Three times today my car would not shut off with the key.

With the engine running I pulled the battery ground..car kept running. They I pulled the battery positive.. car kept running.



Now I have been running a 12V GM alternator for the last year and once in a great while this would happen. i would reach under the dash and wiggle the wiring loom from the switch and I could get the car to shut off. Well not now.



The car is not using the wiring loom from the regulator to the alternator. I took it off. I have a one wire alt. and the wire from the alt. goes direct to the solenoid. Again I did not have this problem but twice last year. I have removed the bulb from the gen light gauge as it would stay red while driving. I did this last year. Also the old voltage regulator is still wired into the loom. I only disconnected the generator portion as it was no loner needed.



I know there is a solution without going to a new wiring harness. I couldn't find the old thread I read a couple years ago about this problem.



Please help. As you must have already come to the conclusion, as I have that the alt is back feeding the ignition but where?



Jim

  Jim Rowe Elkhorn, NE

fourth post of the starter solenoid? (resistor bypass)

 
 Steve Metzger       Tucson, Arizona

Jim sounds like your back feeding to the the system. This is a common problem with the GM one wire alternators. There is an easy solution. You have to install a diode in the white wire (exciter?) from the alternator. Please don't quote me on this info yet. I'll have to dig out my notes tomorrow and post them.

This happened to me and I couldn't shut it down for nothing. I finally pulled the fuse on the electric fuel pump and let it run out of gas.



In case I can't find my notes, check with Painless Wiring, I know there is something in their manual about this. I got my diode from Radio Shack.





Johnson Rod



Southern California

A one-wire GM alt only has one wire!  That's what you have, right?  The only wire that might have a diode might be for an MSD ignition system.  By the way, what kind of ignition are you running?  Is it points?  If not, you may have to rework your wire from your upgraded ignition system.  There is a slim possibility your key switch may be broken.  When they go, it's usually intermittant.

Remove all the wires from your regulator.  Take the BATT wire off of "B" and connect it to your horn relay (it should be right next to your reg).  That should be the only hot wire used.  One small wire on "A" used to go to the GEN/BATT light, but you disconnected that already.

Hope this helps.  - Dave

Royal Oak, Michigan (Four miles north of Detroit, and 12 miles NORTH of Windsor, Canada).  That's right, we're north of Canada.

Ford 292 Y-Block major overhaul by simplyconnected

Well I may be mistaken but my one wire GM alternator actually has two wires, but only one actually comes off the alternator to the Battery (Red wire). The exciter wire (white one) is connected to the red wire the comes off the alternator. This is the wire that I mentioned that back feeds the system and needs a diode. Don't know, I followed the instructions from Painless wiring and it cured the problem.












Johnson Rod



Southern California

OK, just checked, I guess what I have is a Late Model GM internal regulator Alternator according to my notes and Painless wiring manual. So it has two wies, not one like I stated above. If anyone is using this alternator and your engine doesn't shut off the diode from Radio Shack is Part # 276-1661.





Johnson Rod



Southern California

I have been running a 1 wire alternator, wired directly to the + terminal of the solenoid, for about 8 years.  I had the same problem about 2 years ago.  Started intermittent, but became more frequent.  For me, it was a bad starter solenoid.  Replaced that and all was well.

Ron Grove

Wauconda, IL

To test to see if problem is the solenoid remove the small terminal wire when the car won't shut off.Simple!