On most modern cars they use electric engine cooling fans so if you add A/C you need to add an additional fan or fans on the condenser to keep your pressures in check. This extra amp load wouldn’t apply to you guys just adding an A/C compressor to your existing combo on a Pig.
I would guess if you see a volt/amp drop when the A/C is running then you didn’t add an idle up solenoid to the carburetor and the alternator is dropping out at the lower idle speeds. If you are running a single wire alternator and idle for long periods or driving at slower speeds with lower engine RPM’s then yes you’ll drain the battery until the alternator is re-energized.
Good luck guys!
