Hello all 

My partner has a mk1 1.6 Focus and her AC has been playing up.

On fan settings 123 the ac compressor will work but the fan won't (what litte air that is coming through though is definitely ice cold)

On 4 the fan will work but the ac won't. You get a initial rush of cold air if it's been sitting in 1 2 or 3 and you change it to 4 but after that it's just hot air 

Your fan problem is the classic sign of a failed speed control resistor. I suspect the aircon is not cooling very well and might need a re-gas. It can cool with very little airflow but as soon as you get a full blast it can't cope. You just get an initial blast of the cold air that's been sitting around the evaporator.

Thanks Mjt any clue if this is a off the shelf part that is easily replaced then I can re-gass myself? or is the resistor a mission to get to

I wouldn't recommend attempting to re-gas it yourself. If you take it to someone like Kwik-Fit or an aircon specialist they will remove the old refrigerant and do a vacuum and pressure test for leaks then re-fill with the correct type and quantity of refrigerant and oil. Your partner's car probably uses an older type of refrigerant and it's important to use the correct one.

I think the resistor is located somewhere behind the HVAC control panel but I've never had to access one so can't be sure. Hopefully one of the experts will be along soon to help with that. I think the parts are still available, if not from Ford (likely at an extortionate price) then from the usual internet marketplace.