mgmuscari

Tonight my alternator blew for the third time in three months... First it shut off completely, and after fiddling with the wiring harness for a bit, when I started the car it started arcing from the coils to the casing. This is a 3G alternator in a 1989 Mustang GT. I've examined the wiring diagram closely and it seems to me that it could be something wrong with the yellow sensing wire. Tomorrow I'm planning to do the following:


Replace alternator
Replace battery (possibly bad cell zapping alternators?)
Run yellow sense wire from connector to positive charge terminal on alternator
Run white stator wire from connector to blade connector on alternator
Disconnect/remove existing black/orange charge cable and yellow sense wire from harness
- Possibly run new red/green engine on wire from alternator connector to starter solenoid/ignition switch source
- Possibly run a ground cable from alternator body to chassis

Basically i'll be replacing the whole charge system here, because I'm pretty fed up at this point. The charge voltage with this alternator has remained rock steady at 14.7 volts since I installed it, with the exception of one intermittent event a few weeks ago where the same arcing problem occurred. Now it won't go away - here are my questions:

- Could a faulty sense wire have caused the regulator to fail completely?
- Would running an extra ground cable help in any way? AFAIK it grounds to body through the alternator mounting bracket.
- If this doesn't resolve the problem (and I blow another alternator), where should I start looking for the root cause? Failure modes have been as follows:

- Seized alternator caused pulley to shatter (Motorcraft 3g 90A)
- Alternator began to seize, replaced before failure (Summit Racing 1-wire 120A)
- Alternator arcing internally from field coils to case, no output

PRO50SC

Where are you getting the units from?