Using a L-21N level switch in carpet cleaner tanks is a great way to have level control. Keeping up on maintenance and inspecting hoses will help prolong the life of the level switch and the carpet cleaner. Having a kinked hose on the carpet cleaner could create a surge on the motor generating an over amperage spike. The spike of over amperage will affect the level switches micro switch operation. When the level switch receives too much amperage the contacts on the micro switch get hot and melt the plastic plunger on the micro switch during switching, creating either a constant open or closed circuit. To tell if the micro switch is bad the plastic plunger under the actuating arm will be depressed and not fully rebounding. The micro switch is a replaceable component of the level switch that is easily replaced.