Im no expert, but i guess working through this logically may yield a result.
First thing to check is wether the aircon pump is getting power?
If you have access to vcds it may help.
Start by testing the signal from the ac button on the heater panel (output tests in vcds may help).
From there it will probably route through the fuse box (check the fuse) and then to the aircon pump.
You could check their is power at the pump itself with a multimeter?
Ive not tried any of the above, but its a start?
On mine, the electrical connector on the aircon pump is held in with a circlip (and so normally part of the pump). Mine had been smashed off somehow (previous owner).
Worth a look and making sure that connector is intact and the loom is attached to it securely?
Any further codes in vcds?
Jas