Join Date: Aug 2006
Location: Arlington, VA
Thanked 14 Times in 12 Posts
Rep Power: 12
If you're only getting 12V at the AB, then either your wiring is too small or you have some bad connections (loose or corroded terminals, loose or corroded nuts or screws, etc.).
Try that first.
Inrush current can be much higher than the run current, even if the compressor is working properly. Normally, it's only for an instant or two before the compressor gets rolling, whence the amperage draw will drop to about 3-6, depending on the compressor.
If your compressor starts when the engine is running, that's a sure sign that there's a bad wiring connection somewhere.