Wiring questions! Help!

[LACROMER]

So I recently bought a 83 K10 and the PO has the wiring looking like a rats nest. I'm not very good at reading wiring diagrams so that's why I'm asking for help here. I found this random wire hanging under the dash, it goes to this plug next to the steering column and there is also a wire going for the same plug through the firewall and just ends. does anyone know what these wires are for/where they go and where the plug plugs into? Thanks in advance I know wiring is complex and I'm probably not the best at explaining my issues lol :|

 

[Georgeb]

Looks like aftermarket stuff to me. Either from a radio or alarm system.

 

[LACROMER]

WTH is this?

Okay I've removed a lot of wiring that looks like it wasn't there when the truck was made but I'm confused about what this is. It was plugged into the ACCY port on my fuse panel most of it is just a cluster **** of wires but the one brown wire is running to this thing that I have no clue what it is. Any ideas?


(The mystery thing is next to the steering column)

 

[chengny]

I can't tell too much from the images, Alex. But I am gonna go with; "what is an electric trailer braking system" for $500.

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[crpntr78]

Hello, I have similar issues. I have an 85 cab (replaced a 77 or earlier cab that the PO had vin number for an 86) that was wired for dual tanks. I cant find where the fuel sender wire hooks to the firewall wire block. I have a single fuel tank. Also I have a700r4 tranny that I would like to hook back up to factory wiring but I can"t find where it gets it's power. The cab (truck) had a 700r4 in it. It has the double brake switch and the vacuum switch on the firewall.

 

[chengny]

I cant find where the fuel sender wire hooks to the firewall wire block. I have a single fuel tank.

That's because it doesn't transit the FW through the block. Trucks equipped with dual tanks have an extra grommet in the firewall to accommodate the 3 wire group associated with that option. It should be just outboard of where the accelerator cable passes through the FW:

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Control power for the 700R4 originates at the ACC section of the fuse block. There should be a BRN or BRN/WHT lead plugged into one of the sockets in that bank (5th column from the left)

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[crpntr78]

Okay thank you. Question though. My cab only has two wires exiting the firewall through a gromet. They are blue and light green and once inside the cab they run to the fuel tank switch by the ash tray. 2 wires come off that and go to the fuse block. On the outside the blue/green wires ran to a connector but it was all melted and fused together beyong recognition. No little brown wire at all. I do have a pink or tan wire with a black stripe exiting through the fuse block and travels to the right side of the cab with a connector on it. It runs through the conduit along with the wires that go to the alternator and starter. Could that be the wire I'm looking for?

Now onto the TCC lock up. I have the wiring that comes up from the tranny and hooks up to the vacuum switch on the firewall but nowhere do I find any wiring exiting the firewall to hook up to a 3 wire connector that's attached to the tranny wiring. I would assume it gets power from somewhere outside the firewall. I do have a 2 wire connector exiting the firewall just below the master cylinder with the colors that match the tranny wire but they have a 3 wire connector. I'm kinda lost. Truck didn't have cruise control. I cabbaged the tranny wiring from a salvage yard, don't remember if it came from a cruise vehicle or not. Thanks for any help you can provide.

 

[chengny]

I may be wrong that the pink wire for the sender(s) uses the same grommet as the control wiring for the switching valve. I was too lazy to go out to the truck and check - and I still am. But look at the images below they might help you locate the pink sender wire. If you can locate the pink as it enters the loom, you should be able to trace it back to where it penetrates the firewall.

This shows all the wires that go to the rear of the truck as they enter the loom:

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Here is the loom as it heads back:

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Here is where the pink sender wire comes out of the loom. What you see is an extension that was spliced on to the normal (single tank) sender lead. That runs over to where the transfer valve was located. This view is from behind the cab (bed off) and above the LH frame rail:

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[chengny]

I do have a 2 wire connector exiting the firewall just below the master cylinder with the colors that match the tranny wire but they have a 3 wire connector

Looks like the wiring in the engine compartment is set up for a 4WD truck and the cab is from a 2WD truck. Here are the two wiring diagrams:

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See if the colors match up. We'll figure out how to make the TCC work later. Right now I have to go do something that looks like work or my wife will kill me.

 

[crpntr78]

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Here are all the wires in question. Thank You.

 

[crpntr78]

You are correct in that the cab is from a C10. I will look again for the suggested wire(s) Thanks

 

[crpntr78]

Got the gas guage to work. It was the pink/black stripe wire. I traced it back to the fuse block. Thanks for the help. Now onto the tranny wires.

 

[chengny]

Here's the problem:

The wiring harness in the engine compartment (the 3 wire group) is set up for 4WD. The cab side of the harness (the 2 wire group) is set up for 2WD.

The primary difference is that a 4WD TCC control system incorporates a 4WD relay. The relay disables the TCC unless the transfer case is in either 2WD or N.

But that circuitry also requires that the transfer case have a 4WD lock-out switch which activates the 4WD relay. Also, not necessary but useful, are a couple of lamps (4WD indicator light on the dash and transfer case shifter illumination).

On the other hand, the only component on the cab side of the 2WD circuit is the brake switch (same part as used with 4WD).

So there are several ways to reconcile the differences between the two dissimilar circuits (that I can think of). Here they are - ranked from hardest to easiest:

1. Locate/purchase/install all the required parts to allow for the 4WD lock-out feature (relay, relay base, TC switch - and the indicator/illumination lights) and fabricate your own 3 wire harness to allow it to link up with the engine side.

2. Find a complete 4WD set-up (cab side) at a junk yard, carefully remove it and install into your cab.

3. Leave the cab wiring as is and just remember to take the transfer case out of 4WD if you intend to drive faster than 45 MPH (the approximate speed at which the TCC engages). Requires an easy modification to the engine side harness (cut the LT GRN and the BLU/BLK then splice them together). The brake switch will still disable the TCC as designed.

The light green going back into the cab is to the test connection and isn't necessary.

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I would pick option 3.

 

[crpntr78]

Now it all makes sense. Thank you very much for the info.

 

[crpntr78]

Good morning, Here's another question. I'm wanting to change over from a 2 light to a 4 light front end. Outside of having to get a 4 light core support and wiring harness is there anything else I will need to make this conversion? Will the fuse block accomodate the extra headlights? How about the switch? Trying to get all my ducks in a row before starting this project. Thanks for any input.