No heat in my Caddilac

The thermostat may be stuck or your heater core may me blocked.

Could be a few things. There is a damper that lets the air flow over the heater coil. It may be stuck. Not sure about your particular car, but some have a valve to control the flow of water do the heater core. They may be inoperative. Considering the age of the car, it is possible the heater core is plugged up with gunk and not passing water.

I'd warm the car up and see if hot water is circulating to the heater as the first step. Then you can determine if it is a water flow or air flow problem.

...or a vacuum hose may be off or a hose may be collapsing...

Your car has a heater water valve that is controlled by vacuum. Vacuum is controlled by the programmer solenoid valve in the BCM. The heater water valve is located at the right rear of the engine compartment. It's function is to pass/block the flow of coolant to the heater core. A quick check would be: engine at NOT/EEC in Econ at 90=B0 temp/both heater hoses are hot to the touch. If neither hose is hot: valve faulty or problem with the BCM. If one hose hot: no flow through the heater core. Both hoses hot but no heat: problem in the plenum system.....probably a vacuum motor or vacuum control problem. Hope this helps.

Dave S(Texas)

Take it to an garage , big shot