W 126, 420 SEL Heater and A/C problem
 

I got 1986 420SEL American Edition, and i have some weird problem with heater blower and A/C. It goes ON and OFF by it self, but when i start a engine i heard some relay click from passenger side, somewhere under the dashboard. I was driving a car and the heater goes on , then goes of by itself.

Please, if anybody can help me with this issue ill be appreciated.

Thank You !

How is the control head? Try to isolate the fuses and relays associated with the climate control blower motor. You could possible have a wiring problem, sticking relay or faulty control head.

I have a 87 420SEL at one point. One day the blower motor would just come on by itself. I would even Press the "O" for off and nothing would happen. Problem ended up being a faulty control head.