climate control issue

[tristan]

Hi got a problem with teh climate control in my B5

all works fine from cold as car heats up and i take the heat away from the windscreen, the blower slows andi leqave it in auto at say 28 degrees.. but the car is freezing inside and the climate control doesnt seem to kick in by its self i find im putting the heater upto high and increasing the fan speed, then its all good, car is toasty warm, put it back onto auto and it slowly gets colder again,, is there a sensor i can clean or something else i should check???

i have noticed a lot of fluff, dust on the right hand vent on the climatronic control. ???