Switches

[mxer147]

Since the knowledge is vast here and it’s been saving me time, thank you all, please inform me what the purpose of the switch under the headlight switch? Also, the gauge bezel doesn’t quite match up with the headlight switch and opening, a PO did a dash hack so not sure if the headlight switch isn’t located correctly? I usually do a search first but wasn’t sure what that switch is called and I don’t see it labeled. Windshield wiper switch is on the column and it’s not a manual choke pull. Also, what could be the purpose of the red indicator?

 

[Doppleganger]

At the very bottom? Looks like electric brakes.

 

[rusted nuts]

What happens if You pull it???

 

[squaredeal91]

Looks like an add on. Probably not factory. Where do the wires go?

 

[mxer147]

It pulls out about 1/4”, three wires are connected to the back terminals, one goes to the red indicator, the other two go into the engine cavity. The two going through the firewall and into the engine cavity are heavily black taped and feed into the covered wire loom so not easily traced without unwrapping the tape. When I pull the switch nothing happens and no light indicator either. From the factory, did the wiper switch reside where the light switch is and the light switch was in the lower opening?

 

[Matt69olds]

With a truck that old, and lots of previous owners and modifications, who knows what it was for? For all you know, whatever the switch controlled might be long gone.

If you really want to know, carefully trave each wire until you find what it’s connected to. The problem with that approach is the half assed “repairs” or modifications you will more than likely find.

I HATE fixing previous owners wiring. It usually turns into a major headache.

 

[mxer147]

Could this switch be a trans lock when this truck was an automatic rather than a manual as it is today? I’ve noticed a few threads with trans lock switch which looks similar.

 

[PrairieDrifter]

There's something going on with the light switch. Looks like the bezel is mismatched too. What year is the truck? That's a late 70's bezel. Which switch actually makes the lights come on?

 

[mxer147]

1983 K20, upper switch is lights, lower unknown, the bezel is for windshield wiper on dash eventhough they are working at the column. The lower switch has three wires, two go through the firewall, one goes to the red illuminated near the switch.

 

[PrairieDrifter]

1983 K20, upper switch is lights, lower unknown, the bezel is for windshield wiper on dash eventhough they are working at the column. The lower switch has three wires, two go through the firewall, one goes to the red illuminated near the switch.

Probably just a really hack way for some aftermarket lights or a bad headlight switch at some point.

 

[mxer147]

I’ve been working on dash wiring yesterday evening and today since I am working on the hvac vents so I’m back to the mystery switch which I traced one wire connected to two fusible links going through the firewall and the other wire going to the block terminal on the firewall. Without the switch assembled, truck runs. Switch is heavy duty 75 amp which is now disassembled. Perhaps this was PO attempt at a kill switch for theft prevention? Thoughts? Original post shows the switch installed when I bought it. What should I do with this mess since it’s obviously charged.

 

[nvrenuf]

The part mounted to the bottom of the dash looks like a trailer brake controller.

 

[mxer147]

Yes, it’s a Kelsey Hayes brake controller which PO didn’t wire up so it doesn’t work. I’m going to test it to see if it works. Online wiring illustrations show four wires, this one only has three, missing the white wire. Thoughts?

 

[Bextreme04]

Yes, it’s a Kelsey Hayes brake controller which PO didn’t wire up so it doesn’t work. I’m going to test it to see if it works. Online wiring illustrations show four wires, this one only has three, missing the white wire. Thoughts?

My first thought is to throw it in the garbage. It is an old hydraulic actuated controller that needs to be spliced into your brake lines to function.

Apparently, these models are well known and the white isn't needed because it grounds through the case when mounted. You just need to hook up the rest of the wires as shown in your diagram and make sure that the unit is solidly mounted to a grounded metal surface.

 

[mxer147]

I found several threads which state red to positive, black to negative and blue to a resistor which my truck has so I’ll wire it up and test it. If it works it might stay, if not, it’s trash. The other switch still a mystery.