My Bosch dishwasher isn't heating water—what should I do?

If your Bosch dishwasher isn't heating water, don't rush to disassemble it to check the heating element. For some reason, it's obvious to the average person that if the machine refuses to heat water, the heating element is the culprit. In reality, the cause may lie elsewhere, but the heating element certainly can't be ruled out.

Is it a breakdown or not?

Before you rush to disassemble your Bosch dishwasher, there are a few obvious things you should check. First, if the dishwasher is brand new and has only recently been installed, you should check how it's connected to the water supply. Bosch dishwashers have two inlet hose connections: one for hot water and one for cold. If you mix them up during installation, the machine will think it's receiving hot water instead of cold and won't heat it. Connecting the inlet hose correctly will solve the problem.

The machine may stop heating water if the user makes mistakes during operation. This includes selecting the wrong program or, most likely, not cleaning the debris filter promptly. Blockages in the system can disrupt water circulation, which in turn causes the machine to wash dishes intermittently and with cold water. The bottom line is, check your instructions and make sure you're choosing the right wash cycle. In addition, you need to clean the debris filter and make sure there are no deeper blockages.

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

If you're sure you haven't made any operating errors, then it's likely that something is wrong. There are many possible causes, so let's try to list the main ones.

1. A faulty thermostat. A common problem with Bosch dishwashers. A faulty thermostat causes the control module to receive incorrect water temperature information. In this case, the module either doesn't turn on the heating element at all, leaving the water cold, or it constantly runs the heating element, causing the machine to wash dishes with boiling water.
2. The heating element is faulty. After reading the article Spare parts for Bosch dishwashers, you can see that the heating element in Boshki is connected to the recirculation pump. Therefore, if the heating element fails, the entire unit must be replaced. Fortunately, heating elements in these machines don't fail often.
3. The control module has failed. If the busbar responsible for the heating element has burned out, this will be enough to prevent the heating element from turning on, and the water will remain cold.
4. There are problems with the electrical wiring. The wires supplying the recirculation pump, heating element, and thermostat can also cause these components to malfunction. It only takes one wire to fray or pop out of its connector, and the water will stop heating.

Fault detection algorithm

First, you need to disassemble the dishwasher to access the drip tray components. You can read about how to do this in the article. How to fix the E14 error on a Bosch dishwasher, we won't focus on this now.

After removing the Bosch dishwasher tray, take a multimeter and check each suspect component one by one. We won't touch the control module, as repairing and diagnosing it requires specialized knowledge. First, disconnect the wiring from the recirculation pump and then measure the input resistance. The resistance of a running pump and heating element will be around 25 ohms, depending on the specific model, but no lower than 18 ohms. Significantly lower resistance readings indicate that the component is broken and needs to be replaced.

Next, we check the thermostat. We also disconnect the wires from it and take measurements. The thermostat input resistance at room temperature is 6000-4700 ohms. If it reads less, the problem lies with the thermostat. If both of these parts do not raise any suspicions, it is worth paying attention to the wiring. Start with a visual inspection. Burnt, frayed, or missing wires won't escape a close look. Don't be lazy, spend a little extra time examining the wires.

If you can't find any damage visually, it's worth using a multimeter again and checking each wire for continuity. It's quite possible that a wire has broken under the insulation, causing a lot of trouble. If faulty wiring is detected, it should be replaced.

Fixing the problem yourself

What should you do once you've discovered the problem? Some DIY enthusiasts suggest repairing the heating element in the recirculation pump. We find this repair option highly questionable, so we see no other solution than replacing the entire unit. First, we look up the part number and use it to order an identical one from the Bosch website; this will save us 15-20%. Disconnect the old pump and install the new one in its place—no big deal.

We'll do the same with the thermostat, but if you suspect a problem with one of the control board buses, don't hesitate to call a service center. Very few people can independently diagnose a faulty control board and then perform a high-quality repair. Don't risk damaging an expensive part.

So, in most cases, you can determine why your Bosch dishwasher isn't heating water yourself. This can actually save you several tens of dollars, especially if you conduct diagnostics and repairs with the utmost care and attention. Good luck!

   

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