75 chevy wiring issue

[scotty17509]

So i finally got my truck back together after installing a new exhaust, an MSD ignition and new intake. Anyway while running the msd wires into the cab i accidently ran a screw through the power wire for the msd box. So not knowing, i hooked the cable to the battery. Now the heater fan does not come on and the gas tank switch doesnt switch tanks. I checked all the fuses i could find and obviously fixed the wire but cant get it working. Does anybody know which wire i may have burnt out or what i should check?

[N2TRUX]

Anyone?

[keith61760]

Looking at my 77 wiring diagrams, the only thing I could think of is a splice point. I do remember when I took my wiring harness out of my truck there was a nasty splice that had 6 wires with a cheesy crimp that look ratty. It was a group of red think wires. Did you splice into a pink wire with black stripe? If I remember correctly that was the power wire color for mine.

[scotty17509]

Thanks for replying. No i didnt splice into any wires for the msd box. It is ran directly to the battery. Im thinking im going to go down the the wrecking yard and grab a relay for the fan and look through what wires i can on a truck without an engine. What would really help is a wiring diagram of the truck. Would you be able to post your 77 diagram?

[keith61760]

Originally Posted by scotty17509

Thanks for replying. No i didnt splice into any wires for the msd box. It is ran directly to the battery. Im thinking im going to go down the the wrecking yard and grab a relay for the fan and look through what wires i can on a truck without an engine. What would really help is a wiring diagram of the truck. Would you be able to post your 77 diagram?

It may have still shorted the factory splice. I will figure out how to post it. It is pretty detailed and will be a pretty big file.

[scotty17509]

Originally Posted by keith61760

It may have still shorted the factory splice. I will figure out how to post it. It is pretty detailed and will be a pretty big file.

Which factory splice do you mean? Any luck on getting that sendable? I would really appreciate it if you could do that. Or maybe you could send it through an email? Scotty17509@hotmail.com.

Thanks!

[ron350]

The blower motor 12 volts comes from the ignition switch through a 20-amp fuse.
The fuse is located at the top right corner of the fuse box.
First thing to do is check and see if you have 12 volts at both ends of that fuse with the ignition switch turned to the run position.

Yes it would be nice to have a good one page wring diagram on line.

[fixit-p]

Here's some diagrams which may help. If you ran the msd wire direct to batt your problems are unrelated to your short to ground troubleshoot each circuit starting at the fuse as mentioned by ron350.

[keith61760]

Originally Posted by scotty17509

Which factory splice do you mean? Any luck on getting that sendable? I would really appreciate it if you could do that. Or maybe you could send it through an email? Scotty17509@hotmail.com.

Thanks!

Scott-Check your email.

[keith61760]

Another thing to check is loose blade connectors near your fuse block. I was just thinking about it and on my 77 stock I had a few in there that were stock to the best of my knowledge. There was one that went to the tank switch in my truck.