GM style headlight switch blues
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Laughing Gas
Joined: Sep 2013
Posts: 1,203
Likes: 146
From: Goulburn, NSW
GM style headlight switch blues
Hi Guys.
I'm nearly finished wiring up the '54 with my Rebel wire kit, and I bought a mid fifty dome light wiring kit to add a dome light to the setup.
I bought a GM style headlight switch to make wiring up a tad easier. All works fine except when I try to dome light.
If you know about the GM switch, it has a dome terminal at the front of the switch.
I put a test light to this terminal and it's not doing a damned thing.
I would have thought the terminal would have power to it, no?
I checked the wiring kit and it all seems fine. Dome light works if I run it to the battery etc, but this switch has no power coming off that dome light terminal. do you think it's a dud, or am I missing something?
thanks gents
I'm nearly finished wiring up the '54 with my Rebel wire kit, and I bought a mid fifty dome light wiring kit to add a dome light to the setup.
I bought a GM style headlight switch to make wiring up a tad easier. All works fine except when I try to dome light.
If you know about the GM switch, it has a dome terminal at the front of the switch.
I put a test light to this terminal and it's not doing a damned thing.
I would have thought the terminal would have power to it, no?
I checked the wiring kit and it all seems fine. Dome light works if I run it to the battery etc, but this switch has no power coming off that dome light terminal. do you think it's a dud, or am I missing something?
thanks gents
Fleet Mechanic
Joined: Dec 2005
Posts: 1,603
Likes: 44
I been there on this. My 54 switch took a dump in a snow storm., back to the
highway dept. garage all we could find was a new GMC. Of course its plug in
and the 1954 is terminals. So we did figure the thing out with a test light,
and all I can say there is a terminal there. If I remember find out when you
turn left for dome lite, in the area of the inst. dimmer thats where it should be.
Im talking about the reostat area.
Geez we always get called in for night snow storms never snows daytimes???
highway dept. garage all we could find was a new GMC. Of course its plug in
and the 1954 is terminals. So we did figure the thing out with a test light,
and all I can say there is a terminal there. If I remember find out when you
turn left for dome lite, in the area of the inst. dimmer thats where it should be.
Im talking about the reostat area.
Geez we always get called in for night snow storms never snows daytimes???
Cargo Master
Joined: Oct 2013
Posts: 2,580
Likes: 29
From: in a barn
Normally the GM dome light is fed 12v hot all the time and the dome light switch supplies the ground. If you are talking about rotating the light switch all the way to supply power to the dome light it doesnt, it supplies the ground. Works the same way with the jam switches on the doors.
Senior User
Joined: Oct 2013
Posts: 345
Likes: 0
From: Yorkville Indiana
Drop top is correct, you won't have any voltage at the terminal. The terminal is a ground. The light needs a hot wire (12 volt feed) at all times. When the switch is turned to turn on the dome light it creates a ground to complete the circuit.
Hotshot
Joined: Oct 2009
Posts: 16,198
Likes: 4,807
From: Burbank, WA
Be sure to insulate the dome lamp from the cab when hooking it up to power. OEM uses plastic grommet-type push in nuts to secure the lamp to the body. You can also use door switches in the same circuit that ground when opening, too.
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Laughing Gas
Joined: Sep 2013
Posts: 1,203
Likes: 146
From: Goulburn, NSW
Thanks guys.
I'll just pirate this Mid-Fifty diagram for a minute. Hope they don't mind. It's a great diagram.
Of course this setup assumes I am using the oem ford headlight switch I guess...
Where is says power, I add a constant 12v and the dome light works beautifully as it should, doors and switch works like a friggin' peach.
However, if I want to use the GM switch to turn it on, I can't
(not that that is a big deal because it has its own switch)
I guess this setup relies upon the fact that the dome light base has to be earthed thereby bypassing the gm switch earth..
I'll just pirate this Mid-Fifty diagram for a minute. Hope they don't mind. It's a great diagram.
Of course this setup assumes I am using the oem ford headlight switch I guess...
Where is says power, I add a constant 12v and the dome light works beautifully as it should, doors and switch works like a friggin' peach.
However, if I want to use the GM switch to turn it on, I can't
(not that that is a big deal because it has its own switch)
I guess this setup relies upon the fact that the dome light base has to be earthed thereby bypassing the gm switch earth..
Are we there yet?
Joined: Mar 2006
Posts: 1,098
Likes: 64
From: NW Valley AZ
You will need be a ground wire to the switch so that it could send ground to the light terminal when switched on.
I had an issue with the GM switch, the contact was not touching in the switch. Just had to give it a little bend and it was fine.
I did have to run 2 wires to the dome light. One for constant power and one from the switch for ground which is also connected to the door pins.
I had an issue with the GM switch, the contact was not touching in the switch. Just had to give it a little bend and it was fine.
I did have to run 2 wires to the dome light. One for constant power and one from the switch for ground which is also connected to the door pins.
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