Cooling/Orange Wire issue

[doberman]

I've had this particular Nest since about 2017.  I recently tried to use cooling via the Nest thermostat.  The room got hotter.  Had a tech come today to check the system.   Said everything in the heat pump system is working fine, voltage correct, etc.  But when swapped the Nest with a standard thermostat, the system cooled perfectly.  He then determined that the Nest is "not energizing the O terminal in cooling mode."   I tried restarting the Nest, and no change.  Please advise.   Thanks.  

[Markjosephp]

Hello doberman,

Thank you for sharing your experience with your Nest Thermostat. I appreciate your proactive approach to troubleshooting the problem, including having a technician inspect the system. It's good to hear that the heat pump system itself appears to be in proper working order and that the voltage levels are correct.

Have you had a chance to change your system's orientation in its settings? Here's the troubleshooting heat pump issue article. 

Let me know how it goes.

Best regards,
Mark

[doberman]

Thanks, Mark.  That did not fix it.  I ended up calling Nest and speaking with a tech.  He had me switch every wire in various combinations, and nothing fixed it.  In fact, by the time he was done with his suggestions, I had no heat either, which was disappointing, so it became an urgent problem.  His guess was that the backing plate was bad, which seemed a bit unlikely to me.  He said he couldn't guarantee that if I could find a replacement backing plate, that it would solve the problem, so he recommend an entirely new Learning Thermostat.  With no heat, I opted to do that, and the system does work.  So it appears that either the backing plate of the unit itself failed -- which was disappointing.  Anyway, thank you for your suggestion.