A level sensor or pressure switch is a small device that controls the volume of water poured into the tank. Without it, the washing machine system will not start drawing, will not receive a signal to start the wash, and will not turn on rinsing or draining. In order not to find yourself in an unpleasant situation in front of a non-working machine, it is better to deal with the miniature but important device in advance. We will discuss its appearance, internal structure, principle of operation, possible breakdowns and testing methods in detail in this article.
What does the sensor look like?
Finding the pressure switch is easy: just unscrew the top panel of the washing machine and look around. You need to find a small plastic element with a round lid - this is exactly what this part looks like. Several conductors from the control board and one long tube going downwards approach it. A special pressure tank is also connected. The operating principle of the sensor can be described as follows.
Liquid entering the washing machine causes pressure to build up in the pipe.
As soon as the equation of water and pressure occurs, the switch closes and the contacts open.
The control triac receives a signal indicating sufficient intake.
If the pressure switch fails, the system is not informed about the amount of water filled. The result is underfilling or overfilling. Due to the lack of information about the degree of filling of the tank, the machine often insures itself and activates the pump to remove excess in order to avoid leakage. Before it gets into the tank, all the liquid from the water supply is immediately drained into the sewer.
This continues until the owner of the washing machine stops the liquid intake and eliminates the cause of the problem.
Sensor device
Now let's figure out how the pressure switch works. The main part of the sensor is a plastic housing that holds the main structural elements. Among them:
inlet fitting;
membrane with push-on tip;
two parallel contacts;
sensitivity adjustment screw;
level screw;
thrust elements fixing two springs.
Variations are not excluded. Thus, electronic pressure switches have an oscillatory circuit. In two-chamber ones, in addition to the lower hollow compartment, there is a second one on top, as well as an additional intermediate membrane and a pair of contacts.
Typical level sensor failures
Knowing what a level sensor is and what it is responsible for, it is easier to suspect something is wrong at the earliest stages. Then you can fix the problem quickly and at minimal cost. So, you can guess about a failure based on several symptoms.
The cycle started with an empty drum. The system did not receive a signal about an empty tank and started washing. It’s worse if the heating element also turns on. This will inevitably lead to burnout of the heating element and the supplied wiring, which are not intended for idle operation.
Water intake does not stop or stops immediately. The first option is worse, since uncontrolled filling of the tank is fraught with leaks and short circuits.
Draining is difficult. Giving a signal about the need to drain is another point for which a pressure switch is needed. If a failure occurs, then after the spin is completed the cycle stops with a full tank and the hatch door locked.
No rinsing. The water cannot be changed to clean water, since neither the drain nor the fill works.
Modern washing machines are able to diagnose the problem independently and display the corresponding error on the digital display. In older models, the situation is more complicated - the sensor must be constantly checked for functionality in order to promptly detect a problem that has occurred. The verification algorithm is described below.
How to check a part?
Before blaming the water level sensor for the stalled operation of the washing machine, you should confirm or refute your guess. To do this, it is enough to check its functionality using a simple algorithm. We proceed like this:
disconnect the washing machine from the power supply;
turn off the water;
remove the top panel from the machine by unscrewing two screws from the back and sliding the cover towards you;
determine the location of the sensor (most often it is located in the upper part of the side wall);
we find a tube with a diameter equal to the inlet fitting;
loosen the clamp on the pressure hose and unhook it;
insert the prepared tube into it and blow lightly.
If you hear 1-3 clicks, it means the contacts are working smoothly. Next, carefully inspect the housing and all adjacent wires for damage and blockages. The final stage of testing will be connecting a multimeter. We set up the device to measure resistance and apply the probes to the terminals on the pressure switch. Everything is fine if the values on the display change, otherwise we dismantle the part and install a new one.
Important! In some cases, you can adjust the pressure switch by tightening the screws, but only service technicians do this.
Most often, a damaged sensor cannot be repaired. All that remains is to unscrew the screws holding the housing, cut off the clamps and disconnect all the pipes with contacts.Then purchase a similar copy and install it in the washing machine in place of the previous one.
A level sensor or pressure switch is a small device that controls the volume of water poured into the tank. Without it, the washing machine system will not start drawing, will not receive a signal to start the wash, and will not turn on rinsing or draining. In order not to find yourself in an unpleasant situation in front of a non-working machine, it is better to deal with the miniature but important device in advance. We will discuss its appearance, internal structure, principle of operation, possible breakdowns and testing methods in detail in this article.
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