You blower fan is control with what is called pulse width modulated. That means the control module sends a varying level of voltage depending on the speed you want the fan to spin.
So if you are only getting high speed then I suspect the A/C amplifier is your issue assuming you have auto temperature control. If you have manual temperature control, it is not much different but the controller is called the front air control module. However, it is still PWM.
This is what controls the speed once the Body control module grounds the relay to turn the fan on the amp actually controls the speed.
Let me know if I misunderstood something but it appears this is what needs replaced so I included the process. Thanks
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Tuesday, May 25th, 2021 AT 11:29 AM
(Merged)