Climate control
 

I have 1980 SD300 turbo. I cannot get any heat .I checked Bosch circ Pump and it works as well as all fans and buttons and selector on console. If it is the control valve with all the vacuum hoses and wires how do I trouble shoot that to make sure that is the problem ? or can I bypass it somehow by redirecting hoses?
Ay help to point me to information would be appreciated. Thanks

Do a search on this topic. It has been discussed to no end because the AC/heat system on older Benzs weren't particulary the best or most reliable.