help! my batteries keep dieing!!!!!!

[xtreme2own]

hey guys! first post here. looking for a few answers,

I have a 1990 Mustang GT 5.0 and i purchased last week. When i bought it the guy had a brand new in box alternator for it, and said that, that was the reason the check engine light would illuminate about 30 minutes after normal driving. I took it to a shop (before purchase) and they said that the trouble codes were not listed in the computers memory. So, i bought the car, thinking it would be an easy fix.

I bolted in the new alternator. Put in a new optima battery (800CCA, 1000 CA). After four days, the battery amps on dash kept getting lower and lower, until today, when it actually would not start. My question is, what could this be? Where should I start? What should I look for...

Some things that have changed in the past few days:

Ive installed, pullys, including alternator pullys. I dont believe that this would lower the charging ability to where it kills the battery however. Especially when im not running a big stereo system.... yet..

New alternator. There are three wires to attach. You must cut out the harness and hard wire it, per aftermarket alt. instructions. There are three wires, a small white one, and two bigger black ones with orange stripes. I got the white wire right, but when connecting the two black ones i MAY have mixed them up? Instructions said just to connect them.... giving me the impression it did not matter.

The refurb alternator i purchased may be bad? Lifetime warranty so i doubt it.

These are the things ive changed. Also, the car had a rigged electric fan that is wired funny and needs to be cleaned up a bit. I plan on taking it to a shop but maybe you guys would know where to start touble shooting this issue? Or give me some ideas of what may have gone wrong?

Let me know, thanks in advance for all the help!!

 

[88mouse]

I believe you may have a wire crossed somewhere. Im not a big fan off cuting the wiring harness. But most people hear upgrade to the 3g alternator. There is a write up on the swap in the sticky. But I would go back and double check the wiring.

 

[HISSIN50]

You dont have to cut any wires to do the bigger alternator.

In the way you did your wiring (which we don't recommend - more later), you would connect both of those blk/or wires together, and put them on the alternator's big charge stud (that has a nut).

The regulator plug is the same for both 2 and 3G's so you just plug it in.

We recommend not using the stock charge wires because they are a fire hazard. See the sticky in the Useful technical thread index for how to do it safely.

As your system stands now:
On your regulator, check the A terminal. It should show the same voltage as the charge stud on the back of the alternator.

Reman'd alternators (and all electrical parts) suck. I have them all repeatedly bench tested before buying one (I have had them test bad right out of the box). Don't overlook that this is your issue.

If you desire to rewire your fan circuit from scratch (my recommendation), post up and we can help.

Random thoughts.
Good luck.