All the info is in the very first post. Stock replacement fan is adequate, I live in the hot ass desert and it works perfect. But you just remove the Aux fan to get proper airflow. I constantly monitor the cooling temps with my UltraGauge and it's always between 192-197 degrees. Yes this is a simple swap fans and plug it in. The biggest part of it is removing the Aux fan as the front bumper has to come off to get it out. It's pretty easy with two people. Fan nut is just for bling factor.Originally Posted by TigerTater
Here is how the fan is controlled:
The electric cooling fan is controlled by the ECM. The ECM uses a remote power output
final stage (mounted on the fan housing). The power output stage receives power from a
50 amp fuse (E46 - located in glove box above the fuse bracket). The electric fan is controlled
by a pulse width modulated signal from the ECM.
The fan is activated based on the ECM calculation (sensing ratio) of:
• Coolant outlet temperature
• Calculated (by the ECM) catalyst temperature
• Vehicle speed
• Battery voltage
• Air Conditioning pressure (calculated by IHKA and sent via the K-Bus to the ECM)
After the initial test has been performed, the fan is brought up to the specified operating
speed. At 10% (sensing ratio) the fan runs at 1/3 speed. At a sensing ratio of between 90-
95% the fan is running at maximum speed. Below 10% or above 95% the fan is stationary.
The sensing ratio is suppressed by a hysteresis function, this prevents speed fluctuation.
When the A/C is switched on, the electric fan is not immediately activated.
It is run from 10 HZ to 100HZ a scope is the best way to see the signal. You can command the fan by creating a signal or using the RIGHT scan tool you can tell what speed you want it to run at and measure the HZ with a scope therfore checking you DME output.
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