I've 2001 Focus diesel, the heater is just blowing cold air, turning the control knob makes no difference, it was ok till recently, any ideas, thanks John

Engine thermostat seized? Low coolant level? Is the engine temperature in the normal range?

Heater control cable broke  could be a number of things 

Engine temp and coolant level correct, I was thinking about the control cable, any idea where it's situated on the engine, I was wondering it couldn't be an airlock by any chance, thanks for the replies

I think I'm right in saying that the cable just goes to the heater box so not connected to the engine. The matrix always has hot water going to it and the cable just moves a flap. With it all turned off try just moving the heat control dial and listen for moment in the heater box. You should be able to hear something move. The cables go down the drivers side of the box and you should be able to see it move if you take the lower panel of the dash off under the steering wheel. 

Thanks for the info and going to the trouble of adding the photos Michael, I'll have a look when I get a chance, thanks again much appreciated

No problem buddy, I think it's the black control end you need to look at, if it moves then that will direct heat into the car. Have you checked the hoses going into the heater at the back in the engine bay? Check the both are hot. If only one is then it may be a air lock.

Just had a check and with the fan on 4 and turn heater control from cold to hot there is a big difference in the sound of the fan, like it was redirecting the air?, I could only get to the heater hose that runs along the bulkhead this felt warm, is it possible to remove a panel in the dash to get to the matrix to check if it's getting hot, what would be the easiest way to release an airlock, another thing that  I've just thought of which might be causing problems, in August when I removed the undertray to change the oil and filter I noticed the bottom hose going into the rad had a slight leak so I added some radweld which cured the leak, I'm not sure if this could block the matrix, although the temp always remained normal 

Have you try disconnecting one of the hoses from the bulk head with the engine ruining

i did this once to remove air lock and it worked 

 

Hi dezwez I've only just got round to having a go at sorting the problem, the hose from the heater to the engine next to the oil filter remains cold the other hose from the heater to the cylindrical "thing" at the rear of the cylinder head is hot, what is the correct name for this cylinder. I'm going to disconnect the hose by the oil filter to see if the water runs out, if not I'll  disconnect the other hose and try flushing out the heater matrix