Please help... It's hot at the moment in Minnesota( I know that's rare), but my AC won't kick in.. I have a Honeywell Chronothermo III and in the display, it reads -AC.. What does that mean, and how do I get rid of that? Thank you

Do you have a users manual or installation guide? It could be that there is a bad connection to the blower controls or compressor relay. One of the relay coils could be open or shorted. You could also go to the furnace and jumper the R terminal and the Y terminal, and if both the blower and compressor come on, the problem is the thermostat or the wiring from the furnace to it.

Labman.

I jumped the Y and the R as you had said, and the blower kicked in. So, my next step is to test the wiring from the furnace to the termostat and/or replace the termostat? Thanks


Airalpha

You also need to check if the compressor outside starts. If there is a problem with its relay coil or wiring, that is what the thermostat is telling you.