Here’s another switch that I don’t know the function of off the 40 harness I’m working on. (1 Viewer)

[electroapprentice]

This is second day where I’m asking for some advice/info on this 69’ 40 harness because I know somewhere out there is someone who’s had something like this on their hands before. Today I’m following that aftermarket breaker to see where it leads from a glance the wires look like the stock headlight wires. I took the dimmer switch off after my boss looked me in the face and said this year didn’t have dimmer switches pshhh yeah sure then what dis? Anyhow I followed the wires and one of them led to this thing which I think is an aftermarket headlight switch. The switch connects to that breaker via one 12 ga grey wire, to the instrument panel through a multi wire connector (not the high beam indicator), to the fuse box and to the switch that was on the driver side floor board that I think was the dimmer through another 12ga wire this time dark blue. Y’all let me know what this is because before I started working on this truck I thought it was the wiper switch but it already had one, and my boss told me that what I thought was the dimmer switch was actually the only headlight switch so I’m a little all over the place right now with misinformation and miscommunication.

 

[electroapprentice]

Big news on that switch, it’s connected to the instrument panel yes but more interestingly than that it’s connected to the turn indicators.


There’s it’s evil blue wire that looks the same as 12 others throughout the harness lol.

 

[charliemeyer007]

I think it looks like a heater switch, who knows what the op's used where.
If you haven't blown up the correct factory wiring diagram to at least A size, now is a good time.

 

[B y r o n]

I picture of where is was mounted on the dash might give a clue as to what it was used for.

 

[kunzma]

I will guess a hazard switch.

 

[peesalot]

That swith should be a pull out to turn on with two positions. The lead you refer to as going to turn indicator is probably the parking lamp as the 1st pull turns on park lights which IIRC run thru blinker/brake/hazard so they may not really be turn indicator, more investigation, thats where the hot test jumper comes in handy. That headlight switch should have been put on 1 of those relays as opposed to running straight off breaker, sounds like since they had constant power at headlight switch they powered cluster from there as well. The part you need to work out is from headlight switch to foot beam changer then to headlights, find & label the blinker bulb leads at all four corners, same for brake lights, same for turn indicators, that blinker/brake/hazard flashed the rear brake lights for blinkers IIRC, thats the hardest part to figure, the rest is easy.

 

[electroapprentice]

Big news on that switch, it’s connected to the instrument panel yes but more interestingly than that it’s connected to the turn indicators.


There’s it’s evil blue wire that looks the same as 12 others throughout the harness lol.

View attachment 3534530

Did some research and turns out I was wrong about it being connected to turn indicators it’s actually connected to the dash lights. It is a light switch. My assumption is that it turns on the running lights and low beams then the floor switch can turn on the high beams.

 

[electroapprentice]

That swith should be a pull out to turn on with two positions. The lead you refer to as going to turn indicator is probably the parking lamp as the 1st pull turns on park lights which IIRC run thru blinker/brake/hazard so they may not really be turn indicator, more investigation, thats where the hot test jumper comes in handy. That headlight switch should have been put on 1 of those relays as opposed to running straight off breaker, sounds like since they had constant power at headlight switch they powered cluster from there as well. The part you need to work out is from headlight switch to foot beam changer then to headlights, find & label the blinker bulb leads at all four corners, same for brake lights, same for turn indicators, that blinker/brake/hazard flashed the rear brake lights for blinkers IIRC, thats the hardest part to figure, the rest is easy.

I’ve labeled the blinker and brake at all four corners however not the hazard because idk if this thing had the rear lights even connected, I appreciate all the info this will surely help me move things along. By the way what is IIRC?

 

[charliemeyer007]

If I Recall Correctly In My Humble Opinion

 

[45Dougal]

I think it looks like a heater switch, who knows what the op's used where.
If you haven't blown up the correct factory wiring diagram to at least A size, now is a good time.

It's a while since I was an apprentice, but I remember that sometimes you had to learn the hard way.
There's a lot of information buried in that old harness, but it's easy to think that you can keep it all in your head and do it faster... except you can't.
Just go through it methodically and capture each wire, switch, light, and doodad on a DIAGRAM.
Slow and steady wins the race.
Then, and only then, will you have the information you need to fix this thing properly, whether it's a truck, jet fighter, submarine or spacecraft, it all starts with a diagram.

 

[electroapprentice]

It's a while since I was an apprentice, but I remember that sometimes you had to learn the hard way.
There's a lot of information buried in that old harness, but it's easy to think that you can keep it all in your head and do it faster... except you can't.
Just go through it methodically and capture each wire, switch, light, and doodad on a DIAGRAM.
Slow and steady wins the race.
Then, and only then, will you have the information you need to fix this thing properly, whether it's a truck, jet fighter, submarine or spacecraft, it all starts with a diagram.

This morning I’m reading this in shock because last night I was laying in bed and after weeks yes weeks of dealing with this harness for six hours a day everyday I lay down and all I think about is wires lol, I thought I was a genius when I had an epiphany about getting a journal and sketching out each components circuit. Right now I’m breaking down this harness piece by piece starting with each component and their own functions and circuits, thank you everyone for the info and great advice.

 

[pjohnson]

I'm surprised no one has provided this link to Coolerman's site:

Schematics

www.globalsoftware-inc.com

 

[peesalot]

I just looked at the dia. in the link posted above and I'll be , there is a dimmer switch, who knew, I would print that and use highliter same color as wires in truck to line out each wire or device then start checkin em off as you verify wires in veh match dia. , that dia. is easy to read and really sorts things out/ answers ?'s.

 

[pb4ugo]

I'm surprised no one has provided this link to Coolerman's site:

Schematics

www.globalsoftware-inc.com

Someone did in his original thread.

 

[electroapprentice]

I'm surprised no one has provided this link to Coolerman's site:

Schematics

www.globalsoftware-inc.com

You are a hero to me right now and also mark too, I have that diagram printed but all the words are so blurry so I’ve been doing what I can with a 71 diagram, much appreciated.