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Author Topic: '66 Cadillac headlight switch  (Read 4077 times)

'66 Cadillac headlight switch
« on: August 20, 2014, 11:03:57 PM »
I have a problem with the headlight switch in my ’66 Eldorado. The car has both Guide-Matic and Sentinel. I don’t want to force it, but the pull switch appears to have only one position. I believe it should have a detent for the fog/ turn signal first, then extend fully for the headlights. The headlights and high beams work when I pull the switch out as far as it goes. In this position all the dash lights are dim and the rheostat dimmer  does not work properly. The dash lights only work about the mid rotation point of the rheostat then go out as you continue rotation. Additionally the small lights on top of the fenders that  show blinker light functions work properly with the headlights on or off, but are not lit when the headlights are on and the blinkers are not in use.

Am I correct that the headlight switch is universal for ’66 and that the Guide-Matic and Sentinel capability are separate add on parts that plug into the switch?

Is the switch grounded through its mounting to the dash or is there a separate ground wire?.....When I installed the cluster I didn’t have any leftover wires or plug pins.

Thanks,

Ralph
1966 Fleetwood Brougham-with a new caretaker http://bit.ly/1GCn8I4
1966 Eldorado-with a new caretaker  http://bit.ly/1OrxLoY
2018 GMC Yukon

Offline Eldo66

  • Posts: 83
  • Name: P Nesbitt
Re: '66 Cadillac headlight switch
« Reply #1 on: August 20, 2014, 11:53:03 PM »
Ralph,

My headlight switch was original and shorted out 6 months after I bought the car - melted the attached wiring connector and was a serious fire hazard.  I recommend against driving your car (esp. at night) until you replace it.  Also, since a heavy gauge wire feeds battery power to the switch even when parked, keep your battery disconnected too. 

The switch is a standard one used on many GM models.  I found a non OEM replacement at my local auto parts store for $15.  Turns out GM used similar switches on GMC trucks until the late 80s that matched the original 1966 GM part number.  It has worked fine for 2 years.  I will try to find the current part number and post it.  Will eventually replace it with a restored original.  The dimmer and sentinel controls attach around the shaft of the standard switch. 

I can't remember how the switch is grounded. 

Regards, P. Nesbitt
1966 Eldorado - Flamenco Red with bucket seats

Offline Commodore

  • Posts: 47
  • Name: Steve Marshall
Re: '66 Cadillac headlight switch
« Reply #2 on: August 21, 2014, 12:47:26 AM »
The non OEM replacement is a Standard Motor Product DS155, an ACDELCO D6251D or an Airtex/Wells 1S1367. See photos.




Offline Philippe M. Ruel

  • Posts: 586
Re: '66 Cadillac headlight switch
« Reply #3 on: August 21, 2014, 02:12:25 AM »
Headlight switch failure is common after bearing such high current for 50 years.

Many people suggest feeding headlights through relays, the way it's been on most cars for 20-30 years. Relays dramatically decrease current through the switch, increasing its life expectancy. They decrease authenticity, too, but may be installed in a 100% reversible way by using proper connectors.

I installed a pair of relays (one for high beam, one for low beam) on my 1966 F*rd a few years ago, after the second non-OEM Chinese switch burnt. I plan to do the same on my Caddy, to make her original switch last as long as possible - it only took some time locating the necessary 6V gear.
1952 60 Special in France.

Offline cadillactim

  • Cadillac Tim
  • Posts: 799
Re: '66 Cadillac headlight switch
« Reply #4 on: August 21, 2014, 09:11:24 AM »
Ralph

The switch is grounded through the mount point, no extra grounds. The signal indicators on the fenders only work when the signal is on, they do not turn on any other time.

The guidematic and sentinel rheostats are separate from the switch, though they mount in front of the switch.

Your switch should have two detents, the first for the park lamps, the second for headlights. When you rotate the knob from one extreme to the other the dash lights should gradually go from bright to off.  The coil on these get corrosion build up and don't work very well over time.  Sounds like you need a new switch.

Tim
Tim Groves

Offline 76eldo

  • Posts: 6651
  • CLC Number: 22443
  • Name: Brian Rachlin
Re: '66 Cadillac headlight switch
« Reply #5 on: August 21, 2014, 09:47:27 AM »
I was reading this thread just to get some info as I have also had problems with headlight switches over the years.
The info and quick responses are impressive guys. I think this must be one of the best sources of Cadillac info available anywhere.

Brian
Brian Rachlin
Huntingdon Valley, Pa
CLC # 22443
I prefer email's not PM's rachlin@comcast.net

1960 62 Series Conv with Factory Tri Power
1970 DeVille Conv
1970 Eldo
1970 Caribu (?) "The Cadmino"
1973 Eldorado Conv Pace Car
1976 Eldorado Conv
1980 Eldorado H & E Conv
1993 Allante with Hardtop (X2)
2008 DTS
2012 CTS Coupe
2017 XT
1956 Thunderbird
1966 Olds Toronado

Re: '66 Cadillac headlight switch
« Reply #6 on: August 21, 2014, 01:24:12 PM »
Guys,

Thanks for the suggestions and help. You confirmed my suspicions. I have a new Delco switch on order.

I must second Brian’s comment. The knowledge on this forum is encyclopedic and members are most generous and helpful. I too read many of the technical posts and always learn something new.

Ralph
1966 Fleetwood Brougham-with a new caretaker http://bit.ly/1GCn8I4
1966 Eldorado-with a new caretaker  http://bit.ly/1OrxLoY
2018 GMC Yukon

Offline Julien Abrahams

  • Posts: 473
  • Name: J. Abrahams
Re: '66 Cadillac headlight switch
« Reply #7 on: August 22, 2014, 04:27:07 AM »
I had the exact same problem on my '67 headlight switch: the rheostat would not work properly: dash lights would go from very dim to brighter and brighter, then turn off, and then turn on at the brightest setting ;). Also, when driving one night, the headlights just turned off. A bit scary on a road without any streetlights.
Replaced the switch, and all is well. Its probably the kid in me, put I really like the feature that the dash lights can be dimmed. In my view a bit unnecessary, but so cool :D. But I have that with most features on the car (like the electric antenna, signal seeking radio and the climate control).
1967 Cadillac Sedan De Ville HT
1969 Austin Healey Sprite
1979 Opel Kadett

Offline Glen

  • Posts: 2789
  • CLC Number: 727
  • Name: Glen Houlton
Re: '66 Cadillac headlight switch
« Reply #8 on: August 23, 2014, 02:05:41 AM »
Sometimes you can restore the dash light dimmer by just turning it back and forth.  It cleans off the resistor.  But sometimes the resistor wire burns through.  That happens when the knob stays in one place too long.  It is a good idea to move the knob every once in a while. 
Glen Houlton CLC #727 
CLCMRC benefactor #104

Offline Panoply

  • Posts: 10
  • Name: D gussack
Re: '66 Cadillac headlight switch
« Reply #9 on: July 29, 2016, 09:38:33 PM »
On my '66 the guidematic and sentinel control rings hang loosely and unconnected.
Still, when I turn the headlights on it seems to be on auto since the brights come on and occasionally turn themselves on and off.
How do you turn the brights off and keep them off?
Thanks.

Offline Julien Abrahams

  • Posts: 473
  • Name: J. Abrahams
Re: '66 Cadillac headlight switch
« Reply #10 on: July 30, 2016, 04:09:59 AM »
By using the vfoot switch you cab override the auto dimming feature.
1967 Cadillac Sedan De Ville HT
1969 Austin Healey Sprite
1979 Opel Kadett

 

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