My heat pump heats just fine, and the air handler is working, but it won't do the A/C in summer. I had this problem with another hp and it turned out to be the thermostat. Are there other things I should consider before replacing the thermostat? Ducts are being cleaned.

You have a problem that has resulted in the reversing valve not working. This could be a number of things, even incorrect wiring of the t-stat. You need a technician to fix this, you cannot unless you understand heat pumps. They are really simple to a tech, but you will waste a lot of time and money trying to replace parts when there is another problem. If you were in Jacksonville I could help. DrTom4444