[color=#383a3b]Florida home has a heat pump split system. Condenser is an [/color][b]Ameristar M4hp4042a1000aa[/b][color=#383a3b]. Air Handler is an [/color][b]Ameristar M4AH4044A1000aa[/b][color=#383a3b]. The fan and cooling in our current heat pump thermostat work but when the heating option is on, the fan works but the home does not heat up at all (even after many hours). This is how the thermostat is set up (picture included).[/color] [b]Old Thermostat (Honeywell Thermostat 50018270-002 - no batteries used):[/b] [img]https://www.diychatroom.com/cdn-cgi/image/format=auto,onerror=redirect,width=1920,height=1920,fit=scale-down/https://www.diychatroom.com/attachments/img_2344-jpg.638905/[/img] [color=#383a3b]Switching the position of orange to O did not fix this. Moving the white wire to E also did not work. As a test, we switched our old thermostat with a new smart thermostat ([/color][b]Honeywell rth6360d1002-1738[/b][color=#383a3b]) and somehow the heating now worked[/color][b] BUT[/b][color=#383a3b] the cooling stopped working. The home raised in temperature within minutes. The wirings were all the same in this new thermostat EXCEPT B/O was one connection on the back panel, and the white wire ONLY worked when it was placed on W, not W2/Aux or E. There is no defrosting situation here with the outdoor condenser.[/color] [img]https://www.diychatroom.com/cdn-cgi/image/format=auto,onerror=redirect,width=1920,height=1920,fit=scale-down/https://www.diychatroom.com/attachments/img_2641-jpg.638909/[/img] [color=#383a3b]We reconnected the old thermostat and the situation there is the same, but when we reconnected the new thermostat to get some heat again, it stopped working altogether. Right now the old thermostat is set up and I'm having trouble figuring out how to get the heating to work. It's clear that the cooling and heating functions of the heat pump are fine. I have no idea how to troubleshoot this and would appreciate some help to avoid freezing at our place. I included photos of the wiring in the outside condenser for reference. I can't find a manual for my exact model but it seems based on other manuals for Ameristar condensers that it utilizes B for the reversing valve.[/color] [color=#383a3b]Thank you in advance.[/color] [img]https://cimg4.ibsrv.net/gimg/www.doityourselft.com-vbulletin/2000x1504/img_2632_33d5f2e62acee772c95843bef1d374c1b31e9ea6.jpg[/img] [img]https://cimg1.ibsrv.net/gimg/www.doityourselft.com-vbulletin/2000x1504/img_2630_5092754bfd1f8861208e2d1f6337bc91140e802e.jpg[/img] [img]https://cimg0.ibsrv.net/gimg/www.doityourselft.com-vbulletin/2000x1504/img_2625_f33faf94ddc746b550cc3e569f6f023414f86b10.jpg[/img]

I have a new Trane heat pump that was installed in Sept. I live in Charles Town, WV. System has propane gas furnace for backup heat. System does not seem like it has been operating correctly since installed. Tech has been out here 3 times now trying to figure out what is going on. Problem has been that when unit goes into defrost it is dumping a lot of cold are into the house and temp will drop 5-7 degrees before it recovers which sometimes can take up to an hour. Anyway, my question for now is about defrost. When the tech was out here the other day he was explaining what happens to the unit when it goes into defrost. When I asked him what actually tell the unit to go into defrost, I understood him to say that it was a temp. sensor and usually would go into defrost when temp goes below about 40. Is this correct? The reason that I am asking is that when I got up this morning the inside temp was 69 and the outside temp was 56. Not long after I got up the outdoor unit fan when off, so I guess it went into defrost and the backup heat came on. Again the indoor temp went down 4 to 65 within 10 minutes. With the outdoor temp at 56 why would the heat pump go into defrost and the system have to run back up heat? Seems like a heat pump should be able to do the heating when the outdoor temp is that warm. Thoughts on this? Thanks