C5 Rear End Stuck In High Position

[johnway]

Hello all,
My trusty 2002 C5 estate refused to drop it's rear end the other day from the highest service setting. Despite jumping up and down on the back with the engine running and many ups and down with the switch, it just refused to drop. I did not fancy dropping the suspension by releasing the fluid with the car up on ramps so for safety's sake it went up to my local garage. There they put the car up on the hoist and safely released the fluid which dropped the back end. Faulty sensor you may guess....wrong!! The wiring was checked over and the sensor moved to various positions - everything worked as it should so there has been much head scratching as to the cause of the problem. I have not had any trouble since, although I am loath to raise the suspension again for obvious reasons. Any ideas out there?
Regards,
John.