Author Topic: 1956 headlight switch assembly  (Read 433 times)

Offline Rob Leech

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  • Name: Rob Leech
1956 headlight switch assembly
« on: October 08, 2017, 06:54:15 PM »
I had to move my headlight switch out of the way to access my trunk open dash light. I have the dash pad off and after the moon and stars aligned, I finally was able to remove the shaft out of the switch by pressing the button on the back side of the switch. I think the flat side of the bar also had to be in the right position. The problem I'm having now is the shaft won't seat all the way back into the switch, it lacks about 3/4 of an inch. I have a spare switch and the shaft will go back into that one fairly easily. I am bumping into something solid in the switch. I have tried turning it in all directions and tried to tap it in as hard as I dare for fear of breaking it. Any suggestions? I really don't want to take it all the way out, it looks like a major undertaking, Thanks for any suggestions.

Read down a few posts, I fixed it and explained a fairly simple procedure to get the rod back into the switch.
« Last Edit: October 19, 2017, 06:25:44 PM by Rob Leech »
Rob Leech 1956 Eldorado Convertible

Offline J. Gomez

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Re: 1956 headlight switch assembly
« Reply #1 on: October 08, 2017, 07:55:57 PM »
I had to move my headlight switch out of the way to access my trunk open dash light. I have the dash pad off and after the moon and stars aligned, I finally was able to remove the shaft out of the switch by pressing the button on the back side of the switch. I think the flat side of the bar also had to be in the right position. The problem I'm having now is the shaft won't seat all the way back into the switch, it lacks about 3/4 of an inch. I have a spare switch and the shaft will go back into that one fairly easily. I am bumping into something solid in the switch. I have tried turning it in all directions and tried to tap it in as hard as I dare for fear of breaking it. Any suggestions? I really don't want to take it all the way out, it looks like a major undertaking, Thanks for any suggestions.

Rob,

If you can get the shaft all the way even when you push the release bottom under the headlight switch.  :o

The only thing I can think off is the latch inside the headlight switch (the one is pushed by the bottom to release the shaft and the shaft slides inside) may have latched inside or the small spring which pushes back into the lock position is broken which will block the shaft to engage all the way in.

Sometime you can press the bottom and rotate the shaft to get it all the way back, but. ???

If all fails sorry but the alternative is to ... well you already guess it on your last sentence.  :-X

Good luck..!
J. Gomez
CLC #23082

Time is irrelevant when you work on your classic car, eventually you will enjoy it..!

Offline Rob Leech

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Re: 1956 headlight switch assembly
« Reply #2 on: October 08, 2017, 08:06:11 PM »
Thanks J. I have tried it by pushing the button and spinning the shaft. On my spare switch, it will click in without pushing the button. You have to push it to release the shaft for removal. It may be broken. Going to try a while longer before giving up. Thanks for the suggestion. Rob
Rob Leech 1956 Eldorado Convertible

Offline lexi

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Re: 1956 headlight switch assembly
« Reply #3 on: October 09, 2017, 01:11:28 AM »
If you have to disassemble the switch, place it in a ziploc bag to keep the small parts from getting lost. Just in case you had other spare parts lying around, (you did mention a "spare switch'), and you grabbed the wrong one, that could cause a problem. My '56 has fog lights which necessitated GM using a longer shaft. The non-fog light car's headlight rod will not work in the switch equipped with a fog light switching box as it would be too short. Just tossing this idea out, because I sometimes work on my car and bring out spare parts for comparison purposes to assist with the work. You can mix things up. That said, I ran into the same problem as you did and found I had to swap out the rod with a spare one from my parts. Did not study it but seems the slot cut into it just wasn't grabbing the latch plate inside. Clay/Lexi

Offline Rob Leech

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Re: 1956 headlight switch assembly
« Reply #4 on: October 12, 2017, 08:07:10 PM »
Lexi; thanks for the tip about the zip lock bag. The lock collar in the switch had moved and caused a jam. I disassembled the switch.  :(  It exploded in a dozen directions when the top came off. Still lost some parts and had to hunt for an hour to get all the pieces. I had no chance to see how it was assembled before the explosion. I had to study the switch for an hour before I was reasonably sure how it worked. Assembly is not for the faint at heart. It took hours and hours to finally line up everything at the same moment. I felt like I had assembled a ship in bottle. Everything seems to be working, getting 12V everywhere. How do you know if the dash lights are going to get brighter as you turn the knob? I am getting 12V all over the spring and everything connected to the spring, even if you rotate the point around the spring. Seems like the voltage should be changing as you dial around the spring. I cleaned and polished everything before I put it back together. Can you tell me how to check if it's going to work properly when I put the switch back in the car. All this because my trunk open light had lost its ground. A five minute fix. Thanks so much
Rob Leech 1956 Eldorado Convertible

Offline lexi

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Re: 1956 headlight switch assembly
« Reply #5 on: October 15, 2017, 07:30:23 PM »
Yes, the headlight switch will 'explode' with parts flying all over the place when disassembled, so the plastic baggie will contain the parts. I also found myself in the same rebuild situation, twice. Once more than 40 years ago and then again a year or two ago, when I had disassembled another switch, then had to relearn how to reassemble it, all over again. Takes about an hour or so. Like assembling 'a ship in a bottle' as you accurately put it. Wife learned some new cuss words. I wondered how these f&%$&@g things were put together at the factory as so much finesse is required to build them. This dash rheostat system is a weak point in these cars.

Any how, I did have problems with my rheostat (dash light dimming stopped working), and a continuity test showed that my rheostat fine gauge wire was OK, (they are usually toast) but as I recall the contacts were corroded. As I recall they are tough to see, and would be a job to tackle. Again, going from memory from a couple of years ago. Think there are some dissimilar metals there and I recall seeing a badly corroded one. Some guys totally rebuild these using a fine ohm resistance gauge wire (30 if I recall correctly), and half fill the cavity with plaster of Paris as a heat sink as well as a retainer for the replacement wire. I never went that route so I reassembled my unit and soldered a jumper between the grey wire (panel lights) and the green wire (tail lights), of the headlight switching unit, as I recall. That way the dash lights are on full strength when you put your lights on. There is no adjustment to your dash lights intensity when powered this way.

Not sure what the voltage would read across the spring between any 2 given points, (if I understand your question), but I would imagine that it should vary depending on the distance between the 2 points when measured as the coil is supposed to modify the voltage. You did not say if your panel lights work at all or not. If you are getting voltage on the rheostat coil but your panel (dash) lights are not lighting up, I suspect that the terminal at the end of the coil is toast, (as was my case). There are senior members better equipped than I to guide you through the paces of attempting a repair. But sounds like you have to (yes) disassemble the unit again, and carefully check the rheostat and it's terminals, as well as the "slider" that runs along it's surface when you rotate the headlight switch knob, making sure it makes contact. Not an electrical genius by any stretch, but I imagine that by connecting your volt meter to the PL (panel light terminal on the HL switch), with a solid ground, should reveal a fluctuating voltage when the rheostat is engaged (if working properly and with power on in the OEM wiring configuration). Below is the electrical diagram to assist. Perhaps check your connections first and keep your ziplock baggie handy! If you are still stuck, I have another switch here for back up, and could dig it out and take some photos (and perhaps refresh my memory).

Thanks to Jose Gomez for having posted this diagram in relation to an earlier thread.

Clay/Lexi
« Last Edit: October 15, 2017, 11:50:08 PM by lexi »

Offline Glen

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Re: 1956 headlight switch assembly
« Reply #6 on: October 16, 2017, 01:16:34 AM »
How do you know if the dash lights are going to get brighter as you turn the knob? I am getting 12V all over the spring and everything connected to the spring, even if you rotate the point around the spring. Seems like the voltage should be changing as you dial around the spring.

The resistance wire is just that a resistor.  To get a voltage difference there needs to be current flow.  If the lights are not in the circuit then you will get the full 12 volts at all points on the resistor coil (spring).  Use the ohms scale on your meter to check the resistor.         
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Offline lexi

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Re: 1956 headlight switch assembly
« Reply #7 on: October 16, 2017, 09:35:41 AM »
That makes sense now that you mention it!Thanks for clarifying that aspect. Brain not working as well as it used to! Clay/Lexi
« Last Edit: October 16, 2017, 09:44:33 AM by lexi »

Offline Rob Leech

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Re: 1956 headlight switch assembly
« Reply #8 on: October 17, 2017, 08:16:36 AM »
Thanks Lexi and Glen. Not knowing much about resistors, I had no idea to use the Ohm meter. I just assumed the voltage would change as I moved the point across the spring. It's not back in the car, I wanted to test everything before I reinstalled the switch. Will know more and report back in a few days. Thanks again for helping on this topic. Rob

A few days later; tested the ohms and saw the reading change around the spring as I moved the multimeter. The dash lights are excellent and they brighten and dim as they should. Thanks again.
« Last Edit: October 19, 2017, 05:58:54 PM by Rob Leech »
Rob Leech 1956 Eldorado Convertible

Offline Rob Leech

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Re: 1956 headlight switch assembly
« Reply #9 on: October 19, 2017, 06:21:24 PM »
 Learned a lot about the headlight switch from this experience. Here is something you should read before you disassemble the switch. I talked to an old friend who has worked on 50's cars since Moby Dick was a minnow. He had assembled several of these GM and Ford switches and never forgot any of them. The problem with putting the rod back in the switch comes from bumping into the locking collar in the switch (which is something you can't see) and pushing it back to the back of the switch housing before the rod locks into position. From there, it won't lock into place. That is exactly what I did wrong to start with. Later in the 60's, GM started putting a hole in the back of the switch housing so you could easily insert a wire and push the switch back to the front of the housing. If the switch is in the front of the housing and you carefully insert the rod while holding down the release spring on the top of the housing, it falls right into place. I drilled a small hole in the back of the plastic housing and pushed the switch to the forward position before I installed it. The rod locked into place perfectly. You still have to remove the switch from the car to do this, but it is a lot easier fix than taking the switch apart. Also make sure when you remove the rod, you have to pull the rod out to the last position, then depress the release spring. It should come out without any problem. Hope this helps anyone who ever needs to remove their headlight switch for any reason.
« Last Edit: October 19, 2017, 06:47:18 PM by Rob Leech »
Rob Leech 1956 Eldorado Convertible

Offline lexi

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Re: 1956 headlight switch assembly
« Reply #10 on: October 19, 2017, 07:10:41 PM »
Great info. To make sure I got this correct, you push a wire in through the hole you drilled at the far end to push up against the locking collar, (to keep it in place)? Or is it used to go up against the moving contact block (or both)? Clay/Lexi
« Last Edit: October 19, 2017, 07:25:53 PM by lexi »

Online Roger Zimmermann

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Re: 1956 headlight switch assembly
« Reply #11 on: October 20, 2017, 02:08:47 AM »
When I restored my '56 Sedan de Ville in 1982, I had no idea about how to remove it from the car. With the upper dash panel removed, I took the switch apart...without loosing a single piece. Only months later I learned about that knob on he top...
1956 Sedan de Ville (sold)
1956 Eldorado Biarritz
1957 Eldorado Brougham
1972 Coupe de Ville (not yet arrived)
2011 DTS
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Offline lexi

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Re: 1956 headlight switch assembly
« Reply #12 on: October 20, 2017, 09:27:39 AM »
Roger I feel your pain. I was more fortunate as the mechanic I worked for accompanied me to an old school wrecking yard out in the boonies back in the 1970s. There was a Caddy there that I needed parts from. I required a wiring harness to fix my '56 CDV which was my ride at the time. It had went up in flames while driving and I desperately required that wiring to repair the electrical damage which was extensive. Vern showed me how to remove the switch by pushing the magic button. What he didn't tell me was how they fly apart when disassembled. Something I learned sitting at my parents kitchen table a week or two later! Clay/Lexi

Re: 1956 headlight switch assembly
« Reply #13 on: October 20, 2017, 01:02:47 PM »
My fingers are still nimble, but it took me an hour or two to reassemble the headlight switch on a 55 this summer.  Tricky business.  I am guessing that when these were made, they had a jig or fixture that helped hold things together as they put it back together.  I can't imagine that they did it all with their hands like I did on the kitchen table. 
Art Gardner


1955 S60 Fleetwood sedan

Offline Rob Leech

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Re: 1956 headlight switch assembly
« Reply #14 on: October 22, 2017, 06:43:13 PM »
 After you drill a small hole in the back of the switch, just use a stiff wire or coat hanger, anything that will slide the inside of the switch to the forward position. Then the rod will lock into the collar easily.

 The only reason to take this switch apart that I can see is to grease it. The white grease the factory put in dried up in 1963. lol
Rob Leech 1956 Eldorado Convertible

Re: 1956 headlight switch assembly
« Reply #15 on: October 23, 2017, 06:36:27 AM »
The reason for taking these apart is to get at the electrodes that carry the current from the mechanical part of the switch (inside the rectangular box) to the rheostat part of the switch.  The switch has little electrodes that make contact with one another.  These corrode and are the main source of the issues with the rheostat.  If you disassemble the switch, you can knock the corrosion off of these easily.
Art Gardner


1955 S60 Fleetwood sedan