You may have read how I changed the heater/climate control panel a couple of weeks ago (because the old one drivers side temp control didn't work)-and after I fitted the new one, all I could get was hot air. Tried 'resetting' by disconnecting the battery as advised, took it to the 'experts' (yeah right) who told me there was nothing they could do and blamed low aircon gas, so bit the bullet and bought another panel.
You guessed it-exactly the same. And this panel had the cabin temp sensor with it, so that got changed too.
So someone please explain how I went from a heating system that worked perfectly (apart from having to 'drive' the temperature selection from the passenger side control)to one that seems to think it is freezing in the cabin all the time?
I will repeat at this time-if I select a high temperature eg 26 for a few minutes, then select 16.5, the air temperature cools to something like you would expect....for a minute or two...and then creeps back hotter and hotter....why?WHY? WHY
I can tell you precisely what your problem is, presuming you have a facelift 156 with dual climate control? If you do, read on!!
Exacly the same thing happened to me two months ago, the drivers side control nob wasn't working properly (temperature indidcated would not respond to input, or would go wild and jump up to 32C).
The climate control panel was replaced at the Alfa dealer, however when you do this you must reset the climate control ECU, as replacing the panel sets the ECU to zero function and it needs to be reset. The dealer had initial problems in resetting the ECU: eventually they contacted Milan and were sent an updated programme to get it working properly again.
Did you take your 156 to an Alfa dealer? If not, not a chance in hell of getting it sorted I'm afraid.
Hope that helps. If you need any more details, send me a PM.
P.S. Try and get a refund on the second control panel, as the first is most probably ok - once you get it all working ok that is!!