Ford KA Heater Problem, Very hot Heater resister unit?

Help.
I have replaced the Heater control valve, it works now i think... I swich the car on, and it moves the sellonoid valve to the closed position, no hot water can pass through.
However, I also replaced the heater resister unit, the one near the passengers right foot, but it gets very very hot, to the point I think is beyond normal... I know it got hot because i tested the heater system before putting the resister unit back into its well, with the single screw and black plug with 4 wires. Still no hot air when I change the heating selector. Still a problem... need some advice please