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Go Back   6066 (1960-1966) GMC Truck Club > 6066 GMC Truck Club Forum > Interiors, Dash, Lights and Electrical


Interiors, Dash, Lights and Electrical Everything Inside

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  #1  
Old August 10th, 2022, 12:36 AM
Scrapcan Scrapcan is offline
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Default headlight switch wiring for 1963

ok slowly muddling my way through the issues. I know the wiring is all good, check all wires and harnesses. Long story but it has been done, harnesses have been out of the truck, opened up, visually verified, continuity verified, wires/insulation verified, and wiring is as it should be.

The issue is that I put in a new headlight switch from Napa and I do not have gage lights or tail lights when the headlights are on. They work in the first detent for the tail and markers.

What should I be looking at here? Bad new switch? Do I need to make a modification similar to the fix to have tails and markers on at the same time? would that make them not work if I did the mod shown on Jolly’s site?

I will pull the switch and open it up, since it is electrical I cannot take it back anyway.

Any help is appreciated

Last edited by Scrapcan; August 10th, 2022 at 02:28 PM.
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  #2  
Old August 10th, 2022, 02:36 PM
James James is offline
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Default Re: headlight switch wiring for 1963

If you have no gage ("Inst. LPS" on the wiring diagram) lights, the gage light power goes through a 3 amp fuse (label "Panel LPS" on the fuse block) after it leave the headlight switch.

Before you take the switch apart. Plug the connector into the switch. Take your meter and back pin the connector and check for power on all of the wires in each of the positions. Be sure to write everything down (wire color, voltage, and switch position). Then you can post it here. All of the power come through a 15 amp fuse label "Tail-Stop-Dome LPS" (which include the power to feed "Inst. LPS" circuit and fuse).

Note: With the headlight switch removed from the dash you will need to provide a chassis ground to the metal part of the switch to be able to turn on the dome light. Dome light ground through the switch body to the dash.

Last edited by James; August 10th, 2022 at 02:41 PM.
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  #3  
Old August 10th, 2022, 10:08 PM
Scrapcan Scrapcan is offline
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Default Re: headlight switch wiring for 1963

I have ordered the wiring diagram and waiting on delivery. a nice hard copy in hand is handy when working on this instead of digital file. until it gets here I am asking for help from the forum, and I appreciate all the help I am getting.

Here is a picture of the old switch I put pin numbers on, new switch looks the same other than no issues as the old switch. old switch had been apart before with problems.

pin 1 is white(natural?) and is front markers through the front-left firewall connector

pin 2 is light blue and is dimmer for headlamps

pin 3 is white (natural?) is dome light (is this the ground side of dome light circuit?)

Pin 4 I need to verify the color but think it is red and 12v+ unswitched from the front-left firewall connector

Pin 5a is black and is rear tail lights through the center-firewall connector

pin 5b open no wire connection

pin 6 is orange, double wire to connection, not sure but I think this is 12v+ to the fuse panel and to the stop lamps switch.

pin 7 is dark green and is instrument lamps through fuse panel?

with switch in rest position ( all the way in) 12v+ on pin 4 and pin 6. front and rear turn signals and brake lights work

turn switch to dome light position and puts 12v+ power on pin 3 and power at dome light fixture. turn signals front and rear and brake lights work

with switch in position one ( pulled out to first detent, have power to pin1, pin5 ( a and b on old switch, need to test new switch), and pin 3 if in the dome side of switch. tails on, markers on, instruments lamps on and dimmer works for instrument lamps. turn signals front and rear and brake lights also work.

with switch in position 2 ( pulled out to activate headlights. have headlights both dim and bright. no tails, no markers, and no instrument lights. Have the power to dome light if switch turned to that position. Turn signals front and rear and brake lights work. Need to test power to 5(b) and pin 7 on new switch.

the old switch had a bar between pin 5(a) and 5(b) so with the switch in either position and switch in position 1 or 2 ( tails and markers position 1 or headlights position 2) the slider will have power to pin5(a) and 5(b). this would make tails work in both switch positions. Pin 7 is also fed power on the connector bar from 5(a) and 5(b) on the old switch thus powering to instrument lamps.

the old switch also disconnected pin1, as discussed on Jolly's site and as designed, when the switch is pulled out to position 2 (headlights on). need to test this on the new switch

as noted above, I will check the new switch again tonight for continuity in the different positions
Attached Images
File Type: jpg HDLS-pinout.jpg (1.73 MB, Multiple views, 3 clicks)

Last edited by Scrapcan; August 10th, 2022 at 10:22 PM.
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  #4  
Old August 10th, 2022, 10:12 PM
Scrapcan Scrapcan is offline
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Default Re: headlight switch wiring for 1963

forgot to mention all fuses checked, known good.
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  #5  
Old August 10th, 2022, 10:44 PM
James James is offline
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Default Re: headlight switch wiring for 1963

I have a 1962 and a 1964 wiring diagram. I don't have a 1963 wiring diagram. And comparing the 1962 to the 1964 they are different, so the 1963 may also be different than the other two.

I guess we'll have to wait until you get your wiring diagram.

Last edited by James; August 10th, 2022 at 10:58 PM.
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  #6  
Old August 11th, 2022, 12:35 AM
Scrapcan Scrapcan is offline
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Default Re: headlight switch wiring for 1963

I will post what I find if I get a chance to work on it this evening.
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  #7  
Old August 11th, 2022, 07:13 PM
Scrapcan Scrapcan is offline
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Default Re: headlight switch wiring for 1963

I think the 1963 is odd ball, but might be the same as 1962. I think 1964 is different.

Good news is i think I found my issue. Here is a picture of wire colors at headlight harness plug
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  #8  
Old August 11th, 2022, 07:15 PM
Scrapcan Scrapcan is offline
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Default Re: headlight switch wiring for 1963

I believe this is my issue and it is manufacturing issue. Not good contact on the slider. As a side note, instrument lamps, markers, and tails worked on position one because i did the tail/marker mod shown on Jolly’s site!

My fix was to cleanup the plastic slider pockets of flashing from casting and duburred the metal slider contacts.

Hard enough to diagnose without out having new parts with issues.
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File Type: jpeg EDDC581D-57E7-491A-A62B-E3197B0AB16C.jpeg (4.22 MB, Multiple views, 2 clicks)

Last edited by Scrapcan; August 11th, 2022 at 07:33 PM.
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