A/C and heater doen´s work at all... Where to find a HVAC programmer? on 1991 Buick Park Avenue

Nothing in the HVAC system is working - no heat, no fan, no A/C. Have replaced A/C control unit in dash and then the passenger A/C control panel in door, but the system is just not responding. The panel (in center dash) is completly black and silent.... We can´t even see the outside temp on the panel.
What to do? Someone suggested to replace the HVAC programmer but, we can´t find one anywhere. GM discontinued it...

Asked by for the 1991 Buick Park Avenue
Contact me at I can find what you need.
1 more answer
Star by checking your fuse. Then check the Power to the system and check your grounds. Once you have established power you can trouble shoot further. Make sure the radiator is topped. If it is not that can affect it.