The water sensor in the dishwasher: types, device, how to check + repair

Evgenia Kravchenko
Checked by a specialist: Evgenia Kravchenko
Author: Victor Kitaev
Last update: May 2019

Household dishwashers deservedly received the status of an integral part of the kitchen equipment. They really show high performance. But like any other type of household appliances, dishwashers tend to fail from time to time.

A common cause of inoperability is the water sensor in the dishwasher, also called the pressure switch. We will talk about the technical symptoms that can identify a malfunction. Let’s show you what kind of damage you can fix yourself, and which one is better to contact a service workshop.

Pressostat function in the washer

A feature of the design of the dishwashing machine is the use of the optimal amount of water with high cleaning efficiency.

Actually, this factor is an obvious point, since the degree of cleaning of kitchen utensils by dishwashers depends not so much on the amount of water, but on its temperature and spraying technology.

Dishwasher Repair
The functionality of dishwashers has its own design features, due to which a relatively large volume of water is used to wash a fairly large set of kitchen utensils

On the contrary, if the unit uses too much water, due to the increased hydraulic resistance, the spray function is disrupted, and heating will require a lot of power and time.

That is why an important component dishwasher designs is a water level sensor. The presence of this device allows you to control and maintain the exact water level in the machine.

Dishwasher filter clogged
The quality of the washing process is largely dependent on the quality of the incoming water. If it contains a high percentage of suspended solids, quick wear of various structural parts is guaranteed

Meanwhile, the correct and faultless operation of the machine is noted, as a rule, in the initial period of operation of the equipment.

Then, at some point in the use of the equipment, the owner of the dishwasher begins to notice a malfunction in her work. The root cause of failures is usually the pressure switch. And the point here is not at all in its quality.

Dishwasher pressure switch
One possible design for the pressostat of a dishwashing machine. Completely plastic case and only contact group of the switch and several fixing screws - metal

A significant role in this process is played by the quality of the water used to power the dishwasher. Unfortunately, in most cases of operation, there is no need to talk about the high quality of water from a centralized water supply system.

And low-quality tap water pretty quickly disables plumbing of any kind. Pressure switches of the washing machines are proof of this.

Varieties of sensors for dishwashers

The level sensors used in the constructions of dishwashers can conditionally be divided into two groups: mechanical and electronic.

The principle of operation of the pressostat

The device (sensor) of mechanical action works on the principle of transferring water pressure to a silicone membrane. The pressure force from the membrane is transmitted through the rod to a contact device (usually a relay).

The action of this force mechanically closes or opens the contacts of the control device, which in turn acts on the water supply element.

Mechanical level sensor
The diagram showing the operation of the water level sensor on the example of one of the models of Bosch machines. Level control is carried out in two levels (B and A). Lock-up or switch-on device - simple end microswitch connected to the pressure switch piston

The cause of the malfunction of the mechanical action system, as a rule, is a silicone membrane - more precisely, its physical damage in the form of a breakdown of the surface.

Accordingly, in this state, this element stops working - to perceive pressure. As a result, the user receives a violation of the water level inside the bathtub of the dishwasher.

Mechanical sensor circuit
Another version of the pressure switch with the ability to adjust the pressure of water on the membrane. As a rule, it was used in old-style models. However, the new systems use similar designs, slightly modernized

Electronic type sensors work in much the same way. Only in this case relay components are not used. Instead of relays, the functions of switching modes (operating, emergency) are performed by semiconductor components.

Additional features are inherent in electronic devices - automatic detection of malfunctions and the display of error messages directly on the display of the machine.

Errors on the display of the dishwasher
An integral part of electronic type control. With electronic control of the pressostat, errors that occur during operation are displayed. From the values ​​given, it is quite simple to determine whether the water level sensor is faulty

It is clear that the diagnosis of a malfunction in the presence of an electronic device is greatly facilitated. According to the error code on the display, the owner can first understand for himself what needs to be done in terms of repair.

However, repairing electronic systems is more difficult than mechanical ones. Therefore, here most likely you can’t do it yourself. Professional intervention required.

Element Design

The design of the sensor allows the most unusual circuit. For example, in some cars of a famous brand Electrolux The pressostat module is based on two individual sensors.

One of a pair of such devices controls a low water level, and the other, respectively, is high. Therefore, it is not always possible to do with simplified dismantling during repair.

The water sensor in the dishwasher: types, device, how to check + repair
Often there is such an option as the inaccessible location of the sensor in the designs of many models produced under the brand name Electrolux, Bosch and others.In such cases, to get to the pressostat module, which performs the function of monitoring the water level, you have to disassemble the dishwasher

And in another case - when, for example, on a budget models of the brand Bosch there is only one sensor that monitors the total water level. In this embodiment, disassembly is accompanied by less difficulties, but there are difficulties with access to it on the chassis of the machine.

That is why it is far from always possible to replace faulty sensors on their own. More often it is required to attract a master from a specialized service workshop.

Professional repair service
Sometimes to access the sensors you have to disassemble the dishwasher almost completely. In such cases, the best option is to contact a professional service for help.

Meanwhile, in a dishwasher from Electrolux, where two sensors are involved, a device that monitors a high level is used as a duplicate control element.

If during operation of the device the low level control sensor does not work, then when the water reaches the upper limit, the drain pump is turned on. The signal for this is supplied by the upper control device.

Dismantled pressure switch and pan
Something like this might look like a machine that had to be disassembled just to replace the level sensor or just its membrane. The process requires skills and careful work.

The main function of tracking the volume of water is assigned to the sensor, designed to control the lower level. This appliance is activated at the initial stage when the process of filling the dishwasher with working fluid starts.

The nuances of checking the health of the sensor

The sensor switch is connected to the device itself and as soon as the tank, called the bathtub, is filled at the set lower limit, the pressure switch membrane acts on the rod, which moves the switch contacts under pressure.

Pressostat Check
Having reached the desired part - the pressostat, you can try, without turning off the element, ring its contact group with a tester. However, if the membrane is faulty, you will have to remove and disassemble the module one way or another

If there is a possible malfunction at this point, you can verify for sure by checking the lower level relay.

To do this, the following actions are performed:

  1. Removes the power of the dishwasher.
  2. The control panel service panel is opened.
  3. The circuit determines the relay conductors.
  4. The device measures the resistance between them.
  5. Without water in the pan of the machine, the tester should not show contact.
  6. If there is contact with flooded water, then the relay is working properly.

In a similar way, the health of the upper level monitoring relay is checked. Checking is also carried out through the control panel using the machine concept.

It is necessary to identify the conductors and contact plaques on the board coming from the switch of the upper level relay and ring them when the pallet is empty and filled.

Replacement Instructions

Repair as such for pressostat membranes seems to be useless, almost impossible. As a rule, such elements of the device must be replaced.

But before changing the membrane, you will have to determine the exact model of the level sensor used. For the dishwasher of each individual brand, these details differ significantly.

Electrolux Level Sensor
Water level sensor, which can be found in the construction of dishwashing units manufactured under the Electrolux brand. This is a single device, familiar to mid-range cars

That is, in any case, the user or service representative will need to disassemble the dishwasher in order to be able to get to the defective part and determine its brand. We will figure out how to perform this operation if it is decided to do the work yourself.

Again, with respect to a specific model of dishwashing equipment, the disassembly sequence may vary.

Consider, for example, the option with a dishwasher from Bosch, which uses the mechanical design of the level sensor:

  1. Disconnect the device from the network and plumbing communications.
  2. Prepare free space for work.
  3. At the prepared site, install the machine upside down.
  4. Unscrew the screws holding the bottom case cover.
  5. Remove the cover and find the pressure switch according to the documentation.
  6. To dismantle the device, having previously disconnected all components from it.

After dismantling the sensor, free access to relay elements and mechanical parts will open. To check and, if necessary, replace the membrane, you will need to disassemble the pressure switch housing. Usually, two halves of the case are fastened with two or three screws, but structures with plastic latches are more common.

Bosch Level Sensor
Several advanced pressure switches for Bosch dishwashers. In fact, it is a non-separable part, which should only be changed during breakdown. True, some master craftsmen restore such instances.

You should also check the operation of relay elements. Bosch dishwashing machines typically have limit switches. Checking their integrity is easy.

To do this, use a measuring device, which is connected alternately to the switch terminals and manually act on the push-button mechanism. During normal operation of the switch, one of the terminal groups must be shorted.

If there is no short circuit and a characteristic click is not heard, the switch is most likely faulty. In this case, this part must be replaced. You should also resort to replacement if there is an unstable (unstable) contact between the terminals.

Useful Repair Tips

Each dishwasher model has its own characteristics. Therefore, if you decide to do it yourself, you are advised to fix the sequence of actions, for example, by writing on a piece of paper. Before work, it is advisable to carefully study the instructions and familiarize yourself with dishwasherlocated in the passport.

Dishwasher design
A full set of dishwasher parts that one way or another will have to face if there is an issue with repair / replacement of the water level sensor. Therefore, before performing work, it is recommended to carefully study the design of the unit

All dismantled parts must be laid out in the strict order of removal; for screws it is better to prepare some kind of small dishes or box. If these rules are observed during disassembly / assembly, unnecessary problems can be avoided. And assembly after replacing parts with such a solution is much easier to perform.

Assembly is carried out strictly in reverse order. Care and ease of action is required. Many parts of household appliances are often attached with plastic clips, which are easy to break off during rough installation. After completing the assembly, check the dishwasher for proper operation.

So that your favorite unit of household appliances does not create problems and does not cause a headache, first of all, you must observe dishwasher rules. In this case, the working life of important technical parts and components will increase significantly, and the owners will not need to look for spare parts for replacement.

Conclusions and useful video on the topic

The video is close to the topic where the author in an intelligible form tells and shows almost everything that he knows about pressure switches - water level sensors used in the design of dishwasher units:

Video on how to repair a dishwasher with your own hands:

Having become acquainted with the device of the sensor and the procedure for carrying out work in case of its breakdown, you can try to repair it yourself. But almost all modern equipment is produced without taking into account possible repairs, and more often the broken part has to be changed completely.

Often, repairs cost costs that are comparable to the price of a new similar model. Therefore, a more reasonable option is to provide the machine with proper operating conditions, which will ultimately lead to long-term trouble-free operation.

Want to talk about how you picked up a water sensor for replacement in a dishwasher? Do you have useful information on the topic of the article? Please write comments in the block below, ask questions, share photos and useful information.

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