Bosch dishwasher does not heat water - what to do?

PMM Bosch does not heat water If the Bosch dishwasher does not heat the water, there is no need to rush to disassemble it in order to check the heating element. For some reason, it is obvious to the average person that if the machine refuses to heat the water, then the heating element is definitely to blame. In reality, the reasons may lie elsewhere, but of course the heating element cannot be ruled out.

Broken or not?

Before you rush to disassemble your Bosch dishwasher, there are a few obvious things you should check. Firstly, if the dishwasher is completely new and was recently put into operation, you need to look at how it was connected to the water supply. The fact is that Bosch dishwashers have two outlets for the inlet hose: for hot water and for cold. If you mix up the inputs during installation, the machine will think that hot water is coming in instead of cold and will not heat it up. If you connect the inlet hose correctly, the problem will be resolved.

The machine may stop heating water if the user made mistakes during its operation. In particular, if the wrong program was selected or, most likely, the garbage filter was not cleaned in time. Blockages in the system can disrupt the circulation of water, which in turn leads to the machine starting to wash dishes intermittently and with cold water. The bottom line is this: you need to look at the instructions and make sure that you are choosing the right washing program. In addition, you need to clean the garbage filter and make sure there are no deeper clogs.

After unscrewing the garbage filter, look into the resulting niche and if you find dirt there, remove it.

If you are sure that you did not make operational errors, then most likely some kind of breakdown has occurred. There are a lot of possible options, let’s try to list the main ones.

Thermostat is faulty. A typical problem with Bosch dishwashers. Due to a faulty thermostat, the control module receives incorrect information about the water temperature. In this case, the module either does not turn on the heating element at all and then the water remains cold, or it runs it constantly, and then the machine washes the dishes with boiling water all the time.
The heating element is faulty. After reading the article Spare parts for Bosch dishwashers, you can make sure that the heating element in the Boški is connected to the recirculation pump. Therefore, if the heating element fails, the entire assembly has to be replaced. Fortunately, the heating elements of these machines do not break often.
The control module has failed. If the tire responsible for the heating element burns out, then this will be enough to prevent the heating element from turning on and the water remains cold.
There were problems with the electrical wiring. The conductors that supply the recirculation pump with a heating element and the thermostat can also cause dysfunction of these parts. It is enough for one wiring to fray or jump out of the chip, the water will stop heating.

Failure search algorithm

First you need to disassemble the dishwasher to gain access to the tray parts. You can read about how to do this in the article. How to fix error E14 in a Bosch dishwasher, now we will not focus on this.

After removing the Bosch dishwasher tray, you should take a multimeter and check all the parts from the list of suspects one by one. We won’t go into the control module, because its repair and diagnostics require special knowledge.First, we disconnect the chip with wires from the recirculation pump, and then measure the resistance at the input. The resistance of a working pump together with a heating element will be about 25 Ohms, depending on the specific model, but not lower than 18 Ohms. Significantly lower resistance values will indicate that the part is broken and needs to be replaced.

Next we check the thermostat. We also disconnect the wires from it and take measurements. The resistance to the input of the thermostat at room temperature is 6000-4700 Ohms; if it shows less, it means that the problem is hidden in the thermostat. If both of these details do not arouse suspicion, you should pay attention to the wiring. Start with a visual inspection. Burnt, frayed or fallen wires will not escape a close look. Don’t be lazy to spend a little more time looking at the wiring.

If visual damage cannot be detected, you should again arm yourself with a multimeter and check each wire for breakdown. It is very possible that somewhere the wiring broke under the insulation, which created a lot of trouble for you. If faulty wiring is detected, it must be replaced.

We fix the problem ourselves

What to do when a breakdown is discovered? Some novice DIYers suggest restoring the heating element in the recirculation pump. This repair option seems very doubtful to us, so we see no other solution other than replacing the entire assembly. First, we look at the part number and use this number to order exactly the same one on the Bosch website, this will turn out to be 15-20% cheaper. We disconnect the old pump and put a new one in its place, nothing fancy.

We do the same with the thermostat, but if you suspect that one of the control board buses is faulty, feel free to call the service center. Self-diagnosing the failure of the control board, and then carrying out high-quality repairs are within the power of only a few. There is no need to risk an expensive part.

So, in most cases, you can determine why a Bosch dishwasher does not heat the water yourself. At the same time, you can actually save $100, especially if you carry out diagnostics and repairs with the utmost care and thoughtfulness. Good luck!