Electrics and temperature

I have 1986 MB 420 SLI, with the recent cold weather the climate control has been acting up. When I first start the car I can not get the unit to work, no fan nothing. I have so far been able to get it working by letting the car warm up and then shut it down and restart it. When the system does kick in it begin with a cliking noise from behind the instrument panel and the recyle air light going on and off along with the fan. The other morning after getting it going I began driving with it in this state and when I steped on the brake or put on the signal light the system shut down and I had to restart the car again to get it going. Does anybody have any idea what might be going on here, is it the climate control unit acting up? Or is there an other component in the electrical system that is failing ?

Assuming that it’s not something obvious like a fuse, it’s usually the climate control (push button) unit that causes that type of failure. You can either replace it with a new or rebuilt one, Some folks try to take them apart and re-solder all the electrical connections (with some success).
Here’s one for about $300:


BTW, I assume we are talking about a 420 SEL?