64 Barracuda Alternator Question

[djf5502]

I ordered and received a replacement alternator for my barracuda. The old one was original and it finally died. I have made no wiring changes to the car, it's all original. The new alternator is 60 amps and has two field terminals. I understand that I need to ground one of the field terminals on the new alternator to make it work. My question is by grounding one of the fields, is my charging system now getting 60 amps or is it getting 30? I believe by grounding one of the fields, the alternator is basically equivalent to the old one right?

 

[pettybludart]

Yes.Just ground the 2nd field.

 

[BillGrissom]

My question is by grounding one of the fields, is my charging system now getting 60 amps or is it getting 30? I believe by grounding one of the fields, the alternator is basically equivalent to the old one right?

Yes, equivalent except the max output can be 60 A instead of 30 A. That is with a full 12 V applied across the field terminals by the Vreg. Even then, you wouldn't get 60 A output at idle.

There is concern with 60 A output being too much for your wiring and ammeter. I think your ammeter is 50 A max, so 60 A probably wouldn't damage it. More concern is at the bulkhead connector, which often melt even when factory original (corrosion generates heat). Too bad you don't have a 63 or 65 which have special "buss bars" for the high-current ALT and BATT wires. Indeed, I am putting a 65 bulkhead in my 64. That requires cutting the square hole 1/8" taller. Even then, all connections must be clean. I also use silicone grease.

Several ways to limit or mitigate high current. Many run a thick wire from ALT out to BATT+. The starter relay stud is a convenient place. That is the MAD Bypass. To keep my ammeter functional, I put a diode pair in series, so that path flows only as needed (keeps ammeter dV < 0.75 V). Read my post, but not for electrical wimps. Another method (I just thought of) is to put one or more diodes in series with the alternator field. That would drop ~0.75 V each (Si diodes) to limit max dV across the field and thus alternator output (to ~30A your car was designed for). You would need to design for the power dissipation, but the field current is fairly small (~1 A?), so small diodes should work.

 

[375inStroke]

If you don't have anything that's going to draw that much current, you have no problem. I think you may have lower voltage at idle, though, since there are fewer windings of heavier gauge wire in the coils.

 

[djf5502]

Thanks for the information. I did the get the new alternator to work, but after reconsidering I had the old alternator rebuilt and reinstalled it. I decided keeping it as original as possible would be best.