Hi Adam,
the Haynes manuals are more general in nature.
You need the GMC Service Manual CK8 Truck, it is $120.
Please be sure that the compressor is at fault, there are 30 pages of diagnostics procedures in the GMC service manual.
As usual, most of it is: Use the scan tool, send a command here, check the result there.
You do have a Suspension Control Module under the Auxiliary Blower Motor.
There is a Compressor Leveling Module (a box with the compressor in it) on the Rear Crossmember Frame.
Do you have any DTC's?
Hope this helps, take care, Eggert
