Heater Fan/Blower P38a

My heater fan/blower is running constantly and can't turn it down! i have removed relays to see if it was that, swapped them around not that. any ideas where to start to sort this problem out..........cheers

Speculation rather than speaking from any kind or experience or particular knowledge...but I believe the control knob to adjust the fans' speed is connected to a potentiometer (Potentiometer - Wikipedia, the free encyclopedia) and maybe that is faulty.

Although not dealing with that problem, this page details how to get at the gubbins behind the heater fan control knob on the HEVAC control assembly: LCD Backlight Repair.

Hope that helps you get to the bottom of this...

Malcolm