The electric Karcher pressure washers I have seen shut off when the trigger is released. To do this they must use a pressure sensor. When the trigger is not pulled the pressure builds up and trips the shut-off sensor. When the trigger is pulled the shut-off sensor detects the pressure drop and turns the pump on. That is a description of normal operation. The symptom you described is abnormal and makes me think the shut-off sensor is detecting a pressure drop like a leaky trigger or a leak back through the pump, hose, or somewhere else or perhaps a defective pressure sensor. Not a big deal. Just don't leave the pressure washer turned on very long when you are not using it.

Thanks for that.
Have been doing as suggested and simply turning it off when not using. Any ideas how to access the pressure sensor and how difficult/costly it would be to replace?
Cheers,
Jack

I don't own one and I can't help you on the location of the sensor. Maybe your owner's manual has a parts diagram or perhaps Karcher has some online parts information???

Cheers

Thank you for your assistance.

Jack

These people can help you if you click on the link I posted

Here is a link that might be useful: Parts Store

Hello,

Your pump head (plastic) may have a hairline crack in it, or an internal check valve is not seating. This problem can be fixed with parts. You can download Karcher parts lists and owners manuals at the link below. You can also call our Karcher Tech Support Hot Line at 800-999-2245.

Here is a link that might be useful: Karcher Parts & Owners Manuals