Most often a reversing valve stuck in cooling mode, a refrigerant charge problem, or a failed defrost cycle. It is rarely the thermostat, though that is where people usually start. All three are diagnosable in one visit.

Most repairs land between $180 and $650 depending on the part. Capacitors and contactors sit at the bottom of that range, fan motors and reversing valve work at the top. You approve a flat price before anything starts.

Most visits run 60 to 90 minutes including the diagnosis, because the parts that commonly fail are already on the truck. Compressor work is the exception and usually needs a return visit.

There is a diagnostic fee and it comes off the bill when you approve the repair. If you decide not to go ahead, you pay the diagnostic and nothing else.

Yes. After hours you reach the owner rather than an answering service, and if it can wait until morning he will tell you that rather than charge you a call-out.

All of them. Carrier, Trane, Lennox, Goodman, Rheem, American Standard, Bryant, York and the rest. Heat pumps share the same failure points regardless of the badge.