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Old 03-29-2020, 08:02 AM   #1
KevinK7
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Brake Light Wiring Question

My question is, "What path does the 12V follow, from the brake light switch(white wire) to the brake lights?"

On my 68 C20 Utility, the wiring has been 'sliced and diced' in many places, one of which is the white wire from the brake switch was CUT from harness and routed straight back to the (upper) brake lights on the utility body. Noting the Utility body has an Upper set of lights (as noted are BRAKE only), and a lower set that properly function as Tail/signal lights.
I'm trying to get the wiring back in (relative stock) order so I'd like to RECONNECT the white wire from the brake switch to the (original) section still in the harness which routes to the curved column connector.

Following the white wire through the harness to the turn signal switch, the attached pic is what I come up with, noting the 'triangles' are in the center position (ie no turn signal).
Am I correct in that the 12V from the brake switch gets to the contact (labelled "X") then through the (RED triangle) "wiper" passes to the other two points of the triangle, ...to the Left and Right tail light wiring eventually to the Yellow and DkGreen wires (respectively) of the rear light harness?

In general, can someone confirm the contact specifics? (ie is the red triangle used for BRAKE lights, and BLUE triangle contact for DIRECTIONALS?

I believe the above to be true, but hoping someone can confirm.

Thanks in advance for any information,

Kevin

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Old 04-10-2020, 08:02 AM   #2
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Re: Brake Light Wiring Question

OK, after a bit more digging and chasing wires, I'm pretty sure I'm looking at the contacts in the switch (above) correctly.

To add a bit more info (for anyone else who may stumble upon this thread) The following is the sheet from a new Turn Signal Switch I received, it details very clearly what color wires come from the column to the halfmoon connector that plugs into the dash harness.
Also shown is the original halfmoon connector from my truck (DateCode D 8 67), simply to show the wire colors all match that of the new switch harness/connector.

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Old 04-10-2020, 08:50 AM   #3
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Re: Brake Light Wiring Question

Kevin,
Did you get this sorted out? I just chased down all the lighting on my 67 so this is still a bit fresh on my mind.

I finally got all mine worked out and even got the hazard lights working when I got the correct flasher relay. Someone in the past had installed too small a fuse and the wrong flasher.

Being somewhat sequestered at home gave me the extra time and patience required to get it all going.
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Old 04-10-2020, 08:58 AM   #4
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Re: Brake Light Wiring Question

Great information and timely. Thank you.
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Old 04-11-2020, 07:39 AM   #5
KevinK7
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Re: Brake Light Wiring Question

Quote:
Originally Posted by 67C10Step View Post
Kevin,
Did you get this sorted out? I just chased down all the lighting on my 67 so this is still a bit fresh on my mind.

I finally got all mine worked out and even got the hazard lights working when I got the correct flasher relay. Someone in the past had installed too small a fuse and the wrong flasher.

Being somewhat sequestered at home gave me the extra time and patience required to get it all going.
First, Thanks for the reply, I believe I have the correct understanding, but I haven't yet made the repairs so I'm open to whatever info you can share. I'm really trying to confirm that the white wire from the brake switch (which becomes the black/white wire in the turn signal harness does in fact end up feeding 12V (through the turn switch contacts...........to the left/right rear.

I believe they start at the turn signal switch (as in my initial post) and then to the (halfmoon) turn signal switch connector they are the Black/Yellow and DarkGreen wires (positions 5 and 6 in the photo of the sheet in my last post). I believe, from there that the harness side halfmoon connector has the Yellow and DarkGreen wires corresponding to positions 5 and 6 of the turn signal harness halfmoon connector.
Just to comment, since my truck has the Utility body on it, the rear light wiring was modified quite a bit so I don't have a lot to go by.

The main reason why I went so 'deep' into the turn signal switch contacts themselves, was because the white wire from the brake switch (that would normally run to the turn signal switch) was cut ....and a new wire was run to the utility body, to a second set of lights that was added to it.
Not to get drawn out on this (but to give the full picture), the utility body came factory with only two (lower) round lights. At some point in time, two (upper) lights were added. The uppers were(are) wired as BRAKE only (fed from the CUT white wire from brake switch), where the lowers are the directionals. My hope/plan is to wire upper and lower to function both as directional and brake. ...and I do have heavy duty flashers planned.
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Last edited by KevinK7; 04-11-2020 at 07:56 AM.
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Old 04-11-2020, 01:47 PM   #6
Andy4639
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Thumbs up Re: Brake Light Wiring Question

If all your wanting is to find the right wires then take the housing out of the bed and with the brakes applied check with a test light and see which wire is feeding it. Do the same on the housing that is for turn signals. Then just run each wire to the other housing as long as you have double element bulbs in each housing.
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It sucks not being able to hear!

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After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.
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Old 04-11-2020, 06:02 PM   #7
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Re: Brake Light Wiring Question

I removed my turn signal switch from the circuit to make sure all my wiring and grounding was correct. I got tired of using the meter so I pulled the battery from my lawnmower and made me up some leads for it with alligator clips. Put a 7.5 amp fuse in the hot side just in case though.

I grounded the negative side of the battery and then connected the positive to the various connections on the outgoing side of the half moon connection and checked my lights. I am sort of anal retentive and when I repaired my intermediate harness I used yellow, green, and brown wires to match. That way if when I plugged my turn signal switch back in if everything didn't work as it did before I knew the switch needed attention as well.
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Old 04-11-2020, 10:16 PM   #8
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Re: Brake Light Wiring Question

Thanks again for the replies...
I got the new Turn signal switch installed earlier today, and worked through everything, and it looks like I'm in business. Brake lights work, directionals work, hazards work, etc. I will test tomorrow having both sets of rear lights in the circuit for brake, directional and if that works, then I'll rebuild the rear harness and be done with this phase.
Thanks again,

Kevin
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Old 04-11-2020, 10:32 PM   #9
Andy4639
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Thumbs up Re: Brake Light Wiring Question

For your question on path. orange wire on the stop light switch is feeder form the dome light hot feed.
White wire goes to turn signal connector and up into the steering column to the turn signal switch. When you put on brakes the Dark green passenger side wire and the yellow drivers side wire will make the brake lights come on.
If you pull the light switch out 1 time that feeds the brown wires to all the rear lights for tail lights and side markers if you have them.
Light green is back up lights. The black wire is for the horn relay and it grounds through the steering shaft when you apply the hand pressure to the horn button.
The purple wire supply the path to the flasher.

Now if the right turn signal is on the switch brakes the contact form that side and it goes through the turn signal flasher to blink. Same thing if you do left side. The dark blue (right side) & light blue (left side) go to the front turn signals.
Now as far as the turn signal switch itself I have never looked at it that closely as in your picture. So I can't really say but yes it makes are breaks the connection's depending on how it is set.
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Seeing the USA in a 71


Upstate SC GM Truck Club
2013,14 and 2016 Hot Rod Pour Tour


http://upstategmtrucks.com/



Get out and drive the truck this summer and have some fun!
It sucks not being able to hear!

LWB trucks rule, if you don't think so measure your SWB!
After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.
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