Unable to run fans


New member
I have the 635 display combined with the SCAB board but my fans will not run. Is there a setting or several setting that need to be set and if so where?

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Last edited:

CF Mark

You mean the fans youve plugged into the SCAB module dont run at all?

Fans plugged into a SCAB should always start up when power is first applied to the LCD & SCAB.

CF Tech

The exception is if someone has set the default boot state of the fans to 0%, or if the firmware is a custom build that has the fans set to 0%.

As an aside: the module will boot a little bit faster if the fans are all set to 0% as a default boot state. If the fans are set to be on at boot time, the firmware sequences turning them on one after another with a little bit of delay so the start-up current spike is not as big as it would be if all four were started at once.

If that is the case, you would need to send command 17 to set the fan power to something other than 0%.

Once you have set the fans to the power level you would like, you can again make that the default boot state by using command 4.

Please see the "Command Codes" section of the CFA-635 data sheet:


Please also review the "FAN CONNECTIONS" section of the SCAB data sheet for a better understanding of how the fan control works, and recommended settings: