Heating problem

[waynester]

The heater in my wifes Fiesta 1.25 zetec ('97) has suddenly started blowing cold air? It's a 1 owner, with 37,000 mile's.
The engine temp is perfectly normal, the needle swings round to the same spot it always has, and does not over heat, so i'd like to rule out the thermostat.
What does feel different is the resistance on the cold/ hot knob when turning. I tried removing the fascia surround and stereo to have a look. How is the knob fixed..glue?
Could't get stereo out either, and i was using bits of coat hanger wire pushed into the 4 holes to release it...nothing, would't budge!!
I'm reluctant to put the car into a garage/Ford as i'm sure the problem is simple, just typical that this happens now with the weather as it is..

Any ideas greatly recieved..

[nighthawk]

Have the heater bypass valve checked/replaced.

follow the rubber pipes from the engine into the car at the bulkhead, they'll pass through a valve block with a small motor on, before the pipes enter the car.

common for them to pack up, failing that FMC released a comprehensive TSB for diagnosing these systems a few years ago, sometimes it's the electronic control panel, but not often!!!

hope it helps