charging

[air-cooled or diesel]

so i have an old generic alternator thats charging @about 13.7-13.8v, when i have the lights on its a healthy 13.4+v, but when i have the a/c and lights on its about 12.7v, sounds like the bottom. then again its about 15yrs old, im planning on getting a napa bosch alt, prob ok as far as being a bosch. i want to see my #s then. i dont see how many volts the a/c uses, unless most goes in to the rad fan.

[82vdub]

This is likely normal. If you keep adding load to a system, the voltage typically will drop a bit. If you ever notice when you flick your AC on at night and the lights dim, it's because of the voltage drop.

[air-cooled or diesel]

i had, back in the 80s and 90s a couple of t/1's that had generators or swap-overs from gen to alt. so i know about voltage drop. none of those cars had a/c, that seems a lot of voltage drop for an a/c, and 12.7 would seem the minimum charge, i ll see when i get a new alt. i do believe the change up to alternators was for more steady current flow, as a generator lights would dim for low revs and more lights, accessories. an alt has much less change like dimming lights for more circuits turned on and stuff.

[vwtyp133]

The voltage drop with A/C use is common. What I've heard is that the A/C compressor clutch draws a fairly heavy load, plus most folks generally kick the HVAC system fan speed to "High" when they switch on the A/C. Result: significantly more current drain, resulting in lower volts. IDK... Could be just evil rumors(?).

[air-cooled or diesel]

i just got done with putting back together an a/c system, the 2 wires going to compressor, for the clutch, arent very big, and the one has to be ground, so where is all this current going for the clutch? i was under the impression the clutch took a good amount of current, i mean you have clutch, rad fan, vent fan, and a few sensors, a fair amount of charge to run this. i want to see my charging #s after i get new alt. not bad for an old generic alt, the voltage regulator says spain on it.