This is usually a stuck relay. Unplug one leg of the low voltage wire at the unit and see if that solves it. If it doesn't then the relay in the machine is bad. If it does then there is a short in that wire somewhere in the home, or a piece of metal is shorting the contacts inside of one of the wall valves. If it is the wire somewhere in the home....have you had any one work on the house recently? Hang any pictures on the wall with a metal nail? If you can't find the short Google central vacuum remote control and you can find a solution that way. If it is the relay you can most likely replace it.
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This is usually a stuck relay. Unplug one leg of the low voltage wire at the unit and see if that solves it. If it doesn't then the relay in the machine is bad. If it does then there is a short in that wire somewhere in the home, or a piece of metal is shorting the contacts inside of one of the wall valves. If it is the wire somewhere in the home....have you had any one work on the house recently? Hang any pictures on the wall with a metal nail? If you can't find the short Google central vacuum remote control and you can find a solution that way. If it is the relay you can most likely replace it.