Hi!
I know, long time no post etc. 
I have been moving to a new (old) house on the summer, also been on work trips every now and then over 1 month.
Kept me a bit busy, no new lights ATM 8)
Problem: Air ventilation unit (1992)
Does not work properly, I think the problem is in heat relay switch. It has a job of Pausing the intake air to house.
It does it by measuring intake air temp. Now it does not work, ventilation units heat exchanging cells get too cold and freeze from air moisture.
Pic:
It is a Klixon brand.
Problem is I do not know where to get these and I do not know on what heat treshold this is working, since I cannot find proper specs from the net