My 2015 TXL Tech PKG 3.5 is having a weird AC issue... It started when the blower motor would speed up and slow down with the engine RPMs significantly... . Then, when not on the accelerator, the fan would slow down SO much, it almost seemed like it stopped. Then, intermittently. it would stop blowing cold air at all. I had the blower motor and resistor (I think that is whet the called it) replaced and the problem returned. The system is a little low on referigerant but not much. Any ideas what would cause such a problem? It seems to be getting worse.

Thanks