1980 450 sl
 

I have a 1980 450sl german spec car that is not pushing any heat (cold air only)through the control panel. All of the setting/buttons are working but no heat. I have read threads and tried several things like disconnectinting the monovalve connection (didnt work). I have disconnected the heater hoses hot both sides and good circulation, fuses look good ,
Any other ideas? I have searched the threads but not finding a fix. Any help in pointing me to the right thread would be appreciated.
Thanks Richard

I should mention that the temp is sitting around 80-90 degrees