Carrier ac system in my upstairs zone, the outdoor unit is functioning but the air handler in the attic is not working. I removed the programmable thermostat to bypass and see if the blower would go on- nothing happened. COuld the system be overheated since we are having a record heat wave here? Suggestions on what the problem may be. The filter definitely needs to be changed but that has not solved the problem.

First I'm no HVAC expert, this is based on personal experience. On the air handler there is a circuit board, our goodman blew the 3 amp(blade type automotive). I would start there. We are burning up here in St Louis. Not long now winters coming. Good Luck.

Thanks for sharing, however, if the 3amp fuse on the control board were blown, the outside unit would not kick on as the low voltage from the airhandler supplys low voltage to the outside unit to close the 240v contactor, so we know there is power to the air handler and the low voltage side is working also. Next step is to open up the unit and check to see if you are getting power to the blower motor. Could be a bad motor, or capacitor, or a bad fan relay(which on many units would mean you would have to replace the whole mother board). Some trouble shooting needs to be done here for sure. If you are handy with a multi meter, you should be able to diagnose this yourself, if not, you will most likely have to get an onsite tech to check things out for you. I would doubt that the heat in the attic would cause the motor overload to trip, at least Ive never seen it and we see well over a hundred degrees in our area during summer months. Good luck and please let us know what you find.