A/C will switch from max A/C to just the regular speed

Hello,

This sounds like the controller is bad causing the problem you have described. Here is a wiring diagram for the system so you can see how it works and the panel removal instructions. You can see the compass is tied to the HVAC system. I would try a used unit to see what happens use may need to get it initialized.

Check out the diagrams (below). Please run some tests and get back to us.

Cheers, Ken

When you install an electrical component sometimes it must be initialized much like when you add a computer component, same thing. Most shop can do it for about $130.00.