2003 Buick Regal Climate Control Module

If the symptoms before the replacement, and the symtoms after replacement are different, I would suspect that the module may be defective. After reviewing the schematic, the only items the climate module directly controls is the temperature actuators, and vacuum control solenoids for mode. The blower motor is powered through the blower control processor, so a blower drawing too many amps would take out it. The compressor is controlled by the PCM, on bus communications messages from the climate module. You first may try disconnecting and shorting the battery cables together, and see if that restores operation. From there a scan tool would be advisable, to see if you can establish communications with the climate module. By stating that you have power to the buttons, how did you determine that, is it because they are backlit? You can check power and ground to the climate module, the two power sources to the module are at pins C12 which is an orange wire hot at all times, and pin C5 brown, which is hot in key on. The ground is at pin C1 black wire. You can use a voltmeter from C1 ground, to each pin C12, and C5. You should have near battery voltage in both cases. Since this climate module was so much cheaper than the dealer, is it still a factory part, and was it new or remanufactured? This is all assuming that you have an automatic HVAC system. If you have a manual system, there is some differences.