I've not found satisfactory schematics on line, so I took my unit apart. We didn't get spray out. Tested the lines for leaks (none), tested the pump (good pressure). Tried to flush the lines that go to/from the heater block in the upper (handle) portion of the unit. No flow. After much disassembly, we found that the heater core was blocked. Not wanting to buy a new one, we disassembled the core carefully and found the serpentine channels blocked. Scraped them clean -- carefully reassembled, and it works like a charm.
The gunk gumming up the heater core looked like solidified soap -- so I recommend flushing with cold water only throughly when done cleaning by turning off the heater core, turning the soap feed to straight water, and flushing good and long to cool the block and remove residue.
Leaving the heater on without flow (idling) is probably not healthy for this design.
Take apart: a philips head long neck screw driver and a flat-blade is all you need. Just take your time and do it one piece at a time. The bottom has about ten screws total, iirc. Wash every part before reassembly, careful not to tear up that rubber seal.
Put together carefully, too.
Your water line runs from the water tank to the soap mix valve, then to the pump. The pump appears to have a low pressure feed from one of the air snorkles to the top. The high pressure side of the pump feeds out to a T. This splits to the hand tool or up into the handle (heater). The feed back from the heater comes down to the spin indicator, and from there to a T to each of the two spray nozzles above the beater bar.
paul vail - afterhoursconsulting.org, October 2005
