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3 wires fan to link g4+

EFI Wiring Fundamentals

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Discussion and questions related to the course Motorsport Wiring Fundamentals

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I made a relay to switch my fan on connected 30 to +12v 87 to fan +12v 85 aux 86 to +12v switching the relay works good but when connecting my fan it doesn't work they told me that it had an internal ecu (bosch 1137328118) I'm wondering how to make it works

I'm not familiar with that particular fan, but looking at a picture on google, it seems to have 4 wires, which could indicate it is PWM controlled, like a solid state relay.

That is a PWM controlled fan. It will need power, ground, and most likely a PWM- signal from the ECU. These fans operate at variable speeds and the speed can be configured based on CTS. Here is a much too long read, but I recall people talking about the BMW fans specifically in that thread:


I just installed the 850watt fan from a 6th generation Camaro and am using it on my LS powered 67 Mercury Cougar.



This may, or may not, help.


I tried connecting it directly to battery terminals one wire to +12v the second to batt gnd the third to ignition 7 output and tested it (pwm with 300hz and 10hz)and it doesn't work

Ignition outputs dont have an internal pull-up resistor. You will either have to wire your own external pull-up resistor, or swap to an aux output pin.

Thank you Adam I wired it to aux 1. when testing as pwm with frequency 300hz it works when putting it as a gp pwm with constant frequency 300hz and 1 Cond only which is ect> then it doesn't work so what is that when testing it as a pwm it works when adding it as a gp pwm it doesn't work???


If you re-worded that second to last post so it was understandable, and made clear what you were querying, you may get a response.

In test PWM mode the output will be forced active with a 50% duty cycle, in GP PWM mode the output will only become active when the specified conditions are true and the duty cycle will come from the GP PWM table. The aux status will show "Active" if its conditions are met and the table crosshairs will show what DC is being output.

I have configured these fans using various Holley EFI systems. When setting up the output it must be a PWM- signal, at 100Hz, and the output must use duty cycle as the units.


On top of setting up the frequency, you also have to setup the duty cycle table.

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