New ignition switch----Old problem
Thread Starter
Racer
Joined: Sep 2011
Posts: 414
Likes: 55
From: Humboldt county Ca
New ignition switch----Old problem
Took the column out of the '75 this afternoon and replaced the ignition switch using Jim Shea's excellent instructions.
Put everything back together and the same old "Run-on with the ignition off" problem is still there. When I turn the key off the engine sounds like it cuts down to 6 cylinders. turn the key back to on and goes back to normal idle. Seems also to be more prevalent when the car has warmed up regardless of whether it's been driven to warm or just idled to warm.
Anybody got an idea????
Thanks,
Stump
Put everything back together and the same old "Run-on with the ignition off" problem is still there. When I turn the key off the engine sounds like it cuts down to 6 cylinders. turn the key back to on and goes back to normal idle. Seems also to be more prevalent when the car has warmed up regardless of whether it's been driven to warm or just idled to warm.
Anybody got an idea????
Thanks,
Stump
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,851
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
The pink wire that controls the distributor power runs from the distributor straight to the ignition switch.
It also splits off.. goes the to the fuse panel (gauges) and off to the fuel gauge, the temp gauge, oil pressure gauge, the tach, parking brake indicator lamp,
I’ll assume you adjusted the switch and didn’t use the “old” position as a mark for where to bolt the new one down. (Some people make this mistake). If you did adjust it then great, if not you should.
If the switch is cutting off the power at the switch connection, then I would go to the distributor and see if you have power there.
Something else may be back feeding voltage on this wire to the distributor. Without starting the car I would first test with a probe to see if the switch is working correctly. (I have a test probe that I filed the points down to needle like size. This allows me to pierce the plastic with ease and it only makes a tiny hole). Then I’d probably un-plug the switch and see if there is voltage on the distributor wire with the key off.
It also splits off.. goes the to the fuse panel (gauges) and off to the fuel gauge, the temp gauge, oil pressure gauge, the tach, parking brake indicator lamp,
I’ll assume you adjusted the switch and didn’t use the “old” position as a mark for where to bolt the new one down. (Some people make this mistake). If you did adjust it then great, if not you should.
If the switch is cutting off the power at the switch connection, then I would go to the distributor and see if you have power there.
Something else may be back feeding voltage on this wire to the distributor. Without starting the car I would first test with a probe to see if the switch is working correctly. (I have a test probe that I filed the points down to needle like size. This allows me to pierce the plastic with ease and it only makes a tiny hole). Then I’d probably un-plug the switch and see if there is voltage on the distributor wire with the key off.
Last edited by Willcox Corvette; Jun 8, 2013 at 09:08 AM.
Le Mans Master
Joined: Dec 2007
Posts: 6,422
Likes: 591
From: McHenry Illinois
Also try unplugging the alternator wire then see if it acts the same, I have seen one where the two wires on the alternator were reversed and the alternator would back feed the ignition and not let it turn off.
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,851
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Thread Starter
Racer
Joined: Sep 2011
Posts: 414
Likes: 55
From: Humboldt county Ca
Ugh! Now that I think of it----uh----I replaced the alternator a couple of weeks ago and the problem strated right after that. Maybe my "Hecho in Mexico" rebuilt alternator has a bad diode or some wires crossed. Should have waited the week for a new one but summers here are short and driving the car is more fun than working on it. Next time I get it to do it's trick I'll pull the alt wires and see what happens.
Thanks!
Stump
Thanks!
Stump
Thread Starter
Racer
Joined: Sep 2011
Posts: 414
Likes: 55
From: Humboldt county Ca
'75, good suggestion! Pullng the alternator wire cures the problem. Since the two wires are molded into a single plug and that can only go in one way I'm thinking any wires reversed are within the alternator case itself. Since this is a heat related problem, my theory is that the alt has a bad diode and heat causes it to fail. I'm taking this rebuilt thing back Tuesday and replacing it with a new (not rebuilt) unit.
Well, at least I'm not afraid of tearing out the steering column anymore and I've got a new ign switch and rag joint!
Thanks to all.
Stump
Well, at least I'm not afraid of tearing out the steering column anymore and I've got a new ign switch and rag joint!
Thanks to all.
Stump
