Jack,
This YOUTUBE may help point the way?
How to Diagnose Pressure Washer Electrical Problems
Also it appears that your K5 has a GFI? WITH THE POWER DISCONNECTED:
Can you jumper ACROSS the GFI and CAREFULLY see if your K5 powers up?
While I found plenty of parts lists, I found no schematics! Darn.
Anthony
This video maybe helps you. Try to watch the video very carefully. Otherwise, you have to buy a new pressure washer surface cleaner. Before buying a new surface cleaner plz read buying guide of pressure washer surface cleaner