Intermittent heating and air fan in 1999 cadillac deville.

SOURCE: '96 cadillac deville has no air.cond./heat

Unfortunately for you ( i had the same problem) The A/C compressor HAS to be in working order on these cars or else all heck breaks out with the climate control.

If it's a nice car, get a new compressor installed. If it's borderline- get rid of the car.

I paid 2200 to Cadillac to fix the A/C and climate control only to have the transmission fail in my '93.

I dumped the car soon thereafter....

SOURCE: 1999 cadillac deville air wont work

There's a blower motor (fan) under the hood and up against the firewall near the center of the car that takes some work to remove. It has gone out in the last 2 of my 4 Cadillacs. Turns out if you're not real careful with the positioning of the spark plug wires they will brush up against it, and if one of them gets cracked or brittle it will "arc" and short out the blower motor. The a/c compressor should still come on (you'll hear a click when it engages) but you won't get any air blowing into the cabin, hot or cold.

The part was like $200 stock (year 2000 prices) and it took about an hour to remove it. My Caddy at that time had this damn strut bar going across the engine bay which we eventually removed to get to the blower motor.

SOURCE: 1995 cadillac deville 4.9 eng no heat

The heater in your car depends upon a flow of hot coolant going through the heater core in order to get hot air into the car. If the heater core is partially plugged, it will restrict the flow. If you have a head gasket that is putting exhaust into the cooling system, it will eventually get into the heater core. When this happens there is no coolant in the heater core to make the air warm. If the water pump vanes have corroded away the result will be very poor coolant circulation causing the heater to not blow hot air. If your car is equipped with a heater control valve that is not functioning properly, the coolant flow will be restricted. One or a combination of these factors is likely the culprit in your case.

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SOURCE: thermostat location on a 1999 cadillac deville concours

looked it up online and looks like it's on the front of the water pump in a thing called the coolant inlet housing. one end of it looks something like the letter y and the other end, where the thermostat is round. hope that helps

SOURCE: 1999 Cadillac Deville and the radiator fans are not coming on

you should check the fuse in the fuse boxe under the hood and find the radiator fan fuse
if the fuse is no longer good the little piece of metal will be cut in the middle so replace it with the same number if it's a 20 AMP do not put a 30 or a 15 AMP
if the fuse is good then there might be some problem with wires (could be cut) or the radiator fan motor is no longer good
you should have it check
Good luck