HVAC System Fails to Operate in any mode

The HVAC Computer is a high-failure item. Too bad the insane engineers turned a once simple mechanical system of levers and ****s into a Rube Goldberg system of complicated, unreliable electronics.

You can start by flexing the electrical connector on the computer just a little. If the computer turns back on and starts working, there may just be broken solder connections on the connector pins inside the module. Those can be resoldered after the covers have been removed. You can also remove and reinstall the connectors. If there's a light film of corrosion on the pins, the scratching action of sliding the connectors off and back on will create a clean shiny spot for it to work for a while.

I'm sendign a pic of fuses in center console. They need to be physically removed and looked at tosee if they are blown. Tehre is also oa relay on the hvac unit by the blower, that may be burnt out. If not you'll have to have your control unit belwo the radio checked for operation.

The computer is the part that turns the heater on an doff
if you only have 2 speeds thenit can be what is called the resistor which is by the motor as well as the relay. The relay controls high speed

See if the resistor is getting power or not if it'snot then your control unit is shot