1990mustanggt

I tried a search on this subject, but turned up nothing like it.

This damn thing is about to drive me crazy. I would like to fix this problem before I try to install a 3G upgrade. Here's the problem.

I can crank the car, the amp gauge will show that it's charging. I drive it for more then about 10 mins and it will quit charging. Then after the battery starts to die you can't push the gas pedel without the car spitting and sputtering. Then after the battery is dead the car will die.

Is this maybe that I'm overloading the Alternator? I have two 12 inch fans as pullers that only come on when the car reaches 200 degrees and two 10 inch fans used as pushers that run all the time. I also have MSD ignition. Other then that, I have no other electrical things on it.

My 12 inch fans have relays on them. I thought they were to help keep the circuit from overloading.

windsor306roush

so you have four fans?? hmm...whats the total amp draw?

1990mustanggt

50 amps for this bad boy
http://store.summitracing.com/partde...5&autoview=sku

The other one only pulls about 15 amps. I'm not real sure. It's alot smaller then the Derale.

windsor306roush

ok...thats 65a just for the fans...what size is the stock foxbody alt?
remember, even when you relay the fans...the current is comming directly from the battery, the alt will have to compensate the draw and overwork itself if its too large...swap to a 3g alt and it will deff fix your problems...

do you have a system also?

1990mustanggt

The older alternators only put out 75 amps. The only problem is that that's at high RPM. At normal RPM/idle it only puts out around 35 to 40 amps. I don't know why I didn't think about the over amp problem. I guess it makes sense. I've been wanting to do the 3G conversion, at least now I have a reason to do so.