OK, this has become a problem again for me now that I fixed the A/C (was a bad connection at the high pressure switch on the compressor).

When idling with the air on max a/c and the blower on high - volts indicated on the meter drop way low, 10-11V. If I rev the motor the volts come back.

So whats the normal current draw for the A/C compressor clutch? And for the blower motor on high? I know the cooling fan runs non stop when A/C is on, so whats the current draw for that?

Problem doesn't happen nearly as bad on Norm or Bi-lev, or with the heater or even defroster.

It's worse with the lights on - this tells me something is either pulling about 20 amps, or possibly its time for a new battery and hi output alternator.

Whats the difference electrically between max and norm (or bi-lev) A/C? From what I can tell it only makes the blower push more air - or is there more to it?

 

There is no difference in current draw between normal A/C and Max A/C. The only difference is that on Max A/C it is recirculating air from inside the cabin instead of drawing it from the outisde (a vacuum-operated servo opens a flapper on the HVAC manifold to shut off air from the outside and start drawing it from inside the cabin, underneath the dash). Sounds louder because you can hear the blower fan sucking the air from inside the car on Max A/C, where on normal A/C the sucking noise is outside the cabin, from the cowl area near the base of the windshield.

 

I'd tend to think that if any of these devices were drawing excess current, they'd likely cause a fuse or fusible link to blow.

My car could use a beefier alternator as well. I use a DC to AC inverter to power my laptop for datalogging. At night with the heater on, system voltage goes low enough that the darn thing shuts off at idle speed. I have to turn the heater off so it won't turn off.

I think the factory alternator is only like 80 amps output at engine speeds higher than idle.

 

I wonder if perhaps I have a blockage in the duct leading from the cabin to the blower? It definitely only gets bad on max a/c.