as I get back in business here. I hate to dump work on you Rich, but if I send you a low value resistor, could you sometime measure the in-rush on your 59? With your digital scope, you could capture some plots of it. That would be very interesting to know as the 4 light Halogens should represent the worst case scenario. No hurry on this.

Just in passing, I would not recommend using a relay to circumenvent a bad headlight breaker. You would definitely want to fuse it if you do, but I believe the in-rush will slowly degrade a fuse to the point that it will blow. That happened to me several years ago with an old Japanese truck that used fuses instead of a thermal breaker. Switched on the brights and everything went out. Scary thought. A slow-blow fuse might be okay, but the best thing to do is find a good headlight switch. From what I am learning, I believe GM put a lot of thought into this design, and they did it just right. They could not have done it any better, given the technology at that time. I would love to know how new cars do it.

I have my new power supply and am currently re-doing my resistor load bank. What I have been using was a first attempt and it needed some upgrading. Finished up my taxes (UGAAAH), and now the wife is making noise about the Easter ***** and the grand kids. I should be back in business by Monday.

-Dan-

Dan, When I get time I can do some more experiments on my '59. Tom may be able to also. I have plenty of electronic components here so don't bother sending anything, just tell me what the value/wattage values.

I didn't repair that dimmer switch yet but I will and save it for later. I repaired a original dimmer for a '67 not long ago and it worked fine after I repaired it.

Rich