Replace the nEsT then have a tech diagnosis and repair.

 

So you had a tech come out and say it needs a board
Do you bypass the attack in order the board yourself online
Installed it and it doesn’t work
I would call the Tech back

 

thanks for the follow ups.

BNME8EZ - do you simply recommend removing all nest thermostats? or do you think it is causing an issue?

pecmsg - before any issues - the board was making a loud and constant buzzing.

The tech came and recommended the buzzing board could be an issue (the status light was solid with out codes at this time), but it was working at the time he left and all was well: the board continued to buzz, but was blowing cold and seemed to be running correctly and the tech left.

Following that, the unit would simply run cold air and continued to cool down the part of the house past the t stat settings. I have had misdiagnosed issued before, and decided to swap the good units board with the buzzing board. That solved the problem, but I still only had one board that was working correctly. It seems straightforward to order new and replace, but.... now I have code 25.

I assume there is some sort of set up / programming step that needs to be done, or the board I ordered is not compatible with my system despite Carrier's guides, or defective.

 

I suggest you get a different contractor.

 

Unfortunately, this site does not provide diy assistance.

Either call the tech out to setup, the board, or sell you the correct board if the one you have is not correct, or search for a diy forum.

Sorry.

 

thanks.

 

Humming usually means Low Voltage in or out. Your alleged tech didn’t measure anything anywhere.
Swaping the boards is not troubleshooting, you could have had a bad connection weak or loose.
You need a contractor on site with training and the tools needed.

 

nSet thermostats are known to cause false error codes and/or problems in equipment that changing a part doesn’t fix but change to a different stat and the problem leaves.

If I understood you changed a board and the problem stayed. So you either had bad diagnostics or your neST is playing tricks.

There are much better stats on the market so it seems like a logical thought to consider.

I can’t tell you what I would do as that gets into DIY but it would involve different diagnostics and including the stat in the diag.

 

I am at a loss on what do do next...

Call someone out who knows what they're doing.

You've wasted time and money on a part that you may not have even needed. That particular board is not plug and play, it requires specific setup that you clearly didn't do.