Join Date: Aug 2004
Location: Auckland, New Zealand
Re: 156 heating/cooling problems
I'd go with David's suggestion - I had to deal with this on mine, and I've read many posts about it. It appears that the housing for the flap that directs the air up or down distorts, so the centre edge of the flap nearer to the rear of the car sticks on the housing, and will often not open to let air upwards. Sometimes switching to hot air will let it come free, or a bump in the road will shake it free.
Remove the two allen head bolts in the centre vent, pull gently upwards (there are clips also that will release), unplug the wire from the alarm flashing light, and you will be able to look down in and see the flap.
Lube may help, but in many cases including mine it may be necessary to take a sharp knife and slice a few mm of rubber off the edge of the flap where it jams. Fixed.