View Full Version : Engine wont shut off after alternator install

05-11-2015, 02:40 PM
I am quite new to the classic car club so please excuse my ignorance. I recently purchased a 1962 Thunderbird and after 3 months the alternator (GM one-wire) stopped working and required replacement. So, I purchased a Powermaster one-wire unit(#8-47141) and replaced the old GM with it. After running the wire from the alternator to the starter solenoid, I started the vehicle without any problems. The alternator was producing energy and registering 14.7 V on the voltmeter which was good. With a big smile on my face, I went to go turn off the vehicle to find out that the vehicle will not turn off despite me pulling the keys completely out of the ignition. Obviously the alternator is feeding into the ignition circuit somehow, but my electrical knowledge is not strong enough to troubleshoot the system, hence I am looking for help. The summary of my problem is listed below and any help would be greatly appreciated:

- 1962 T-Bird with a one-wire alterantor
- Replaced alternator with a Powermaster one-wire unit
- Mounted and tested the alternator and it was producing power
- After wiring the alternator the vehicle would not shut off
- I took the battery lead off in order turn off the vehicle
- I disconnected the alternator wire from the starter solenoid and the vehicle turns on and off with the key without a problem

Please help!!!


05-11-2015, 02:57 PM
Many of our members successfully use a 1-wire. Personally, I don't like them but this is YOUR post, not mine.

Simply put, a 1-wire connects to the battery (POS post). Your key switch also connects to the battery. You connected your alternator to the ignition circuit instead of the battery circuit.

For now, I will assume your key switch is not broken. If it is, many vendors sell new ones.

Try other devices that only operate with the key, like your turn signals, radio or heater fan. If either stays on with the key off you may have a broken key switch. If they turn off as they should, you have mis-wired your alternator into the ignition circuit.

Why are you buying expensive 1-wire alternators when you could have an OEM alt that outputs over 100-amps for about fifty bucks? Bone yards throw them out daily and all alternators built in the past few decades have internal regulators. 1-wire alts don't start charging until you step on the gas because they don't have a 'sense' wire to know when your key is on/off. Normal alts charge at idle speeds (like modern cars). - Dave

05-12-2015, 12:59 PM
Thanks Dave. I agree with you regarding the one-wire alternator being expensive, but my knowledge is pretty limited and the summer is upon us so I didn't want to waste any more time :) Also, I actually ended up removing the wire from the solenoid and connected it directly to the positive terminal of the battery and that solved the problem. I am almost certain that the wire originally was connected to the battery side of the solenoid so I don't understand why the ignition was not working when I had the alternator connected directly to the solenoid.

05-13-2015, 03:10 PM
1962 Ford cars had plug-in connections except for a few. The Starter Motor Solenoid was one area with post connections.

I'm glad you got your wiring to work but now I am questioning the rest of your original wiring. Do you have a shop manual for your car? If so, you need to understand what wires are attached to the Starter Solenoid and what they do.

It is very easy to put a wire on the wrong terminal, in fact I have done it myself. Now, I take pictures before I start. What bothers me is, the wire coming from your alternator is huge. Where was it connected? - Dave