Battery voltage prob

[sandman0023]

I have an 89 GT. My mods include: 120 powermaster alt, kenwood amp, subs as well as new speakers and stereo, aftermarket pullies. My voltage is low (in the red) when I start the car up. After about 10 min the voltage is normal. I replaced my battery with an Optima and still have the same problem. But now it has to be about 1000 rpms to stay at a normal level. What would cause the volts to be so low? Could it be the Ford Racing pulley on the alternator (it was fine before I replaced it)?

Other mods:
BBK Cold-Air intake
Flowmaster American Thunder Exhaust

Future Mods:
BBK intake manifold & 75mm TB
C&L 76mm Mass air meter 19lb
19lb injectors

 

[HISSIN50]

did you do the wiring upgrade when you did the alt? did the problem just arise with the new pulley? is it underdriven?

have you checked the alt cable for voltage drop? all motor grounds up to snuff (including upgraded/enhanced grounds for the alt)?

good luck.