When I arrived the main operators were not in the building but I checked it thoroughly without finding a fault.
When the two operators arrived they more-or-less called me a liar and said that they would demonstrate the fault.
The machine was switched on and the chap blocked the end of the hose with the palm of his hand and after the vacuum had developed, pulled his had away and said "Look, the suction has stopped".
The reason was immediately obvious to me and I opened the recovery tank an showed and explained the ball-and-cage high level shut-off. The sudden unusually high airflow he was creating actuated the valve and shut off the airflow.
I had to go through the explanation several times and even let him repeat his 'palm-flapping' with the valve removed to further prove my point.
He did say that he was going to remove the valve permanently to 'solve' the 'problem'and I spent a further 20 minutes explaining why tat was a very bad idea and that it was easier to break the pointless bad habit and to use the machine properly.
A few weeks later I got an email saying that the machine had developed a bad leak, had smoke coning from the machine and it constantly blew fuses.
My reply was uncharacteristically terse and I asked if it was true that he was Englands' only living brain donor!
The JAGUAR MX-2 ETM @ cross-american.com