A dishwasher that hums but does not fill with water is usually caused by either a defective water inlet valve or float switch. If your dishwasher’s water inlet fill line features a flood-safe hose, this may also cause the problem. If the dishwasher has not been used for over a week, this can also cause the issue, as the dishwasher pump seals may have dried out.
The first thing to check is that the water supply is turned on to the dishwasher. Most households have a faucet under the sink that needs to be turned counterclockwise to allow water to flow into the dishwasher. If you live in a cold climate, another consideration is that the water supply line may have frozen.
1. Defective Water Inlet Valve
When the control panel or timer signals the water inlet valve, it should open and allow water into the dishwasher. If the water inlet valve is defective, the dishwasher could still be humming but not getting the water it needs. A defective water inlet valve may also cause a loud buzzing or squealing sound.
To inspect and replace the water inlet valve, the bottom access panel or kickplate will need to be removed. On some dishwashers, you may need to remove the dishwasher door, usually with a T15 Torx Driver, to gain access.
A defective water inlet valve can be visually inspected for signs of wear and tear. An ohm test can also be conducted with a multimeter. If the test measures infinity, one of the solenoids may have failed. However, this multimeter test is often unreliable. To correctly test the water inlet valve, a more advanced AC or DC voltage test is required. It is recommended that a trained professional perform this test.
To check and replace the water inlet valve, see the instructions below.
2. Clogged Water Inlet Valve
The water inlet valve can become clogged, usually due to calcium deposits. If your water supply has a known hard water issue, it is more likely that this is the cause of the issue. A clogged water inlet valve can be diagnosed and fixed by locating the filter screens inside the water inlet valve’s hose fitting ports.
If the water inlet valve screens are clogged, you may be able to wipe or scrape the debris off the screens or remove the screens and clean them. The screens can also be soaked in a water and vinegar solution to decalcify them. However, water inlet valves are usually cheap to replace, and repairs to a water inlet valve often result in it leaking and causing more problems. Therefore, replacing the valve is usually the better option.
To check and replace the water inlet valve:
- Disconnect the dishwasher from the power source.
- Turn off the water supply to the dishwasher.
- Remove the lower access panel or kickplate.
- Put a towel down to catch any water leakage.
- Remove the water supply line from the inlet valve assembly.
- Remove the mounting screw and pull the water inlet valve from the mounting bracket.
- Disconnect the water inlet valve wiring harness by releasing the locking tab.
- Release the wire clamp on the water inlet tube, and pull the inlet tube off the water inlet valve.
- Remove the water inlet valve from the dishwasher.
- Inspect the water inlet valve for signs of damage and clogged filter screens. Clean the screens if required.
- Perform a multimeter or voltage test.
- Replace the water inlet valve if required.
3. Malfunctioning Float
The float is located at the bottom of the dishwasher tub. The float moves up and down in relation to the water level and is a safety device to prevent the dishwasher from overflowing. If the float is not working correctly, it could be responsible for the dishwasher humming and not filling with water.
To check the float:
- Locate the float at the bottom of the dishwasher’s tub. The float usually has a circular head, and the float cover may need to be unscrewed to access it.
- Determine if the float can move up and down. When you move the float, you should hear the relay switch click. If it doesn’t click, the float assembly will most likely need to be replaced.
- Check and replace the float and float switch by following the instructions below.
4. Defective Float Switch
The float switch tells the water inlet valve to either stop or allow water into the dishwasher. If the float is working and the water inlet valve is not responsible, the float switch is likely to be responsible for the dishwasher humming but not filling with water.
To check and replace the float switch:
- Disconnect the power to the dishwasher.
- Turn off the water supply to the dishwasher.
- Remove the bottom access panel or kickplate. Some dishwashers may require the removal of the dishwasher door, usually with a T15 Torx Driver, to gain access.
- Locate the float switch beneath the float.
- Unplug the wiring harness from the connector. Be careful not to pull directly on the wires when removing the wiring harness.
- Remove the float switch and test it with a multimeter.
- Set the multimeter to Rx1 and touch the probes to the switch’s terminals. The multimeter should either read zero or infinity.
- With the probes still touching the terminals, press the switch’s button. This should change the reading to the opposite extreme (from zero to infinity or infinity to zero). If the reading does not change, the float switch should be replaced.
5. Dry or Stuck Pump Seals
If the dishwasher has not been used in a while, the dishwasher pump seals can dry out and stick, which can cause the dishwasher to make noise but not fill with water.
To fix the problem:
- Empty the dishwasher.
- Remove any water that is in the dishwasher tub.
- Dissolve three to four ounces of citric acid in one quart of hot tap water. White vinegar can also be used, but it is not as effective as citric acid.
- Pour the citric acid solution into the sump area, and let it stand for fifteen to thirty minutes.
- Run a test cycle to see if the issue has been resolved.
6. Water Inlet Fill Hose
Some dishwashers have a check valve in the water inlet fill hose that can occasionally fail and stop water from coming into the dishwasher. If the above solutions have not solved the issue, you may need to contact a trained professional to diagnose and replace the water inlet fill hose.