Headlight switch fire?
Thread Starter
Intermediate
Joined: Jun 2007
Posts: 40
Likes: 1
From: Austin TX
Headlight switch fire?
I just finished a frame off resto of a '72.
My headlight switch got so hot (when I left the parking lights on for about 10 minutes) that it caught my dash on fire. I had just finished the restoration and had no problems while driving with the headlights on for 30 minutes. BUT.... when leaving the parking lights on, the light switch got so hot it actually caught the dash pad on fire! It looks like it was a replacement switch (not original).
Has anyone heard of this happening before? I have aftermarket gauges, and the dimmer on the light switch did not work properly... i.e. my guage lights were on but did not dim.
thanks,
Mark
My headlight switch got so hot (when I left the parking lights on for about 10 minutes) that it caught my dash on fire. I had just finished the restoration and had no problems while driving with the headlights on for 30 minutes. BUT.... when leaving the parking lights on, the light switch got so hot it actually caught the dash pad on fire! It looks like it was a replacement switch (not original).
Has anyone heard of this happening before? I have aftermarket gauges, and the dimmer on the light switch did not work properly... i.e. my guage lights were on but did not dim.
thanks,
Mark
Terrorizing Orange Cones
Joined: Oct 2007
Posts: 2,572
Likes: 17
From: Northern CO
Wow. You didn't mention losing anything more serious than the switch and dashpad; hope you and the car are ok.
Was the HL switch already in the car when you bought it or part of the resto? If it did not dim correctly, the reostat portion was inop but question is why? I wouldn't suspect the aftermarket gauges if they are quality units like Autometer or what used to be Sun, as long as they are wired per spec.
Was the behind-dash harness modified? I'd be suspicious of hot leads or grounds mis-wired but don't know how much overall damage you sustained.
Any pics you can post? Need a little more info.
Was the HL switch already in the car when you bought it or part of the resto? If it did not dim correctly, the reostat portion was inop but question is why? I wouldn't suspect the aftermarket gauges if they are quality units like Autometer or what used to be Sun, as long as they are wired per spec.
Was the behind-dash harness modified? I'd be suspicious of hot leads or grounds mis-wired but don't know how much overall damage you sustained.
Any pics you can post? Need a little more info.
Thread Starter
Intermediate
Joined: Jun 2007
Posts: 40
Likes: 1
From: Austin TX
got the fire out fast... It was in my trailor loading it at night!
The switch was in the car when I got it, but doesn't look original - looks too new and nice, and has a white sticker on the side with a part number? The sticker is not yellow and faded. The gauges were Autometer... they lit up properly, but did not respond at all to the dimmer/reostat on the switch - just always on when the light switch was on. The dash harness was modified to connect to my autometer gauges, and several wires were cut and taped because not used.
The cause is clearly visible as the switch is melted, blackened, etc. Send your email so I can post pics.
The switch was in the car when I got it, but doesn't look original - looks too new and nice, and has a white sticker on the side with a part number? The sticker is not yellow and faded. The gauges were Autometer... they lit up properly, but did not respond at all to the dimmer/reostat on the switch - just always on when the light switch was on. The dash harness was modified to connect to my autometer gauges, and several wires were cut and taped because not used.
The cause is clearly visible as the switch is melted, blackened, etc. Send your email so I can post pics.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Terminals 3 and 5 can get really hot if they don't make good contact. I solder 3 and 5 on a new switch before I install them because they are just pushed through a piece of copper and that copper carry's a big load. You can see in this pic where I soldered them.
Thread Starter
Intermediate
Joined: Jun 2007
Posts: 40
Likes: 1
From: Austin TX
Thanks..... I have my newly ordered switch in my hands and understand what you are talking about. That's exactly where my old switch looked like it failed.
My new switch does not have a "terminal 7" as yours does.... I don't have my old switch to compare it to. I wonder why?
My new switch does not have a "terminal 7" as yours does.... I don't have my old switch to compare it to. I wonder why?
Safety Car
Joined: Oct 2007
Posts: 3,729
Likes: 267
From: Austin Texas
Corvette of the Year Winner 2017
2016 C3 of Year Finalist
DO NOT leave the dash lights dimmed, that generates alot the heat from the Dimmer.
Leave them on full Brightness, Not dimmed, poor design. 69VETT
Leave them on full Brightness, Not dimmed, poor design. 69VETT
Race Director
Joined: Apr 2000
Posts: 17,676
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Don't know why it happened but I had smoke coming out from under my dash when I first bought mine when I was driving around with just the parking lights on and no headlights. I never did figure out why it happened I never drive with just the parking lights on after that 
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Thanks..... I have my newly ordered switch in my hands and understand what you are talking about. That's exactly where my old switch looked like it failed.
My new switch does not have a "terminal 7" as yours does.... I don't have my old switch to compare it to. I wonder why?
My new switch does not have a "terminal 7" as yours does.... I don't have my old switch to compare it to. I wonder why?
You mentioned your instrument lights were on bright all the time, was your green wire (instrument light wire) on terminal #3 (its normally on #2)? Terminal #3 would bypass the rheostat.
edit- terminal #3 is also not used or blank in the connector
Last edited by ...Roger...; Oct 2, 2009 at 06:17 PM.
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Pro
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My (original I think) switch gets hot when driving with the headlights on.
Dimmer worked kind of on and of but lights always stayed very dim.
Had an alternator failure on the highway last saturday and just limped into a Rick Johnson(?) 5 min before closing.
Dimmer works fine with the new alternator (head scratching?)
Need to check if the switch still gets hot.
Dimmer worked kind of on and of but lights always stayed very dim.
Had an alternator failure on the highway last saturday and just limped into a Rick Johnson(?) 5 min before closing.
Dimmer works fine with the new alternator (head scratching?)
Need to check if the switch still gets hot.
Race Director
Joined: Feb 1999
Posts: 19,659
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From: Lenoir City Tennessee
Ci 6, 8 & 10 Veteran
St. Jude Donor '05-'06-'07-'08-'09-'10-'11-'12-'13-'14-'15
The same thing had happened to my car in a past life. When I bought my car this was one of the things I found when I got to looking at the car. I started seeing the white powder on the inside of the speedo and tach. When I took the dash apart I found where the switch had been on fire and the dash pad had been burnt also. The powder from the fire extinguisher was all over. The wiring had been repaired by bubba using lamp cord. I never used the lights after finding that. I have since restored the dash harness and light switch. I try to get the car home before dark just to avoid using the lights if possible. Crazy isn't it. There is a fix out there that some have used that takes the load of the lights away from the switch. That is by having the switch turn on relays that power the light.
Race Director
Joined: May 2006
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From: Dayton, Ohio
The headlight switch has 2 power sources. If the overheating is due to the headlights the relay fix will take of that but if the overheating is from the rheostat for the instrument lights it won't.
Thread Starter
Intermediate
Joined: Jun 2007
Posts: 40
Likes: 1
From: Austin TX
Wow... interesting to see others experiencing the same (or similar) problems. My headlights did NOT cause a problem as far as I could see. It only caught on fire when JUST the parking lights were on for several minutes. I can't remember where my dimmer was set (high or low) as my instrument lights on my aftermarket autometer gauges were always on "normal" brightness no matter how the dimmer was turned.
I'm going to solder the 2 connections as was mentioned by "Roger" above, and keep my dimmer set to high. I wonder if I should also wrap the switch in foil or some sort of heat blanket before installing.
Thanks for all the help and input... very informative.
Mark
I'm going to solder the 2 connections as was mentioned by "Roger" above, and keep my dimmer set to high. I wonder if I should also wrap the switch in foil or some sort of heat blanket before installing.
Thanks for all the help and input... very informative.
Mark
Le Mans Master
Joined: Jul 2006
Posts: 8,117
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From: charlotte north carolina
check for shorts in the dash light circuit. put an ohm meter on the lead that feeds the dash lights. someone may have pinched a wire or even grounded a power wire by mistake.
Thread Starter
Intermediate
Joined: Jun 2007
Posts: 40
Likes: 1
From: Austin TX
OK.... figured it out... sort of. My old switch (that started fire) would not dim the gauge lights when you turned the switch. The gauge lights would always burn bright no matter how the dimmer switch was turned. The new switch's dimmer works perfectly with my gauge lights. So, for some reason, the old switch was defective from the start. Weird... and thanks for all the help guys.
Race Director
Joined: Apr 2000
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
I still wouldn't dim the lights even with a new switch if it is the original design. It just heats up and over the years stops working or catches on fire 
Race Director
Joined: May 2006
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From: Dayton, Ohio
Drifting
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From: Somers CT
Race Director
Joined: Apr 2000
Posts: 17,676
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
I am telling you it scared the crap out me, before I had a fire extinguisher to see smoke coming out from under the dash area
Racer
Joined: Nov 2000
Posts: 290
Likes: 0
From: Omaha, NE
Back in 2001 I discovered my switch shaft was pretty hot so posted this same question here. I got this response from Tom Parkinson:
I owned my 79 from 79 to 84 and I think the hot shaft on the light
switch was "normal". Serial number 45802. Went back to check old
records since my recall is sometimes faulty!!
Picked the car up on Aug 13 that year . First service was on Sept 5.
Work order item says " Check H/lamp switch Rod - Gets very hot with
H/lamps on".
There is no record of any switch replacement (and I don't recall that
being done) so they probably told me it was "normal".
So the short version is that my brand new 79 had the problem, I
drove it for 5 years and never had a reason not to believe it was "normal".
I replaced it with improved results but the shaft will still get just barely warm with the instrument lights all the way up. Go figure.
I owned my 79 from 79 to 84 and I think the hot shaft on the light
switch was "normal". Serial number 45802. Went back to check old
records since my recall is sometimes faulty!!
Picked the car up on Aug 13 that year . First service was on Sept 5.
Work order item says " Check H/lamp switch Rod - Gets very hot with
H/lamps on".
There is no record of any switch replacement (and I don't recall that
being done) so they probably told me it was "normal".
So the short version is that my brand new 79 had the problem, I
drove it for 5 years and never had a reason not to believe it was "normal".
I replaced it with improved results but the shaft will still get just barely warm with the instrument lights all the way up. Go figure.