1976 S&S headlights all out!

Tom Hoczyk

Tom Hoczyk

PCS Past President
I haven't driven my '76 S&S this year, but after returning from Cadillac LaSalle last summer in Kansas City, for reasons unknown, the headlights are completely out. I have the wiring diagram, and it shouldn't be too tough to diagnose, but I was wondering if anyone else out there had the same problem and can lead me to a quick diagnoses. They've always worked in the past, and nothing unusual has happened to cause this outage. Thanks! Tom
 
Tom,

Pull back the carpet and look at the high/low beam switch and wires/plug,
Just last week I discovered (on my '76 Superior) that the plug itself was melted and the butt conectors on the wires (the plug had previosly been replaced prior to my ownership) were charred, and just yesterday we discovered that the plug conector just a few inches away from the headlight switch at one point got bypassed with the wires for the headlights because those wires burned and melted that plug!! and the butt conectors for THAT bypass were also charred!! I'm worried there may still be some type of short somewhere!!

NOT a happy discovery!! and even though we have repaired what we saw I will have to keep checking to see if it happens again.

To see the wires from the headlight switch it is easier to remove the panel below the steering column and to the left, I think it was like 8 screws.

not sure if this is helpful in anyway but probably worth taking a look!!

good luck!

Dana.
 
Is it just the headlights or all lights that would go on when you pull the headlight switch? It may be the headlight switch itself, or possibly dimmer switch on the floor. Sounds stupid, but I had the dimmer switch go out and caused the headlights to quit. If you pushed on it they worked but as soon as you let off they went out.
 
if just the headlights the dimer switch or the hot wire going to it is first on the list. a lot of time it's just one side that goes out and a click will get you back home. as it's wired hot when the main switch is pulled out a short will fry anything from there to the main switch. but lack of use leads one to believe moisture has corroded the contacts.
 
My guess would be either fuse, or bad ground in the dImmer switch. Floor mounted dimmer switches are bad about getting moisture in them creating corrotion, causing a bad ground,and there for will cause the headlights not to work.

Josh
 
Dana Bennett said:
Tom,

Pull back the carpet and look at the high/low beam switch and wires/plug,
Just last week I discovered (on my '76 Superior) that the plug itself was melted and the butt conectors on the wires (the plug had previosly been replaced prior to my ownership) were charred, and just yesterday we discovered that the plug conector just a few inches away from the headlight switch at one point got bypassed with the wires for the headlights because those wires burned and melted that plug!! and the butt conectors for THAT bypass were also charred!! I'm worried there may still be some type of short somewhere!!

NOT a happy discovery!! and even though we have repaired what we saw I will have to keep checking to see if it happens again.

To see the wires from the headlight switch it is easier to remove the panel below the steering column and to the left, I think it was like 8 screws.

not sure if this is helpful in anyway but probably worth taking a look!!

good luck!

Dana.
Click to expand...

The dimmer switch wires are subject to melt down as a result of high resistance in the circuit. When you have a poor contact in the headlamp dimming switch, it will almost alway result in a burned wire condition.
 
Tom, I had a similar issue with one of my Lincolns. I realize your car is a Cadillac, so maybe my story will be pointless, but maybe it will help too.

On my 1979 Town Coupe-based flower car, the headlights would come on, but then go out after X number of moments, and come back on again after another X number of moments. This cycle kept repeating itself, but the other lights remained lit the whole time. I asked some people knowledgeable about Lincolns about this, and they said that a not common, but not unheard of either, issue with the Lincoln headlight switches of the era, is that the internal circuit breaker inside the switch just plain gets weaker over time, due to dirt, corrosion, and age, and when it does, it will trip fairly easily. They said that one can either replace the switch, or disassemble the switch and clean it up.

What I did instead, is I installed a relay with its own fuse to power the headlights, rather than have the headlight current flow through the switch itself. Now when I pull on my headlight switch, it trips the relay to power the lights. While I was at it, I also decided to power my high beams through a relay as well.

This has proven to be a solution for me thus far.
 
I agree with Paul's diagnosis. FWIW:

GM headlamp switches NORMALLY didn't fail that often in "normal" use. Note the emphasis on normal. One problem "back in the day" in the late 60's to early 70's was when the high beams (round 4001's) were replaced with Aircraft Landing Lights. A flat lens 13V headlamp extremely directional with an approximate output of 100,000 candlepower. At least in southeast Michigan some police departments ran them on their cars.

They were fine when you ran a 12V power source directly to them, either using a relay or a toggle switch to activate them. When you wired them directly in to the car, they would overload the headlamp switches internal breaker. Enough trip times would weaken the breaker.

The only other normal failure would be failure of the rheostat for the dash cluster. Either poor or no contact due to corrosion and arcing.

Floor dimmers are subject to water,dirt and just plain abuse, the best starting point. Made one or two jumpers for temporary use until a switch could be acquired over the years.
 
My experience, I have had several 70's caddy hearses, when they sit along time for what ever reason this happens, pull headlights on and only get parking lights or nothing. I have found that pulling and pushing the knob in and out about a hundred times will sometimes fix it but may as well replace headlight switch. As someone else mentioned sometimes it can be the dimmer switch and that is true too. Usually one or the other.
 
Thanks, all, for taking the time to write and help. Truth is, I've been so busy getting the '60 Eureka ready for Hudson, and later will be getting the '39 Eureka ready for Cadillac / LaSalle in Columbus, that I haven't touched the '76. But I printed out all the replies, and thank you for them. Later in the summer I should be able to spend some time with the '76. I'll definitely post and let everyone know the results. Tom
 
Hello Tom. Did you figure out what your headlight issue was? I seem to be dealing with the same thing now myself.
 
No high or low beams, means that the dimmer switch has gone bad, and / or the wires to the headlamp dimmer switch have burned away the insulation, and this has resulted in a broke wire, or a fire! If the taillights and parking lights illuminate, but not the headlamps, then it is the dimmer switch circuit. If the parking and taillights don't work, then it most likely is the headlamp switch. If the car has either a Guidematic or Twilight feature, then it can be other problems associated with those two features.
 
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