390 and the detergent function doesn’t work

To engage the detergent tank on the 390, do the following:

  1. Attach the variable spray lance to the spray gun.
  2. The variable spray nozzle has two positions:
    a) The “Out” position activates low pressure detergent spray – grab the nozzle and pull it out/away from the spray gun.
    b) The “In” position activates high pressure water spray – pull the nozzle back toward the spray gun.
  3. The rotary detergent knob on the front of the unit adjusts the detergent mix ratio:
    a) 10:1 when knob is turned clockwise until it stops.
    b) 20:1 when knob is turned counter-clockwise until it stops.