After switching over from Heat to Cool for the season my Two Stage heat pump goes directly to Stage 2 without even trying stage 1. The outdoor temp was around the upper 40's at the time, which usuallly can be handled by it's Stage 1 setting. It usually at least tries stage one for a certain amount of time.

Here are the simple troubleshooting steps I've tried.

1. Switched it back to Cool and set the thermo low enough to use the A/C....Ran normally, outside fan blade ran as typical.

2. Switched it back to Heat, but when I raised the thermo setting to start the heating cycle, instead of seeing the temp setting increase as I pressed the button it just indicated OFF.

3. I switched the dial to the Change Heat Settings and cycled through the programable settings for the day. Then after switching back to it's Run cycle I was able to reset the Heat setting low enough to get it to turn on, but it went straight to Stage 2 heat.

I'm suspecting the thermostat is bad but I'm open to other theories or tests.


It's a Lux TX9100E, just about 6 years old. No problerms at all until now.