Heater control unit changes by itself.

[krisgrant311]

Not sure if this is normal but if I put the heat up or change from the footwell to windscreen vents, the blower will speed up by its self, will do a few bars every minute and before you know it its almost on full. Could this be a fault in the unit itself?

Also I can hear the servos that control the airflow direction always adjusting them selfs, even when the ignition is off the right side heat servo is still making a noise.

Can anyone help with this or had similar problems?

[nevo]

If you increase the temp the blower should increase for a while until the higher temp is achieved,however if it still ramps up, it cant reach the set point,looks as though you've got a sticking flap motor,you say the righthand one is giving problems(I assume the one on the drivers side)thats the heat flap(yellow lever)remove the motor and operate by hand and see if that increases the heat.

[krisgrant311]

I tested it today and both sides do heat up fully, both sides are the same, and it gets really hot so I don't think its having a problem reaching the set temp. Im just wondering why the motor adjusts its self all the time.

[nevo]

Check the pollen filter,remove it and try it out maybe its blocked not allowing enough airflow through,still think the blower is chasing the setpoint.

[Steve0217]

Hey I know what your talking about, my HVAC does this also. I played with it a bit and from what I understand, your temperature setting has a fan speed memory. For example: If you have your temp set to 27 degrees. and your fan on full blast and then turn the temp down to 25 degrees and turn the fan down also, when you return your temp back to 27 degrees, your fan will automatically turn back up to full (the last speed it was set to at 27 degrees) Hope you followed! :D