Okay, I have done some more investigating today. the pump runs as it should, and when it should. however it still only pumps up one side. I have opens the the compressor housing and checked voltage on on both plugs for both solenoids. Both are at approx 12Vdc when the pump runs. I then removed both solenoids and both operate as they should. Now the solenoid operates the spool valve to let air fill up the air tank. I think i can now only assume that the although the solenoid is operating the spool must be seized into position preventing that side from inflating. So it must be reasonable to presume the signals are good and it is a bad spool valve. Any thoughts??

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2001 X5 4.4i Sport
Alpine White
Black leather Interior