Wiring the BMW cooling fan is very simple. Power and ground connections are left totally stock and you only need to connect one wire in the DME box to one of the Holley Grey output wires.
The BMW cooling fans power and ground connections are not modified but the speed control is done by a single pwm control wire.
You will need to configure a custom output in the Holley software to be a PWM signal to control the speed of the BMW fan.
|Holley IO harness
|Pin 8 – black/blue
|1 of the 4 grey output wires
Open your current Holley tune (either via usb cable or pull SD card from screen)
If you have not already, add the IO individual Config from the Toolbox menu:
Select IO icon from the top bar:
Select outputs on the top of the left side menu
Name an output what you would like, in this case, BMW FANS. Check the enable box and select the type as PWM -. Press the Configure button for the output you just made
Select 1 input trigger and configure it for rpm above 400. This will only activate the fan when the engine is running, not with just the key on. This helps not kill the battery. Next click PWM setup button on the top right.
This page you will configure your output PWM table. Be sure to configure the SETUP section correctly. This can be done in many ways but this is a simple example that will ramp the fan speed up with temps and works in most applications. You can see this will send a 60% duty signal to the fan at 167deg and ramps to 85% duty once temps reach 187deg. Configure this as you would like. Stay about 90% duty for max fan speed.
Now that your output is configured, you must map which pin you have your fan wired to. Select the PIN MAP icon from the top bar then click view outputs
From here you will need to drag and drop your BMW FANS output to the correct output. You can determine which output you have your fans wired to by using this:
In our case, we removed all the default configured pin outputs by dragging them back to the unassigned outputs area, then dragged BMW FANS to the pin b12 output.
That’s it, now your fans will operate as you programmed in the PWM table.