DJ19895.0

I just bought a 1988 mustang gt, and when you have the head lights and fog lights on and the heat on hi, the voltage drops to where it is using a little power form the battery. (I tested it with a voltmeter) When you bring the rpm's up to about 1500 or above it resumes charging. Is this normal, is my alternator going bad, or could i possibly have underdrive pulleys? What would the diameter of the alt pulley be if it was an underdrive? This is not a big problem because even after night driving, it starts fine and the battery remains charged. Just thought i'd ask and be on the safe side.

marx91

whats the volts at idle? head lights are a big draw on your battery anyway
and it is possible you have u/d pulleys, i went to a 130 amp alt.
b/c of my electric fan and under drive pulleys, stock alt. is 75 amps

SmokumsTheBear

Off topic, but Marx, where could I buy a higher amp alternator? Mine got wet today from going through a puddle. Now I have a number of issues.

marx91

the one i have came from pep boys, its for a '94 gt

SmokumsTheBear

Ah, sweet. Ill have to swing by there tomorrow. Thanks. I also have this Lightweight aluminum pulley for the alternator. Would it be wise to use that with a new alt?

marx91

yeah, but you'll have to cut the big plug off, it has 2 black 10 ga. wires w/ orange stripes
and a white wire w/ a black stripe, then get a ring lug and double crimp the 2 black
wires together and put a spade connector on the white wire and it plugs into the top
of the alt. thats your voltage reading.

*edit* i got a long battery cable and ran it from the alt. over to the solenoid as well

silver91gt

I got rid of those small stock wires and just used some 4 gauge wire to the solenoid.