I've vacuumed the system down to around 20" and left for 30 mins with almost zero loss. Still, when I try to add refrigerant, the low pressure on the gauge jumps to nearly 110psi and it'll take no refrigerant. When I force the compressor to engage, the low side pressure jumps to around 120psi and the high side goes to maybe 25psi. Still, it takes no refrigerant.

I've charged a few of these things and I've NEVER seen the low pressure that high when charging or running. Usually it's in the 45psi range when the compressor is on. Way below that and rising while refrigerant is entering the system.

I'm thinking something mechanically is wrong with the system. Anyone have any ideas?

Looks like no A/C for Carlisle this weekend...