I know this is an old post but determining blower functionality does not need to be blown up into a complicated science project. It shouldn't be dependent on outside temperature either. If you are working with an automatic climate control; select economy mode then depress the fan push button and cycle through the calibrated speed steps. If the fan does not function in this mode, jumper the blower +/- leads to 12VDC/return respectfully. Hopefully at this point the fan won't turn, as replacing the fan is way easier than tracing out an open circuit or a digital component failure.