- Joined
- June 3, 2003
- Messages
- 3,293
- Reaction score
- 43
- City, State
- Austin, TX
- Year, Model & Trim Level
- OBD-1 Kenobi
At slow vehicle speeds the fan is important for cooling the engine coolant via airflow thru the radiator and making the A/C cooling adequate via airflow thru the condenser. I wonder if the VLCM monitors the IAT and compares that with the desired cabin temperature versus the actual cabin temperature and adjusts the fan speed accordingly. Or it may just assume that if the vehicle speed exceeds a certain value the airflow thru the condenser is adequate and there is no need to run the fan. I agree with Maniak that most of the fan control problems are integrating the A/C cooling, engine cooling, and fuel economy. I think the electric fan on my 1996 Volvo 850 Turbo Wagon is a two speed (off, low, high) with a fairly dumb controller but seems to work fairly well. I know that it responds to engine coolant temperature. I don't know if it is vehicle speed dependent.
Being older Ford programming, I am inclined to believe the later statement that it will just have predefined values based off inputs (VSS, ECT, IAC, AC Request) and adjust the fan speed accordingly. The VLCM doesnt have any input for EATC stuff (Auto HVAC inside the cabin) so it will most likely just assume when the condensor needs extra airflow based on the PID values IMHO.