Today I replaced the following on my 1987 300D ACC system:

1) Push Button Control Unit
2) Vacum change over valve
3) sampler motor for inside temp sensor
4) all 7 vacum actuators

I also checked the temperature sensors by following procedures with an Ohm Meter according to 83-604 in the service manual (Checking electronic components of the automatic climate control) and all sensors are in the specified ranges.

My blower motor is always on! When I hit the 2 fan speed buttons on the PBCU, the speed will increase a bit or decrease a bit. When I hit the 0 button, the fan still remains on.

Any suggestions?