The reason why a machine makes sounds in "standby" is a leak, which causes the machine to restart occasionally to build pressure back up. If it is a big leak, the machine will run all the time.
If you do not see a leak, this may be because the leak is taking place inside the machine, from the high-pressure side to the low-pressure side. Often this can be caused by some debris blocking a valve from closing, or a valve not moving as freely as it should.
Such problems can often be solved very easily. The solution covers the following error symptoms:
- When a machine starts and stops without you pulling the trigger - i.e. in standby. Applies both when it is occasional AND when it starts and stops continuously
- When there is poor pressure, or occasionally poor pressure
- Whistling sound as a result of cavitation - i.e. a screeching sound when the pump stops
Place the machine on its back and remove the water hose. Spray CRC, WD40 or a similar lubricant oil into the water intake, so that the pump is well filled with lubricating fluid. Start up the motor using the main switch for a few seconds - and then turn it off again, so you can repeat this process one more time.
Let the oil do it's work..
Then connect the hose, set up the machine and flush through with the gun in bursts 10-15 times - without a nozzle
The "WD-40 trick" has been used since pressure washers first became available, and thus also works well with AVA machines. In this way, dirt that sits in places where it is an issue can be washed out, and sticky moving parts lubricated and the problem thereby often solved.
PS: A machine can also make noises if there is air in the pump, but then you would normally also notice noises or uneven operation during use. Air can be removed by just flushing through the machine a little with the gun without a nozzle, until you can see that the water jet is smooth and air-free.
Of course if the standby noise you are hearing is being caused by a visible leak (either a large and very obvious one, or something much smaller such as the connection between the gun and the hose), then the part in question must be repaired or replaced to stop water from escaping.