e36 heater problem
 

Hi I own a 1997 316i coupe with automatic climate control,my problem is the drivers side works ok at whatever temperature I set,but the passenger side will only blow hot, the climate control module on the facia appears to be ok as I have tried a friends working module and it made no difference.any suggestions appreciated

This is probably not the solution, but it is very easy as a first thing to try.

On both sides of the climate control display is an air inlet where the control samples the temperature. That air passage tends to clog with dust. If you have a can of compressed gas that you use for blowing dust out of electronics, you can blow that through there to see if it will help.

The problem is more likely a damper valve beneath the dash, but that will be a lot more involved to check and correct, so try the easy stuff first.