Mustang dies when lights are turned on

[garycroix]

Hello all 66 Mustang, 5.0 EFI/AOD. I recently installed a 100 amp one wire alternator in the car since the stock 90s alt I had on it would not be enough to run the electric fan I put on the car. Car starts fine, blip the throttle to get the alt 'turned on,' battery voltage climbing; all is well. Electric fan turns on about 190 degrees, fine. Battery voltage took a hit, but still continued to climb. Great. So I hit the lights, car dies. What do you think? Could I possibly have the timing off? Or the distributor one tooth off?
I'm thinking it may be the dist gear one tooth off, because for a long time the car would not run; the dist was one tooth off. I moved it one tooth over and the car now runs. I set the timing to 10 degrees BTDC, though I really had to turn the distributor module kind of close (relatively, I suppose) to the thermostat housing.
Frustrating....the car is so close to being driven.


Thanks in advance,

Gary in GA

 

[D.Hearne]

Bad grounding. Check all the ground wires. You might need better/newer ones.

 

[JDS68Stang]

Then don't turn the lights on!!!! lol, sorry couldn't resist.

Trace over your wiring, that sounds like your shorting out your distributor to me somewhere when you turn the lights on.
If it just started happening since you swapped alternators chances are your light switch may not be it, but don't rule that out for sure.

I guess one test you could do is pull your #1 plug, ground it with the plug wire attached and have someone turn over your engine WHILE the light switch is on, are you getting a spark?

I'm no expert at this by any means but 100 amps is more than enough
to handle what your running I'd say.

Your one phrase "continues to climb" reffering to your voltage has me wondering whats up especially with a 3G alternator, the fan shouldn't drop it at all, or very little I would think, and then have it "slowly climb back up".

You should get some more helpfull advice by the guys/girls her that are more familiar w/ the 3G problem your having by tomorrow I'd say.

 

[garycroix]

I don't think I mentioned that this isn't a 3G, it is a Summit 100 amp 1 wire alt. By 'continues to climb,' meant that when the fan kicks on, the volts (read across battery) does drop, but starts climbing up again. This is all at 800 rpm/idle.

I have the engine grounded to the frame at four locations, but I'll re-check the connections. Anyone know how to check/test the grounds specifically?

Gary in GA

 

[D.Hearne]

Wiggle the connnections and make sure they're grounding to bare metal and not insulated by the paint.

 

[gjz30075]

Does the car die like you shut the key off or does it just idle too low and quit? If its the latter, then maybe that's why you're suspecting the distributor being off a tooth? Any way you can advance the timing a bit more to see what happens?