Why do the hot blowers not work on my Ford Fiesta?

I have recently purchased a 2000 Ford Fiesta Zetec 1.25 and have noticed that the hot air blowers do not come through hot. The blowers themself work fine but they always blow cold air even when at full temperature. This happens even if the engine has been running for 15-30 minutes. Any help would be great. Thanks in advance.Why do the hot blowers not work on my Ford Fiesta?Open the bonnet, look to the right hand rear and you will see a small unit with 2 pipes going into it and 2 going out of it into the car. It also has a small electrical plug going onto it. This unit has gone faulty, takes about 20 minutes to change. Trust me, I'm an auto electrician and have had to change quite a few in the last 6 or 7 years.