Climate computer loosing it’s mind?

I read quite a few complaints about the heater system. Not that it’s a bit underpowered, but really off, as in just blowing cold air when heat is requested. I am more or less trying to compile a list of user-fixable, or -detectable causes, from what I read on forums. Please comment if any of what’s listed here is wrong by your experience, or right!

• Low on coolant gas. Rattling sound by the compressor. Dealer trip needed. CanZE might help, it shows the gas pressure after the compressor. It should be around 4-5 when idle and around 20 when working hard;
• Cabin sensor. It is at the bottom of the rear view mirror mount on the wind shield;
• CLIM computer bug: it is said that in combination with or after a demist, the car can refuse to heat. I am not sure if a hard reset (next bullet) is needed, but one could at least switch de-misting off;
• CLIM computer lost it’s mind. Things happen. Pull/push fuse F3. It is the rightmost column, the first fuse counting bottom up in the fuse panel in the cabin. Should be a 10 amps fuse.

Some people have reported heating the outside temperature sensor to roughly 50 degrees using a hair dryer or a hot towel (it’s the dimple under the right hand side wing mirror) also seems to kick the computer’s logic.

Edit: see this post for a follow up.