I am brand new to this forum and here out of desperation. I have recently rebuilt the motor in my 1974 corvette 350 ci, 4-speed manual transmission, with A/C. Now I seem to have an electrical short that drains the battery down with the key in the off position, the wiper motor doesn't work, the ventilation blower doesn't work and the a/c relay trips when the battery is connected. I had no electrical problems prior to pulling the motor and transmission and have not found any damaged wires.

Does anyone have a complete electrical drawing specific for a 1974, manual 4-speed, with air conditioning I can view or where to download one? I have a 1976 model generic electrical diagram in one of my manuals but it does not show some things, like the Transmission Spark Control relay.

Any thoughts on what to check? I'm running out of ideas.

Thanks

 

Scroll down to the bottom of page 3 in the general section and there is a member called "papwana" who emails out electrical diagrams. i think the name of the post is "68-82 electrical diagrams" . . . .

 

Here's how I would go after this.
Pull ALL the fuses. If anything (stereo, alarm, whatever) is hotwired to the battery disconnect it.
Disconnect the alternator (+) lug.
Disconnect the starter (+) lug
So now, in theory, NOTHING is connected or powered up.
Set your ammeter on 10 amps, plug the test leads into the correct plugs, make sure your ammeter fuse isn't blown...
Leaving the negative lead on the battery terminal, put your ammeter between the positive post and the positive battery cable.
gradually switch it down to milliamp range. It should read zero all the way down. There should not be even 5 or 10 milliamps of draw.
If there is, gonna have to figure out where its getting power FROM.
Reconnect the alternator and re-check the draw. Don't blow your ammeter fuse! Switch it back up to 10A range!
Reconnect the starter and recheck the draw. Are there accessory wires coming off the starter lug?

Turn OFF the lights, fan, wipers, all accessories and start putting fuses back in, one at a time. Check for a draw after each one.
I don't know what you mean by "AC relay trips." You mean clicks, or it's snapping the compressor clutch?

I own a 68 and power to the fuseblock, etc comes from the starter, through a fusible link, to the horn relay, and from there to the fuseblock and everywhere else. Alternator
output also joins up at the horn relay. (Who the hell @ chevy decided THAT was the best place to distribute power from?

I'm not sure where power is "distributed" on a '74

The laminated Willcox schematics are invaluable. I'd need to consult a wiring diagram before I could offer you further advice, but in general, what I do is pick ONE symptom (no wiper, no blower, ac relay) and diagnose THAT, and the
others usually get diagnosed or cured in the process.

If you didn't even know that your ammeter HAD a fuse or how to check it. (pull the fuse out, check it on ohms) you might want to get an auto electrician to run this drain down for you

GL

 

Check the wire's at the starter, there is a BLACK ground wire that should be connected to a starter or bellhousing bolt.
It sometimes gets connected in error to the battery positive post.

Basic '74 schematic:
http://www.keystonestatecorvetteclub...tte%201974.pdf

 

Yea, this was also my first guess. Second guess ground at horn relay..

 

 

The other area of wiring where things can go wrong is the bundle at the starter with 'fusible links' included. Lots of misinformation out there. You really need to CAREFULLY check out how all that wiring is being routed. A 'dead-short' can be created by mis-wiring in that location. Also, a bad fusible link can prevent power from getting to other systems.

 

Any progress?

If your connections at the starter/solenoid got crossed good chance the fusible link there got melted.

I recommend replacement with a MAXI fuse holder, etc. But NAPA does have FL wire for sale.