'85 XJS V12 with the Lucas alt.

The alt in my car wasn't charging, or at best it was intermittent.
I pulled the alt from my parts car and had it rebuilt at a local
shop with an excellent reputation. He did replace the voltage
reg.

I put the rebuilt alt in today and it charged great - 14.0 at idle
and the lightning bolt was gone! Awesome! I let the car run for
about an hour to charge the batt while I screwed around with my
nonfunctional heat. While doing this I pulled the plug on the
driver's door buzzer located near the passenger's feet (not sure if
this matters).

So I finished screwing with the heat and shut the car off - and the
lightning bolt came on and stayed on.

WTF? This is a known good alt that's working great. Could there
be a short somewhere? Please tell me all I need to do is plug the
door buzzer back in. I REALLY don't feel like pulling this alt
again.

Kirby's book says the charge light staying on is a sure sign the
alt is toast. Ugh...

Bottom line:
Before: Light off/car off. Car on/light on. Intermittent charge (very low)
After: Light on/car off. Light off/car on. Charging great.

Thanks,
D

 

Probably a bad diode in the alternator. Unplug the small (excitor) wire from the alternator and see if the light goes out

Sorry.


Cheers
DD

 

UPDATE:

When my guy rebuilt the alt, he put the noise filter wire back on the wrong prong. So, I then put the exciter wire on the prong where the noise filter should go. Unfortunately I had to pull the alt again to figure this out. All should be well when I put it back in.

Interesting bit of info about how it behaves just by switching terminals.

D