Poor foam quality
Suction filter at the end of the suction hose is blocked by chemical residues
The used chemical product is not a foam product
Air pressure too low
Air valve not opened or compressor not started
Chemical product is mixed with water
Chemical restrictor does not match the chosen detergent type.
Incorrect foam nozzle is being used
No - or too short - outlet hose is used
The function selector switch is not turned to "foam"