Washing Machine Pressure Sensor Testing

Repair Clinic has already addressed how to test a washing machine pressure switch to help determine if the component is malfunctioning and causing a washer to overflow, stop mid-cycle, or not start at all. But not all washers use mechanical pressure switches. Many top-load and front-load models use an electronic pressure sensor to control how much water enters the tub for a wash or rinse cycle. This component is similar to the mechanical pressure switch but requires a different approach to testing to determine if the part is faulty. This article will examine what an electronic pressure sensor does and the unique way you can identify a broken pressure sensor.

What does a washing machine pressure sensor do?

An electronic pressure sensor communicates with the control board to regulate how much water will enter the tub for a wash or rinse cycle.

The pressure sensor can be a stand-alone component or part of the control board

Like a mechanical pressure switch, an electronic pressure sensor can be a stand-alone component attached to the inside of the appliance’s frame or located under the control panel. But on some washer models, the sensor will be part of the control board itself.

Top-load washer water usage vs. front-load washer water usage

Once the washer control or timer is set to the selected wash cycle and the start button is pressed, voltage is sent to the appliance’s water inlet valve, opening the valve, and allowing the appropriate amount of water to fill the tub. Typically, a top-load washer will use 8 to 18 gallons of water during a wash cycle whereas a front-load washer will use a more economical 2 to 5 gallons of water.

The pressure sensor will send a signal to the control board

One end of an air pressure tube is connected to the side or bottom of the tub while the other end is attached to the stand-alone pressure sensor or to the control board. As the tub fills with water, air pressure increases in the tube. When a sufficient amount of water has filled the tub, the pressure in the tube causes the electronic pressure sensor to send a signal to the control board which then shuts off the voltage to the inlet valve, closing it and stopping the water flow. The voltage is then directed to the washer’s drive motor or a rotor/stator assembly to start the wash and agitation cycle. A similar process occurs when the washer enters a rinse cycle.

A faulty pressure sensor can result in a water flow problem

The fill and rinse cycles are dependent on the pressure sensor and the attached air pressure tube operating properly. If the sensor is malfunctioning or the air pressure tube has a tear in it, too much water may be allowed to enter the tub, causing it to overflow.

If the air pressure tube is kinked or if there is a blockage in the tube, the washer may not fill or start at all. The same result can happen if the sensor fails to send an appropriate signal to the control board. An intermittently failing sensor may also be unable to detect that water has drained from the tub, resulting in the washing machine stopping mid-cycle.

Using a multimeter to test a washer pressure sensor

As we’ve established, if the washing machine is not filling sufficiently or is overflowing, the pressure sensor may be at fault. To help determine if the sensor is malfunctioning, you can use a multimeter to test for voltage changes in the sensor.

Start by unplugging the washing machine’s power cord

A stand-alone electronic pressure sensor will usually be attached to the inside of the washing machine’s frame under the main top or behind the console and will require the main top to be uninstalled to reach the sensor. If the sensor is part of the appliance’s control board, the control housing will normally need to be detached to access the board. Before you attempt any disassembly to reach the sensor, you should unplug the washing machine’s power cord to prevent electrical shock.

Inspect the air pressure tube

Before testing the sensor itself, inspect the air pressure tube for tears or kinks. If the air pressure tube is damaged, you may be able to replace just the tube depending on the model. To properly test an electronic pressure sensor, the washer will need to have power. So, once you’ve reached the sensor, plug the washer’s power cord back in, but be careful not to touch any electrical components with your bare hands.

The sensor operates using alternating current or direct current

You can tell if an electronic pressure sensor is malfunctioning by using a multimeter to measure the voltage changes in the component as the tub is filling with water. You will need to determine if the sensor operates using alternating current (AC) or direct current (DC) and set the multimeter’s selection dial accordingly. Next, use the washer’s wiring diagram to identify the pressure sensor’s input and output terminals or pins.

Start the washer to test the sensor

Select a wash cycle and press start. As the washer tub fills with water, the voltage coming out of the pressure sensor should change. Of course, if the washer is having a filling problem, you will need to pour water in manually to conduct the test. You should first check that voltage is reaching the sensor by contacting the black meter lead to the ground or neutral terminal or pin and the red meter lead to the power input terminal or pin. If no voltage is present, the control board is likely at fault.

Voltage will increase or decrease as the tub fills with water

If voltage is present, keep the black meter lead on the ground or neutral terminal or pin and contact the red lead to the power output terminal or pin. The meter display should show voltage increasing or decreasing as water fills the tub, matching the voltage levels indicated in the appliance’s water pressure sensor chart (you can find this chart in the owner’s manual). If the voltage changes as expected, the pressure sensor should be functioning normally and the washer problem could be caused by a defective water inlet valve or control board. However, if the voltage reading doesn’t change or there is no voltage present at the sensor output at all, you’ll know the sensor is faulty.

Watch our video, “Washing Machine Pressure Sensor Testing.”

Fix your washer with genuine OEM parts

When installing a new pressure sensor to fix your washer’s filling problem, or a new control board with the sensor attached, you should use a genuine OEM part for the best results. Repair Clinic stocks original manufacturer replacement parts compatible with the most popular top-load and front-load washer models, including those built by Whirlpool, LG, Samsung, Maytag, GE, Kenmore, Bosch, and Frigidaire. To find the right part for your model, enter the full model number of the washing machine in Repair Clinic’s search bar, then use the “Part Category” and “Part Title” navigation filters to identify the specific part needed for the repair.

More DIY repair help from Repair Clinic

In addition to stocking genuine manufacturer parts for appliances, outdoor power equipment, and heating and cooling products, Repair Clinic also provides unmatched DIY repair help. The Repair Clinic Content Library is filled with step-by-step guides, schematics, and procedural videos, such as this one showing how to install a new pressure sensor on a Frigidaire Laundry Center unit (Model FFLE3900UW1) or this one instructing you on how to replace an air chamber and air pressure tube on an Electrolux Front-Load Washer (Model EFLS627UTT). With Repair Clinic as your repair partner, you’ll always be in-the-know.

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