The PMM heating element fails quite often. This is due to the low quality of tap water in most Russian regions. On modern Bosch dishwashers, heating elements “live” for about two to three years, then repair or replacement of the part is required.
Let's figure out how to repair the heating element of a Bosch dishwasher. Will an ordinary user be able to do this kind of work, or is it better to contact a service center? Maybe it would be easier to install a new heater? Let's look into the nuances.
We disassemble the machine and remove the heating element
It’s easier to buy and install a new heater on a Bosch dishwasher. However, the price of the issue will be quite high. Therefore, many users, wanting to save money, decide to repair the heating element of the dishwasher.
The heating element in modern Bosch dishwashers is enclosed in the same housing with a recirculation pump.
To get to the heater, you will need to remove the recirculation pump from the dishwasher. During the dismantling of the heating element, you will have to almost completely disassemble the PMM housing. You need to have the following tools on hand:
TORX T20 screwdriver;
TORX T15 star screwdriver;
wrench 17;
Phillips screwdriver;
pliers;
soldering iron
With your tools ready, you can begin disassembling your Bosch dishwasher. First, turn off the power to the device by unplugging the power cord from the outlet. Further:
disconnect the machine from communications (water supply and sewerage);
open the PMM door, remove all the dish baskets from it;
unscrew the bolts that secure the dishwasher to the kitchen unit (they are located on the side walls of the washing chamber);
close the dishwasher door;
remove the lower false panel of the furniture set;
Using a 17 mm wrench, twist the legs of the PMM so that the body of the machine goes down;
remove the car from the furniture;
Unscrew the garbage filter located at the bottom of the dishwasher bin;
remove the filter unit, blot the water in the opened hole with a dry cloth;
remove the decorative trim of the door opening mechanism;
remove the screws securing the PMM side trim panel and move it to the side;
pull the tensioner ropes for opening the machine door and remove them from the mechanism;
turn the dishwasher around on the other side, also remove the false panel and tensioners;
turn the machine upside down;
unscrew the two screws securing the lower false panel of the PMM, located at the front of the case, remove the part;
using pliers, loosen the clamp on the filler pipe and disconnect the hose;
unhook the drain and inlet hose mounting panel from the body;
disconnect the Aquastop connector;
at the bottom of the PMM, unhook the float end of the Aquastop system;
remove the lower part of the PMM body, having mastered the latches;
loosen the water and sewer hoses;
disconnect the contacts from the circulation pump;
unhook all pipes from the pump;
remove the circulation pump.
During the work, it is advisable to take photographs that will help you avoid mistakes during reassembly. The recirculation pump is well “hidden”, so the process of dismantling it is quite labor-intensive. If you understand that you cannot cope even with this stage, it is better to seek help from a specialist.
Disassembling the circulation pump and checking the heating element
You can understand that the heating element of the dishwasher is out of order based on several signs. Firstly, the machine will not wash dishes well.Secondly, it will not dry cutlery. If such “symptoms” are observed, it is worth checking the heater.
The failure of the heating element is also indicated by error E1 (depending on the Bosch PMM model, code E01, F1, F01 may be displayed).
So, now the pump is ready for diagnostics. The recirculation pump of Bosch dishwashers consists of two parts, connected around the perimeter with latches. One of them has a heating element. Further work will take place with this half of the structure.
The next step is checking the heating element. The heating element is tested using a multimeter. The device must be switched to resistance measurement mode.
Next, the resistance produced by the heater is measured. The multimeter probes are applied alternately to different terminals. Considering that the power of the heating element is approximately 2 kW, the resistive resistance between the supply contacts should be about 24 Ohms.
There should be no resistance between ground and any power supply.
When there is no resistance between the supply contacts, we can talk about a break. Inspect the traces of the heating element next to the terminal block. Perhaps one of them has burned out; this will be visible to the naked eye.
During the repair, it will be enough to solder the track. However, everything is not so simple - the soldering area is hidden by protective casings of the heating element: plastic and metal. Therefore it will be necessary:
Using a metal drill, 3.5 mm in diameter, remove the rivets on the steel casing;
release the heating element from the metal casing.
The figure below shows the complete composition of one part of the circulation pump:
The heater is a ring element with several tracks. Further work will take place with him.To restore the heating element's functionality, you will need to solder it. You can do this yourself. We'll tell you how to repair an element.
Soldering the heating element
The idea of repairing the heater is to free its tracks from the insulating layer and solder a new conductor there, restoring contact. To do this you will need sandpaper. With its help, part of the top coating of the heating element is carefully erased.
For ease of work, it is recommended to wrap a ruler in sandpaper. It is better to use paper one step higher rather than zero. After this, proceed to remove the top insulating layer from the track.
Removing the insulation from the heater tracks is quite difficult. The work may require effort and take 10-15 minutes of time. Having cleared the place, you can move on.
After the insulating layer is removed from the contact track, it is necessary to fill it with solder to restore the connection between the contacts. Be sure to use refractory solder; others simply will not withstand the temperature that the heater will produce during operation. Of course, under standard conditions the degree will not be more than one hundred, but a reserve still needs to be made.
The choice of solder should be taken as responsibly as possible. It is better to purchase lead-free solder with a high melting point (from 200 degrees). You can order a suitable one online.
The next step is to purchase a special soldering iron for lead-free solder. Can be ordered:
soldering station;
adjustable soldering iron with ceramic heating element.
Also, for soldering with lead-free solder, conventional soldering irons manufactured in accordance with GOST 1969 or 1977 with a power of 65 Watt are suitable. Having prepared everything you need, you can start working:
secure the heating element between two pliers;
remove all fatty deposits and dirt from the treated area;
Apply soldering acid to the supply path;
Fill the entire section of the old contact track with lead-free solder;
check the thermal stability of the dielectric (the soldering iron should not melt it).
At this point the soldering process can be considered complete. Next, you will need to check the heating element for functionality. This can also be done using a multimeter.
Checking the heating element after soldering
To understand whether soldering helped, you need to re-measure the resistance between the supply contacts of the heating element. Attach the multimeter probes to the corresponding terminals - normally the values on the device screen should be 22-25 Ohms. Also check that there is no resistance to the ground.
Then the functionality of the thermocouple is checked. It is necessary to measure the resistance between the first and second, second and third, first and third contacts. This can also be done with a multimeter.
The sum of the resistances between pins 1 and 2, pins 2 and 3 must match the resistance between the first and third pins.
If the values on the ohmmeter screen correspond to the standard values, the heater repair can be considered complete. Next, all that remains is to reassemble the recirculation pump and the Bosch dishwasher itself. We'll tell you how this is done and what difficulties you may encounter.
Putting the circulation pump back together
First of all, the part of the recirculation pump is assembled, where the heater is built in. First, you need to secure a metal casing in the plastic case. Since the rivets have been drilled out, you will have to use screws to connect the two pieces.
The algorithm of actions will be as follows:
insert the metal casing into the plastic case;
Drill holes through in three places to screw in the bolts;
lubricate the rubber seal with vegetable oil;
put the ring on the base of the heating element (if you first put the seal on the bottom of the housing and then install the heater, the element will not “sit” as it should);
insert the heating element with the sealing ring in place into the pump housing;
dull the slotted screwdriver with sandpaper so that you can use it to push the seal deep into the body without damaging the gasket itself and the heating element;
using a screwdriver, “press” the sealing rubber evenly into the base of the housing;
screw the screws into the previously prepared holes to connect the casings, secure them with nuts;
Connect the two halves of the Bosch dishwasher recirculation pump together.
If you encounter difficulties with the connection, try removing the seal from one part and putting it on the half with the heating element. After this, the latches should work. Inspect the structure to make sure it is sealed. The pump terminal blocks must be located in the same plane.
After this, you need to assemble the Bosch dishwasher. First, the recirculation pump is put in place, water pipes and electrical connectors are connected to it. Then the bottom of the dishwasher goes back.
After replacing the panel of water and sewer hoses, reattach the lower housing flap. After this, you can turn the machine over to its normal position.
Once the dishwasher is completely assembled, run a test cycle. The machine should wash and dry the dishes without producing errors. In this case, you can attach the PMM to the headset and continue to use the “home assistant” as before.
The PMM heating element fails quite often. This is due to the low quality of tap water in most Russian regions. On modern Bosch dishwashers, heating elements “live” for about two to three years, then repair or replacement of the part is required.
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