I have installed a Goodman heat pump and a Honeywell RTH5160D thermostat. I chose that thermostat because it is supposed to switch automatically between cooling and heat modes. The system has been working fine all summer for cooling. But, I cannot get the system to switch to heat mode. I made sure the reversing valve wire is set for the O circuit. Goodman heat pumps use the O circuit. How I suspect the problem may be in the wiring where the heat pump, air handler and thermostat are wired together.
Edit (11/20/2019) Sorry for the delay in getting back. Thanks for your help! Model number for the Goodman is GSH130181 (1.5 ton). Here's a link to the manual and wiring diagram: Goodman GSH130181 Installation Manual. System operation is described on page 25 of the manual. That may help.
The hp is currently running with the 19 year old Ruud air handler. I haven't yet gone through the torturous process of putting the Goodman air handler in the attic crawl space. But, my impression is that the wiring is pretty standard.
One issue could be that Ruud used the B circuit and Goodman uses the O circuit for the reversing valve. The thermostat is set for O, but it's a Ruud air handler. I don't know what the implications of that are.
I'm wondering if the problem might be that the reversing valve is stuck on the Goodman. It was about 3 years old when I got it, and sat in storage for 10 years. If I can located the reversing valve, I'm going to try frapping on it with the handle of a crescent wrench and hope to jar it loose.