Cabin vents always blowing?
01-03-2020, 07:05 PM
#1
Three Wheelin'
Thread Starter
Cabin vents always blowing?
Everyone's favorite topic, the heating and cooling system of our 964s! As a background, my a/c was not functioning when I purchased the car and I currently have the a/c belt off after I completed the RS fan hub installation. I have also installed the RS heater duct, thereby removing the blower assembly. After reading lots of posts from members re: what to do with the relay, I purchased the bypass relay from Porsche (p/n 964-610-184-00) and installed it to see what would happen. As luck would have it, it works! It restored all of the fan speeds for me without having to wire or jump anything. For those interested, I did not remove the 30A fuse, just put in the relay and my car is a MY 90, build date Dec 1989.
Now my question is re: the cabin fans. Even with the CCU fan setting at 0, they like to blow low to sometimes moderate amounts of air. The amount varies but ranges from a slight trickle up to what feels like an equivalent fan setting of 1 or 2 sometimes. If I then turn the fan on, the air increases proportional to the setting as I would expect. At first I thought it was always hot air blowing but today found that rotating the temperature dial kicks in the mixers so that on full hot it's hot and full cold it's outside ambient air. Air is coming from all 4 cabin vents. Do these symptoms point to the left and right mixer servos that require attention? Lastly, I should note that my footwell servo works great but I know my defrost servo for the windshield does need servicing.
Now my question is re: the cabin fans. Even with the CCU fan setting at 0, they like to blow low to sometimes moderate amounts of air. The amount varies but ranges from a slight trickle up to what feels like an equivalent fan setting of 1 or 2 sometimes. If I then turn the fan on, the air increases proportional to the setting as I would expect. At first I thought it was always hot air blowing but today found that rotating the temperature dial kicks in the mixers so that on full hot it's hot and full cold it's outside ambient air. Air is coming from all 4 cabin vents. Do these symptoms point to the left and right mixer servos that require attention? Lastly, I should note that my footwell servo works great but I know my defrost servo for the windshield does need servicing.
01-04-2020, 10:12 AM
#4
Rennlist Member
The 964 Climate Control Units with part number ending with 00 do not stop the two main blower fans completely, the fan speed is the same at "1" and "0" settings.
The units with part number ending with 01 stop the fans, as all the 993 units do too.
Cheers,
Tore
The units with part number ending with 01 stop the fans, as all the 993 units do too.
Cheers,
Tore