I just got the after market Old Air a/c up and running in my '69. Now the altenator quit charging. It was a remanufactured Ultima 78 amp single wire (car had been changer from external to internal voltage reg) unit from O'Rielly's about 6 months ago. I have since read bad reviews about these and other remanufactured altenators. But my question is do I need more than 80 amps with the new a/c unit and where can I get a dependable unit?

 

With AC 80 Amps could be marginal, especially if you also have a high power sound system, but regardless of load the alternator should not die, however the voltage may drop as the load increases. If the alternator is overloaded a fuse or fusible link may blow to prevent the wiring from going on fire. If you want to know how many amps you need, add up the total amps of each item drawing power and add 15-20 % to take care of surges.

 

I would buy the biggest alternator you can get.

 

DB Electrical, go for a three-wire unit.

 

I'm going with Thor on this one.

I'd think you'd want something above 100amps to make sure everyhting gets the proper power.

 

The wiring in this "old barn find" isn't in the greatest of shape (spliced, taped. and missing). Do I really need over 100 amps if not adding elaborate sound system and lights? The only thing added is the a/c system and electric fan. Also why put 3 wire back in rather than 1 wire?

 

First it might be to your advantage to get a new engine harness for your car if it's in that bad of shape, right there can be a problem.

As for the amps, if your just doing a stock type rebuild, an 80amp should do the job.

On my race car, I run a 105amp to make sure all the electronic stuff gets the proper power supply.

And last, as for 3 wire vs 1 wire, read this info, it might be helpful:
Catalog

 

One wire, 4/0 gauge cable needed...LOL
C630 - 14V 350 Amp