Engine Missing, Alternator Light on with key off

kpfoten · 10-09-2003, 07:52 PM

The hits just keep on coming...

I've had a miss at about 3500rpms ever since I put everything back together in my '77 2.7. I had the alternator rebuilt, blah blah blah...

Well, the miss got worse today, the tach was jumpy on the highway, and to kick me in the teeth, the alternator light stayed on with the ignition OFF!

The wire that hooks to the Pertronix ground to the dizzy looks horrible (Ie bare wires, cracks, etc). I think this also goes to the alternator? (It branches?)

Anyway, any help would be appreciated. I'm tired.

Thanks!

Doug Zielke · 10-09-2003, 08:09 PM

Quote:

Originally posted by kpfoten
....... the alternator light stayed on with the ignition OFF!

Shorted diode(s).

kpfoten · 08:19 PM

Could it be a bad DF wire? Light is off when ignition is in the on position, but when running it is off as well...

More importantly, I think the issue that was affecting my jumping tach/missing is also tied in with my alternator somehow... (Ie. wiring)

Could this be?

fintstone · fintstone's Garage

I agree with Doug on shorted diode(s) in voltage regulator...that will also cause fluctuating gauges because shorted diode allows alternating current (AC) signal from alternator into direct current (DC) system.

kpfoten · 10-10-2003, 06:14 AM

Thanks for the replies. Back to my question about the bad DF wire, would a bad ground short out the diodes? I was looking at that wire last night (again) and noticed how many cracks were in the insulation and how much exposed wire is present.

john walker's workshop · 10-10-2003, 06:52 AM

diode problem in the alternator. rebuild or replace. i doubt the wire shorted or it would be toast.

fintstone · fintstone's Garage

A bad ground will not short out anything. Only when a wire with voltage on it is grounded is there a problem of excessive current causing short. (still fix the wire if it is poor damaged). Sometimes (rarely) a really, really bad battery will also have similar symptoms to yours..dead cell pulls so much current that the idiot light circuit/diode see the voltage as in the wrong direction.

kpfoten · 10-10-2003, 08:01 AM

Thanks for the info.. I've got a new battery, etc. I'm a little bummed because I just had the Alternator rebuilt in Albuquerque, but I don't think the guy re-did the diodes--he said the soldering was just cracked, so he resoldered and put in new bearings...

I'm just trying to figure out if it was anything I did wrong. I did notice when I first installed the alternator that the light was on briefly with key off, then it was off for a few months. Now it's on. Arrgh...

About the only other thing I did was install a battery cut-off switch, ground the Pertronix to where the points were grounded (which is the same wire leading to the alternator--DF?).

bigchillcar · bigchillcar's Garage

Kris,
Sorry to hear about the problem. I doubt it's these things, but I thought I'd post other things that have caused sysmptoms of a jumping tach: points that are closing (old) and bad coil wire.
Ryan

kpfoten · 10-10-2003, 08:47 AM

Thanks Ryan. I've got Magnacore wires on, and that coil wire _does_ seem to be not seating all the way... Maybe i have to get it to fit better..

echrisconnor · echrisconnor's Garage

If your engine is missing you might put up posters around the neighborhood describing what it looked like. Maybe offer a reward.

kpfoten · 10-10-2003, 09:06 AM

Right... I live on the Rez.. I'm sure it won't be showing up anytime soon, but I _could_ check the pawn shops...

bigchillcar · bigchillcar's Garage

Kris,
I've got the Magnecores as well. How old are your points? You start getting backfires as well when they start to close. In a pinch, you can clean them with a dollar bill...uh, I mean you need to use a $100 bill of course...

Ryan

kpfoten · 10-10-2003, 10:16 AM

HAH! I actually have a Pertronix electronic ignition installed. No backfire noted, just the engine missing.

kpfoten · 10-14-2003, 09:31 AM

Update--I went out to my garage, flipped the battery switch--no alternator light on (with the key in the off-position). Turned the key to on, alt light is on. Started it up, alternator light off. Everything seems normal. It's charging normally, etc.

I'm not sure what's going on. Electrical gremlins, I imagine...

Jdub · 10-14-2003, 09:55 AM

Here's a strange story -- I was helping my father with his Saab Turbo 99. He had caused a spark between the alternator's wire connection post and a ground. The Alt light had come on as a result.

I told him I'd come over with a multimeter and we'd check the voltage output. He decided to charge the battery beforehand and took my advice to pull the battery and not try to charge it in situ.

We hooked up everything and the Alt light was still on. Beyond this, the wipers, horn, rear defrost, oil temp, gas gauge did not work.

I told him to just take the car for a spin. This had worked for me when my rebuilt alternator, prior to driving, had not caused my Alt. light to go out.

Sure enuf, he takes it for a drive and everything snaps back into line!

There has to be some inherent resistance that needs to be "overcome" in order for things to work?

John

kpfoten · 10-27-2003, 04:43 PM

Fixed it! The ground wire I connected to my Pertronix ground had some cracked insulation, exposing live wire. Replaced the wire--no more missing, no more bouncing tach. You should've seen the smile on my face when I was driving it!