Solution and Pump Faults: Solenoid Valves, Pumps, Dosing and Level Sensors
Scrubber solution, solenoid valve, pump and detergent fault codes explained: what the controller detects, ranked causes, coil and current tests, and fixes.
Key takeaways
- Most solution faults are open circuit or overcurrent on a small output such as a solenoid valve or pump.
- The most common cause of no solution is still a clogged filter or empty tank, which never throws a code.
- Check coil resistance and voltage at the connector before replacing a valve or pump.
- Dosing pump faults are often caused by an empty, kinked or crystallized chemical line.
- Empty solution warnings rely on a level sensor that can be fooled by scale or foam.
A solution or pump fault code means the controller detected a problem in a solution output, typically the solenoid valve, an electric solution pump, a detergent dosing pump, or a tank level sensor. In electrical terms it is usually an open circuit (nothing connected or a broken coil), an overcurrent or short, or a level sensor reporting an empty tank.
Keep in mind that the most common cause of "no water on the floor" is not electrical at all: a clogged solution filter, a kinked hose, or an empty tank. The controller cannot see a blocked filter, so a machine can have zero flow and no code. If you have no code, start with no solution flow. If you do have a code, this page explains what it is pointing at.
What the controller is detecting
Solution systems vary: gravity-fed machines use a solenoid valve; pump-fed machines use a small diaphragm pump plus a valve or pulsed pump control; machines with on-board chemical use a separate dosing pump. Each of these is a low-current output compared with the brush and vacuum, often a few amps or less.
| Component | Typical fault types | What it means |
|---|---|---|
| Solution solenoid valve | Open coil, shorted coil, output fault | Valve not connected or coil failed; driver in controller may be damaged |
| Solution pump | Open circuit, overcurrent, stall | Pump unplugged, motor failed, or pump blocked or running dry against a restriction |
| Detergent dosing pump | Open, overcurrent, empty chemical | Pump disconnected or seized, chemical container empty or line blocked |
| Solution level sensor | Tank empty, sensor fault | Tank actually empty, or sensor fouled or disconnected |
| Water treatment or electrolysis module (some chemical-free systems) | Module fault, low conductivity, scale | Module failure or water quality outside range |
Machines with chemical-free or electrically converted water systems may report faults specific to that module. Those systems vary greatly by maker, so rely on the manual. For background, see chemical-free scrubbing.
Typical display wording
Look for messages referring to solution valve, solenoid fault, solution pump, pump overcurrent, detergent pump, chemical empty, solution tank empty, or solution system fault. Some displays show a solution flow indicator that flashes rather than a code. As always, confirm the exact meaning in the manual for your serial range.
Common triggers, ranked by likelihood
- Solution tank empty or level sensor reading empty because of scale or debris.
- Connector unplugged or corroded at the valve or pump, often after tank removal or washing the machine.
- Solenoid coil failed open, commonly after years of heat cycling or water ingress at the connector.
- Pump seized or worn, often from running dry or from debris passing a missing filter.
- Dosing system: chemical container empty, line kinked, or chemical crystallized in the line or check valve.
- Shorted coil or wiring, producing an overcurrent fault and sometimes a blown fuse.
- Controller output driver failed, usually after a shorted coil.
Step-by-step diagnosis
Safety: key off before unplugging components. Have a towel ready; solution lines hold water.
- Confirm the basics. Tank filled above the minimum mark, flow setting not at zero, solution switch on, brush deck lowered (many machines only open the valve when the brush is running).
- Clean the solution filter and check hoses for kinks. See solution solenoid and filters.
- Listen for the valve or pump. A solenoid valve clicks when energized; a pump hums or pulses. No sound points to electrical supply or the component itself.
- Measure voltage at the connector. Key on, solution commanded on, back-probe the valve or pump connector. You should see close to battery voltage, or a pulsed voltage on machines that control flow by pulsing (a standard meter may show an average lower than battery voltage). No voltage points to wiring or the controller output.
- Measure coil resistance. Unplug the valve. A healthy coil on a 24 V valve typically reads in the tens of ohms; compare to the manual or a known good valve. OL means an open coil; a reading near zero means a shorted coil.
- Measure pump current with a DC clamp meter if you suspect overcurrent. Compare to the rated value. High current with free flow suggests a failing pump motor; high current only with outlet restricted suggests a blockage downstream.
- Check the level sensor. Clean it. Then use the service menu input test or a meter to confirm its output changes when the tank is filled and drained.
- Dosing system: confirm chemical is present, prime the line per the manual, inspect the check valve for crystals, and check pump voltage and current as above. See chemical dosing systems.
Fixes
| Finding | Fix |
|---|---|
| Empty tank or fouled level sensor | Refill; clean sensor; descale if hard water deposits |
| No voltage at connector | Repair wiring or connector; check fuse; check controller output |
| Coil open or shorted | Replace valve coil or valve assembly |
| Pump seized or high current | Replace pump; fit or replace the strainer upstream |
| Dosing line blocked | Flush with warm water, replace check valve, prime line |
| Controller output dead after a short | Replace the shorted component first, then the controller or its output |
Getting the flow rate right after a repair matters as much as getting it working; see solution flow settings and tanks and solution flow.
Reset behavior
Tank-empty messages clear once the tank is filled and the sensor sees water. Open circuit faults on valves and pumps often re-check every time the output is commanded, so they clear by themselves once the connection is restored. Overcurrent faults on outputs usually latch until key cycle, because the controller has shut the output to protect its driver. Dosing faults may need a prime cycle from the menu after the container is replaced.
Fault record worksheet
- Exact code or message and when it appears (at deck lowering, mid-run, at startup)
- Hour meter reading
- Solution tank level and whether the level indicator agreed
- Flow setting and whether the brush deck was down
- Filter condition when checked
- Voltage at valve or pump connector with solution commanded on
- Valve coil resistance
- Pump current, if measured
- For dosing systems: chemical level, dilution setting, and when the line was last primed
- Water hardness or scale observed (for sensors and chemical-free modules)
To check the chemistry side after flow is restored, the dilution calculator converts ratios to ounces per gallon for a full tank.
Frequently asked questions
Why is my scrubber not putting down water even with no error code?
The controller cannot detect a clogged filter, a kinked hose or a valve stuck by debris, so these cause no flow without any code. Clean the solution filter and check hoses first.
How do I test a scrubber solenoid valve?
Unplug it and measure coil resistance with a multimeter: an open reading or near zero means the coil has failed. Then, with power on and solution commanded, check for battery voltage at the connector and listen for the click.
What does a solution pump overcurrent fault mean?
The pump drew more current than the controller allows, usually because the pump is seized or worn, running against a blockage, or has a shorted motor or wire. Check current with a DC clamp meter and inspect the line downstream.
Why does my scrubber say solution tank empty when it is full?
The level sensor may be coated with scale, debris or chemical residue, or its connector may be loose. Clean the sensor, check the connection, and use the service menu input test if available.
Why does my machine only dispense solution when the brush is down?
Most scrubbers interlock the solution output with the brush so water is not dumped on the floor while transporting. This is normal design, not a fault.