Re: Need help with gauge wiring
 

My truck is a "brand C", and I couldn't find a GMC wiring diagram, so some of this is semi-guesswork. The dark green wire goes through the engine harness connector on the firewall, so start looking for it there, and then you can follow it to wherever it ends. If you can't identify the engine harness connector, look for the one that has wires going to the starter solenoid.

Ray

Re: Need help with gauge wiring
 

After looking at your pictures, I think the answer I gave you isn't the one you are looking for. In the first pic, is the round thing with wires coming out of it the instrument cluster connector? And are you saying the other end of the green wire is just hanging free and not connected to anything?

If yes to both, the quick and dirty fix: Extend that green wire, run it though any convenient hole in the firewall, and connect it to the temp sender.

The "correct" fix: Find the green wire on the engine harness firewall connector. On the cabin side of the firewall, run a new wire from that terminal of the firewall connector to the cluster connector. On the engine side, find the green wire and see if it is long enough to reach the sender. If it isn't, replace the wire with a new one.

If the above still isn't what you are looking for, please tell me what you need to know.

On the second pic, I have no idea what I am supposed to be looking for, and the pic is too fuzzy to see much detail.

Ray

Re: Need help with gauge wiring
 

Ray you're dead on. The wire is broken and I can see both ends under the dash. I can't see where it comes out into engine compartment. That's what I need a pic of. I want to test the wire to see if there is contunity before I repair under the dash. So I need pics of where the sender is located and where the wire comes through firewall

Re: Need help with gauge wiring
 

Ok, the sender is easy. You already found where it goes. That's the place where the mechanical gauge is installed now. In other words, whoever installed the mechanical gauge removed the sender, so you need to get a new one.

For the wire, find the firewall connector. If GMC is like Chevy, it will be the one that has wires going to the starter solenoid. If nececessary, unwrap the connector end of the harness so you can see the color of the wires. You already know you are looking for the green wire, so follow it until you reach its end. On the cabin side look for the same terminal that the green wire is connected to on the engine side and connect your cluster wire to that one. That's all you need to do. As we rocket scientists like to say, "It's not rocket science."

Here are some Chevy wiring diagrams which might be of help.
http://www.64moneypit.pages.qpg.com/...ucks/id12.html
If anyone knows where GMC diagrams are, please be kind enough to post a link.

Ray

Re: Need help with gauge wiring
 

I told you I'd forget! I got tied up with my steps this weekend and didn't think about anything but a shower and sleep afterward. I'll take some pics today.

The PO might have clipped that wire because the new senders don't run well with the old gauges. You have to put a resistor on them. See here for how I did it if you're going with the a NAPA sending unit. http://6066gmcclub.com/forum/showthread.php?p=47576
They're pretty cheap too so its an easy fix.

Re: Need help with gauge wiring
 

Ok amigo, here's the wiring trail for both wires. Click for bigger pics.

The brown heater wire runs from the switch there on the outside of the wire highway (taped up wires) to the dash, then down to the fuse box like someone else said.

http://windypix.com/?dm=I0RP.jpg




It ends up at the box and plugs into the side of the heater fuse thingy with a black or brown plug. Mine is here on the wrong plug, yours should be one lower than this.

http://windypix.com/?dm=JCUP.jpg




Ok, now the sending unit wire. You already know it ends on the sending unit by the top water hose off of the radiator. You can get those at NAPA for a couple of dollars.

It starts behind the dash in the wire plug.

http://windypix.com/?dm=68SX.jpg




This is a weird pic, but it's looking up between the radio and the dash cluster.

http://windypix.com/?dm=9P31.jpg




Then it runs over behind the heater, hiding like a little girl.

http://windypix.com/?dm=2QJ5.jpg




I shoved my phone up there and got a pic anyway. Take that Engineering department!

http://windypix.com/?dm=QRPJ.jpg




It comes out of the firewall heahh, behind the coil.

http://windypix.com/?dm=L0CN.jpg




Then meanders down past the starter heahhh

http://windypix.com/?dm=NYAD.jpg




Then comes out Neahhhh with the alternator wiring (or gen if you have one). It's still dark green. And that's it. From here it just runs to the sending unit and plugs in. Tada!

http://windypix.com/?dm=MM7B.jpg





*disclaimer: Please don't blow yourself or your truck up by following my advice. It's probably all wrong anyway. :lolflag:

Re: Need help with gauge wiring
 

What you need is a maintenance manual or operators manual, they both have wire diagrams in them. check eBay. look for manual staring with 64....

Re: Need help with gauge wiring
 

Dude! You're the man!

Re: Need help with gauge wiring
 

Does anyone have the part number for that NAPA temp sending unit?

Re: Need help with gauge wiring
 

Yeah its in my build thread at the link I posted. Part number ECH TS6469
http://6066gmcclub.com/forum/showthr...7694#post47694

About 11 bucks.
Dont forget a resistor.