So I've just completed my 305 to 350 swap in my 91 firebird. I kept the tbi system in place for the swap. Ive been able to get the car started but the alternator isnt charging the battery. I've used two different batteries (one new, one from my DD), two different alternators (one new, one that tested good and worked before swap) and it hasn't fixed the issue, so it must be in the wiring. The problem is, my wiring on the starter doesn't seem to match any wiring diagram or info I've found previously and I'm confused as to what's what.

I have 3 connections on the large terminal. One is for the battery. That one I have identified but the other two I don't know what they are or where they go. The first is an orange fusible link to another orange wire. The second has 2 fusible links tied into one eyelet. Both are orange on the starter side. The other side of one has a larger red wire and a smaller red wire. On the other is a single red wire the same size as the fusible link.

On the small terminal is a purple wire and another orange fusible link with a larger red wire on the other end of the fusible link.

Which one of these many wires goes to the alternator and how do I test for a bad fusible link? Keep in mind I haven't messed with any of the wiring down on the starter and everything worked fine before the swap.

 

just run a 10 gauge wire from charge point on alternator to positive battery cable on my 90 that is how it was from factory. But first use voltage gauge and see what the alternator output is.

 

The purple wire on the starter is the starter exciter which activates the solenoid only during the start sequence. Rest of the large wires minus the main battery feed wire should all have fuseable links. I think there are 3 of those. You can voltage test each of those beyond the fuseable link to ensure they have 12+ volts.
If you test the singe (+) wire on the ALT, you should get around 12 volts providing the battery is fully charged. To my knowledge most GM alternators use the Check Engine or SES light in place to act as a 333k ohm resistor to let the ALT go into low or high charge.
A backyard mechanic's test would be to ensure the battery has been load tested and fully charged. Start the car and disconnect the negative terminal on the battery. If the car stays running, turn on your lights, heater, defrost etc to put a load on the ALT.. Your Alt should be able to handle everything all alone and just uses the battery for storage and starting only. If the car dies immediately, Generally, that means the ALT is bad or you have bad wiring which requires more research and tracing wires. A bad alternator will kill a battery. Let me know if this helps

 

All the wires have fusible links. There are 2 other connections on the large terminal and 1 on the smaller terminal. Like I said before, I haven't touched the wiring so it's been like this ever since I've owned the car and it worked before. All of the fusible links are the same size. They all say 10mm fusible link on the wire. Any ideas as to what the other three go to?


I have 12 volts at all times to the 10 ga. wire on the back of the alternator and the red wire in the 2-wire connector. I don't know what I've got with the car running because I can't keep it running long enough to check. I also have 12V to the brown wire with ignition in run like I"m supposed to.

 

A quick ******* test to see if it is charging is to see if a screwdriver (something metal) sticks magnetically to the rear shaft of the alternator. This means there is an electromagnetic charge which means the alternator is charging. It will not tell you how much it is charging but a good test in the middle of no-where with little to no tools.

 

I know it's been awhile but Ive been crazy busy with school. I finally solved my problem. It turns out I had a wire in the wrong location. When putting the motor in and hooking up wires, I made an assumption which turned out to be wrong. The 10 gauge wire on the back of the alternator has a single fusible link on it which i thought went to the starter. Since it had a small eyelet on it, it could only go on one post (the small one). This past weekend, I decided to pull that wire off and check continuity and it was fine. Since the alternator, battery, and now the wire checked out, the only possible solution was that it was in the wrong spot. I began looking and the only other place it could go was a spot in between the battery and radiator where there is a small stud with a battery lead coming straight off the positive terminal. I hooked it up and cranked the car and I had 14 volts for the first time.