heating problem

I have a 1994 mercury grand marquee that has no heat. All the hose's are very hot changed the thermostat but no heat in the cab, can anyone tell me what the problem is.

I think this year uses vacuum to control a vacuum motor on the blend door.
Start at the motor and make sure your getting vacuum to the hose. Follow the hose to the fire wall. A lot of these has a rotary vacuum switch behind the knob to adjust it. Look under the dash and check if you can see it. Watch with a flashlight and make sure it moves. I've had to replace them on older vehicles.