Interior light, open door switch

[42Grand]

That should be the wire that hooks to to your seatbelt to send a warning buzz that your seat belt isn't buckled. Also should have a dash warning light that says seatbelt. Of couse with it not being connected you won't hear the buzz but you should still see the seatbelt light.

They had that in 77? Hmm. Interesting... Looks like I'm going to forget about it then! Ain't nobody got time for that!

 

[75gmck25]

Some optional features (like cab lights) may have been pre-wired up to a point, so that a dealer could add something later. The wiring for my cab interior lights runs up to that point in the cab near the back of the sill plate, and then up inside the driver's side post to power the dome light. When I added a bed light I was able to pull the parts and wiring from a junkyard truck and just plug in the wires at that same point. The wires should be orange (constant 12 volts) and white (switched ground).

Bruce

 

[42Grand]

Some optional features (like cab lights) may have been pre-wired up to a point, so that a dealer could add something later. The wiring for my cab interior lights runs up to that point in the cab near the back of the sill plate, and then up inside the driver's side post to power the dome light. When I added a bed light I was able to pull the parts and wiring from a junkyard truck and just plug in the wires at that same point. The wires should be orange (constant 12 volts) and white (switched ground).

Bruce

I remember seeing those wires, there were 3 total. The 2 you were talking about and this one black one. I was hoping it was for something else (later model pillar cab light switch wire) or a door plunger wire, but no such luck. I guess I could always add the plunger and repurpose that wire if I really wanted to.

 

[73c20jim]

My base 73 has no door jam switches and no overhead cab lights. My custom deluxe 73 has door jam switches and an overhead cab light.

From what I have read the jam switches control the under dash light and the headlight switch controls the over head light.

Since my overhead light is not connected I cannot confirm this.

 

[idahovette]

My jamb switch works both the under dash light and the dome light. The headlight switch works both of them ,too

 

[75gmck25]

Both switches (door and headlight) also work all the interior lights on my truck.

If you have a bed light on the back of the cab, its also on the same circuit. However, there is a 2nd switch above the seat belt anchor on the driver's side door pillar. To turn on the bed light you must have a door open or the headlight switch turned to max, and you also must have the door pillar switch turned on. If you leave the door pillar switch on all the time it will then turn on the bed light every time you open the door.

Bruce

 

[Termite_Delight]

I have an '86 GMC cab that has the switch on the drivers side and under dash light only. No switch on pass side... No overhead light.

 

[75gmck25]

My truck is a GMC with Silverado trim, so it was the most trim upscale you could get in '75.

Bruce

 

[42Grand]

My truck is a GMC with Silverado trim, so it was the most trim upscale you could get in '75.

Bruce

Was the switch above the drivers side seat belt mount an option back in 75? If not, when was it first introduced?

 

[75gmck25]

I added the cargo light to my '75, so I can't verify the location of the original switch. The '75 owner's manual provides info about turning the cargo light switch on and having the cargo light come on when you turn the headlight switch or open the door. However, there is no picture of the switch location.

My truck had only a factory AM radio, but the owners manual also has directions for adjusting the AM/FM stereo radio and fading between front and rear speakers. The rears were probably in the cab corners, but I don't know where they put the front stereo speakers. There were no mounting areas for speakers on the left and right sides of the dash in '75, and the kick panels don't have space behind them to fit much of anything.

Bruce

 

[42Grand]

I added the cargo light to my '75, so I can't verify the location of the original switch. The '75 owner's manual provides info about turning the cargo light switch on and having the cargo light come on when you turn the headlight switch or open the door. However, there is no picture of the switch location.

My truck had only a factory AM radio, but the owners manual also has directions for adjusting the AM/FM stereo radio and fading between front and rear speakers. The rears were probably in the cab corners, but I don't know where they put the front stereo speakers. There were no mounting areas for speakers on the left and right sides of the dash in '75, and the kick panels don't have space behind them to fit much of anything.

Bruce

Hmm...that's interesting! I wonder what options were really there then. If time could tell!

 

[gotyourgoat]

Another option with lights and jamb switches.

Have an 84 with no interior lights but there is one jamb switch in the driver side. It's sole purpose is to make the buzzer go off if the keys are left in the ignition and the door opens.