What are these wires for ? 72 GMC
 

Help
Can anyone identify what these wires and plugs would be for?

72 gMC with 307 and 4 speed floor shift.

It now has a 305 and is not using these anymore. They are all on the same harness passenger side are near the firewall.

One green wire on its own with a plug and loomed

One semi thick red (power I assume) with a plug

Then one 3 wire plug with a blue, green with a white stripe , and brown with a white stripe.

Re: What are these wires for ? 72 GMC
 

The Green one would be for the temp gauge sender (should be in the head by #1 spark plug)

The other ones look like Alternator wiring.

LockDoc

Re: What are these wires for ? 72 GMC
 

Thanks for the response. I don’t know that the green one is long enough to reach over to the other side of the block by #1. I could try I guess. This would be the wire then I assume that goes to my temp gage in the dash ? Or at least did originally? I have a green wire on my thermostat housing now but again I don’t know if it’s hooked up anywhere else or it even does something.

As for the other plugs the red and the 3 wire plug yes a previous alternator connection sounds right.

Re: What are these wires for ? 72 GMC
 

Yes, for the temp gauge. Some of the later engines may have had a sender in the T-stat housing but I think the '72 was still in the drivers side head. Not sure about the Canadian models though.

There is a port by the #8 plug also but you very seldom see a temp sender in that location. Do you have a temp sender in the drivers side head by #1 plug?

LockDoc

Re: What are these wires for ? 72 GMC
 

I do yes but this is a 305 and the casting number says it’s from a 80-85 model year GM. But yes it does have a spade connector sensor there at #1

Re: What are these wires for ? 72 GMC
 

Looks to me like an old NOx system wiring that cut out vacuum to the dist until you shifted into 4th gear. Used to be a solenoid bolted to the intake and a relay on the firewall. dark green wire does look like the temp wire with the insulation and the broken metal bracket. Looks like it may have been rerouted at some point

Re: What are these wires for ? 72 GMC
 

Agree with KWMECH. Wires for TCS solenoid. The green wire is for the secondary temp sensor related to override TCS function, not for the temp gauge. The temp sensor for TCS function was between 6 and 8. So, trucks with TCS had two temp sensors.

Re: What are these wires for ? 72 GMC
 

Wow awesome info. Thanks. Ok so safe to say then now that I have an 80’s 305 and soon to be a 350 or something else I can get rid of these wires and will never need to use them again ? Where do they come from and can I unplug them from somewhere in the firewall or somewhere else? Want to clean up the engine bay of unnecessary wires.

Re: What are these wires for ? 72 GMC
 

I suggest you get yourself a wiring schematic for your year truck. Makes it simple to understand where wires go to and from...:metal:

Re: What are these wires for ? 72 GMC
 

Yes, you will likely never need them unless you like the factory original thing like some of us weirdos. The solenoid got its ground from a couple of different places, one was the temp sender on passenger side (cold temp situation), one was from the transmission (high gear situation). Those wires should be fairly easy to find as you already found most of them. Under the dash there will be a delay relay which supplies to the power side of the solenoid after I think 20 seconds. I can show you a pic of the timing relay as well as transmission ground wire if need be. The wires them selves will be taped together with some of the cowl top wires.

Re: What are these wires for ? 72 GMC
 

Wow I just posted this link about 20 minutes ago for something else. You can look up the wire colors yourself here:


http://67-72chevytrucks.com/vboard/s...d.php?t=558016