The ac and heater don't work - 1996 Cadillac DeVille

check for power and ground at the motor. which ever one your missing you will have to check where the loss is from the motor back to the heater switch to find the problem. have you checked the fuses as you don`t say.

Check radiator, the fluid went somewhere.

the water heater control valves are front right down low behind the radiator and are electricaly operated ,the AC pipe that runs under the engine but above the sub frame could be corroded out as this is a common fault with these cars ,also the electrical solonoids that shut off the heaters can corrode up as well but i have known them to stick open.

Both "blower" fuses are fed by the ignition switch. If there is no power to those fuses than the switch is the likely problem.

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where 2 find d ac fuse

Just a stab at it................see if there's a vacuum or electric operated valve in the heater hose lines.Trace it out.The heater hose goes from the thermostat area at intake manifold thru the heater core,and back to water pump area. don-ohio

Blender door not working on heater/AC box.OR.....it's a severely plugged heater core.don-ohio

Yes,your blower motor resistor is faulty.

you need a resister found under your air duct by the passenger floor under dash board auto zone sells these for about 25.00 you may as well buy cabin air filters while your at it . 1 of the screws will be a pain to install back into the duct work I left mine out didn,t make a difference . you might have to order it as they are a comman item oh you will need a vacuum to clean up mess from cabin air filters .this is not a hard job .