Overview
Waste tank float switch assembly, Harwil. Sapphire part number 69-000S, listed in the parts schedule as Assy, Level Sensor Shutoff / Warning / Float Switch.
Compatible with Prochem, HydraMaster and Sapphire truckmounts.
What it does
A float suspended inside the waste tank rises and falls with the water level. At a set height the switch changes state, and depending on how the machine is wired that either:
- controls the automatic pump-out, turning the APO pump on and off, or
- shuts the machine down in a high-waste cut-off application, to stop wastewater reaching the blower.
The second job is the important one. A blower that ingests wastewater is a repair that takes a machine off the road, and this inexpensive switch is what stands between the tank and the blower.
Diagnosing it
Float switches fail in two ways and they look completely different from the driver's seat:
- Stuck low (reads empty when full) — the machine never sees the tank fill. This is the dangerous one, because everything appears normal until slurry reaches the blower.
- Stuck high (reads full when empty) — the machine shuts down or runs the pump-out when it should not. Annoying, and it fails safe.
Before you condemn the switch, clean the float. Fibre, hair and slurry wrap around a float in a waste tank and restrict its travel, which produces exactly the same symptoms as a dead switch and costs nothing to fix. Check the connections next — a wet tank environment is hard on terminations.
Test it deliberately rather than waiting to find out. Lifting the float by hand with the machine running should produce the response the machine is wired for. That takes a minute and it is worth doing at every service.
Fitting advice
Note the orientation and the mounting height before you remove the old switch. A float switch fitted at the wrong height changes the level at which the machine acts, which on a shutdown application is the whole point of it.
Seal the mounting properly and check the wiring is routed clear of the tank contents.
If the machine has a splash guard or protector around the float, fit it. It is there to keep debris off the float so the float can travel.
Frequently asked questions
Which machines does it suit?
Prochem, HydraMaster and Sapphire truckmounts, per CCW's record. Send us your model and we will confirm the mounting.
Is it the pump-out switch or the shutdown switch?
It can be either — that depends on how your machine is wired. Tell us which function you are replacing.
My machine reports full with an empty tank. Is the switch dead?
Clean the float first, then check the connections. Both are more common than switch failure.
What are the electrical ratings?
Not stated in the documentation we hold. Ask us if you need the specification.
Tell us the machine and what the switch is doing and we will help you sort a fouled float from a failed switch before you order.
