Anybody wanna help me figure out what these plugs are for?

[HMS88]

Hey everybody new member long time lurker. I need help figuring out what these wire plugs are for, if they are needed and any other helpful info. I've been scouring the forums and google but haven't been able to see a solution for myself. It appears the PO of my truck did some self wiring that I can't figure out. They added a trailer break controller that seems to be powered on, removed the emissions/smog gear. Sorry for my ignorance im still learning a lot about the truck. Anyways any help will be greatly appreciated.

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[85K304SPD]

A good wiring diagram will tell you what those wires are. I have found them on the Autozone site. You can probably find them in other places as well. Usually the plugs will only plug into one thing, so its a process of elimination. Also they usually only reach where they are supposed to plug into. Good luck.

 

[SirRobyn0]

Since this is your first post, Welcome fellow Washingtonian! I'm going to echo what Richard said, hit the wiring diagrams. It's possible someone might come along that just so happens to know what those connectors are for but probably not. I assume from the third picture they are all under the dash? Sometimes there are unused connectors depending on the options on the truck. Hit the diagrams to find out.

 

[Matt69olds]

I’m pretty sure the top photo is the plug for the factory radio speakers.

Does your truck have cruise?

You didn’t mention the year, I’m guessing probably 83ish and up?

The second photo looks like where the cruise control lever would plug in.

The 3rd pic is speed sensor. I think there is a green box somewhere that will plug into. If you have the dash cluster out im pretty sure the optical sensor bolts the the back of the speedometer, follow that harness and you will find the green box (speed buffer) that last plug should fit that box.

 

[DanMcG]

Welcome to the forums!
you can find your wiring diagrams here;

https://www.gmsquarebody.com/threads/1973-1991-wiring-manuals.14498/

 

[HMS88]

Sorry for the late response I didn't think anyone else had responded.

Since this is your first post, Welcome fellow Washingtonian! I'm going to echo what Richard said, hit the wiring diagrams. It's possible someone might come along that just so happens to know what those connectors are for but probably not. I assume from the third picture they are all under the dash? Sometimes there are unused connectors depending on the options on the truck. Hit the diagrams to find out.

Thanks for the help, yes you're correct all the plugs are under the dash. Also hello from Olympia!

I’m pretty sure the top photo is the plug for the factory radio speakers.

Does your truck have cruise?

You didn’t mention the year, I’m guessing probably 83ish and up?

The second photo looks like where the cruise control lever would plug in.

The 3rd pic is speed sensor. I think there is a green box somewhere that will plug into. If you have the dash cluster out im pretty sure the optical sensor bolts the the back of the speedometer, follow that harness and you will find the green box (speed buffer) that last plug should fit that box.

I think you have nailed the ID of the plugs. My trucks an 83, has an aftermarket stereo deck so that would make sense why that plug is not used. Also the truck doesn't have cruise I believe it was removed when the column was swapped and don't think it was operational. As for the 3rd plug I will do some more research on the speed sensor. I have two dash clusters one has the part your describing and the other does not. Really appreciate your reply!

Welcome to the forums!
you can find your wiring diagrams here;

https://www.gmsquarebody.com/threads/1973-1991-wiring-manuals.14498/

Thanks Dan I've downloaded these and have been working through them. I'm definitely not a wiring expert, I can follow the stock diagrams fairly good but I start getting lost when I get to a spot where the colors don't match up. I realize that's the point where the PO has done some modifications. I think Matt may have figured it out though.

Thanks again everyone for the help really appreciate this forum and everyone's knowledge!

 

[scrap--metal]

I’m pretty sure the top photo is the plug for the factory radio speakers.

Does your truck have cruise?

You didn’t mention the year, I’m guessing probably 83ish and up?

The second photo looks like where the cruise control lever would plug in.

The 3rd pic is speed sensor. I think there is a green box somewhere that will plug into. If you have the dash cluster out im pretty sure the optical sensor bolts the the back of the speedometer, follow that harness and you will find the green box (speed buffer) that last plug should fit that box.

Impressive

 

[SirRobyn0]

Sorry for the late response I didn't think anyone else had responded.

Thanks for the help, yes you're correct all the plugs are under the dash. Also hello from Olympia!

I think you have nailed the ID of the plugs. My trucks an 83, has an aftermarket stereo deck so that would make sense why that plug is not used. Also the truck doesn't have cruise I believe it was removed when the column was swapped and don't think it was operational. As for the 3rd plug I will do some more research on the speed sensor. I have two dash clusters one has the part your describing and the other does not. Really appreciate your reply!

Thanks Dan I've downloaded these and have been working through them. I'm definitely not a wiring expert, I can follow the stock diagrams fairly good but I start getting lost when I get to a spot where the colors don't match up. I realize that's the point where the PO has done some modifications. I think Matt may have figured it out though.

Thanks again everyone for the help really appreciate this forum and everyone's knowledge!

I'm a bit north and east of you out highway 2 and then North and East of Monroe.