Have HVAC Questions? Ask an HVAC Expert for Answers
Hi, I'm Tim and I'm an HVAC expert here to help answer your question(s). Please provide all the information I ask for since I'm not onsite. At the end of our dialog you will be asked to rate my service, but please wait until then and all your question(s) have been answered satisfactorily. If you are not satisfied, I'd appreciate it if you'd tell me why before leaving a negative rating and allow me to continue to work with you until we are able to both agree on an outcome to follow. Thanks for your business! On the Aprilaire 8400 series thermostats there should be a button right next to MODE. This is the button you would press the the desired thing, HEAT or COOL depending on what you are calling for.
You may want to check your furnace or air handler first since this supplies power to the thermostat. Could be a blower door not on tight, blown fuse on the board or power switch turned off.
Try reseating it on backplate. Perhaps some of the pins are not making contact.
If you have a votmeter, I can help you quickly determine if it's the stat or the furnace.
OK, well if you need further help, let me know.