Pressure washer problem

Another John pretended :

A bit of a guess here...

The idea is that if you release the trigger, the pressure builds up and switches the pump off. So either the pressure is leaking away, or the pressure switch might be set to high.

The leak could be via the one way valve between pump and hose, including where the pressure switch is located. In the hose, its connections, or the lance before the trigger.

Make sure you disconnect power and release pressure via the trigger, before messing with it - they store some serious pressure.

Another John :

When my Karcher started doing that it was a slight leak on the high pressure side (split plastic moulding). When the pressure drops below a certain level, the motor starts, gets up to full pressure, stops, then the pressure starts dropping again.

Mine does the same, different make though. I just turn the unit off between uses not worth farting around with really.

It could be the pressure switch, but more likely a small leak on the high pressure side will cause exactly this fault.

Check the 'o' rings where the hose leaves the machine, joins the gun etc.

If it is the pressure switch it just needs a 'tiny' adjustment.

My Karcher has done that since it was brand new - I assumed it was normal!

Indeed - a new set from ebay fixed this feature on mine...

I have noticed that you can get this behaviour if you don't purge all the air from it first before powering up - so let water run through it until it is coming out of the lance without any interruptions or "clicks" as air is ejected.

Best way to start any pressure washer;

Connect to tap. Remove lance, open gun, allow water to clear air. With gun still open & no lance, switch on. When you have a nice even flow, fit lance & carry on.

OP here: *Brilliant*!

A classic example of the way this group works: thanks very much for all the instant responses, chaps. I will pursue the various possibilities. It's like being lost, and then a helpful passer-by giving you a map!

Thanks again John