I have a 2005 focus ZX4SE. The a.c. does not blow cold anymore. What are some of the steps I should check?

compressor could be bad,a leak in ac system,or it could just be low on R-134A.

the evaporator. also the the switch sometimes goes on it also it still lights up. well that was mine anyway

evaporator or known as dryer is not the problem.

Just check to see clutch kicking in. First then will know of leak in system. Or high low pressure switch. Check power at clutch if not check fuse!

I know this sounds silly, but a common fault with the Fords of this era was the heater control solonoids, basically electrically controlled valves that had a tendancy to stick open slightly, costantly allowing hot coolant into the heater matrix. This is usually found close to the bulkhead , with the heater in the cold position start the car allow to reach normal running temperature and cautiously check to see if the rubber hose is the same temperature both sides of the valve, if it is your valve is not sealing properly and should be replaced, a relatively inexpensive item Approx £35 for the part and no more than an hours labour!!