There are 6 possibilities, here are the 3 engines with A/C...
Consulting your owner's manual should give you an idea of how to replace
a belt depending on which belt it is that needs changing. Assuming it
is the timing belt that needs to be changed it is a simple process to
undertake, though if you are unsure of working on motor cars it may be
better to take the vehicle to a garage for professionals to carry out
Firstly check your owner's manual for the recommended mileage for
replacing your timing belt. Replacement for a Ford Focus is at 120,000
miles. You need to locate the timing belt and examine it for breaks,
damage, fraying, worn spots or looseness.
Disengage the negative battery cable in all models. Detach the passenger
inner splash-shield and wheel cover, the accessory drive and timing
belts, the tensioner and the crankshaft pulley. Remove the spark plugs,
catalytic converter and idler pulley in 2000 and older Ford Focuses.
Undo the retaining fasteners and lift the timing belt cover off the
engine. Align the crank and camshaft timing marks. Older models call for
undoing the water pump pulley and valve cover before locking the
camshaft in place. Release the tensioner's bolt. Turn the arm to the
right 14 degrees and place a 1/8 inch drill bit in the opening. This
secures the belt tensioner in place; you can now take the belt off.
Once you have fitted the new belt you can re-assemble the parts which have been removed in the reverse order.