I installed a Hunter Auto Saver 550 in my home recently. Everything seemed to be working fine as the heat worked and that has been all I needed. Now that it has warmed up here and I need AC, the unit does not respond. I set it on cool and nothing happens. Even when I move the fan switch to "On" instead of Auto, it does not respond. Any ideas for help here? I made sure that I moved the switch on the internal part of the unit to the "O" setting because I have an orange wire.

If your system is a heat pump, it needs 2 signals to provide A/C. The orange wire usually runs to the reversing valves. You also need a signal, usually using a yellow wire, from the Y terminal to the air handler and outside compressor to start them up. Check those connections.

I have a twist on this same problem. Same thermostat unit, and same issue (controls heat, but AC won't switch on now that the seasons have changed). But, I don't have an orange wire. Seems like it's a typical 5 wire setup. Gas heat and elect AC.

Anyone have advice? It's starting to get pretty warm here in Texas...

Check the sticky at the top of the forum. Last fall we had a great new member show up. Northern Heat was quickly appointed H&AC expert, and set up what I think is the best sticky on AMHD. If you don't find your answers there, post back.

Thanks for the tip. Unfortunately, there isn't anything in the sticky that speaks to my issue.

The furnace worked flawlessly, however the AC refuses to function at all. I originally replaced our old thermostat (the Honeywell installed when the home was built) because it threw out a "bAt lo" error and then freaked out (random flashing on the LCD). I replaced the batteries, however this didn't fix the issue so I replaced the thermostat (I should note, I tried re-installing the old thermostat, and it worked briefly then threw out the same bAt lo error and the LCD freaked out; again, the batteries were new).

All was good until I needed to run the AC. Again, it ran briefly when the old thermostat was re-intalled, but doesn't even respond when the Hunter Auto Saver 550 is up.