Central Vacuum works when power switch on ...

DOes it not work on any of your wall inlet valves? If all wall inlets appear dead take a coin making a connection with both of the contacts inside the throat of the valve. If the vacuum turns on the problem is in your hose or the powerhead. If nothing happens plug in your hose and try wiggling the low voltage wires at the vacuum as you leave the hose plugged in with the swich on your in the "on" position ( if you have a switch) If still nothing unscrew all valve plates from wall leaving wires attatched. Inspect all connections for loose wires or wires that have come off terminals. .