One of the latest in a string of ways that appliance manufacturers increase internal space and reduce cost is what we call heat pumps in dishwashers, we explain it
These units are essentially the main wash motor of the dishwasher with the heater or heating element integrated into the pump unit itself, often in one unit that can only one replaced, as one complete unit.
So if the motor fails, it's the whole unit you need to change and, same if as is more commonly the case, the heating element part of it fails, it's a complete unit that is needed.
Some of these are not too bad in terms of price, some are frankly horrific.
They're not hard to change as such, the biggest issue normally is getting to them as they can be in very densely packed and difficult to reach areas in the bowels of your dishwasher.
Why They Fail
They are, like any part, just a part and can fail like a light bulb without any real reason. Heating elements, of course, are one of those things that, like a light bulb, can just pop for any number of reasons.
But a current running theory with the repairers because they seem to fail more in hard water areas is that limescale build up is causing hot spots on the element and causing them to blow. Whether this is correct or not, we can't say for sure but anecdotal evidence would certainly make for a reasonably strong case that this was a reason.
Why Can't I Get Parts Of It?
Dead simple, it's not worth making them.
For the brand it's normally a case of they buy these in pre-assembled from a third party supplier, they don't make them so it's not worth anyone's time to make parts available for them, it's way easier to just supply a full unit.
Of course, some are sealed up and you can't replace the heater anyway even if you wanted to.
The only party that would benefit is the customer and, when it comes to self-servicing of appliances, we know that most manufacturers really don't appear to give a stuff about that.
And, for manufacturer service, it's a whole lot easier as it's one part to stock and only one part to replaced making things easier, cheaper and faster. For them at least.
We do have to point out that one manufacturer, Electrolux (AEG, Zanussi etc), made a U-turn on this and made the heating element part of at least a few of these heat pump assemblies available as a separate spare part so, hat's off to them for doing so.
Whilst only a single instance of this having been done, it proves that it can be done so we suspect, but have no way to prove, that others could do likewise if they wished to do so.
In fairness to BSH Group (Bosch, Neff, Siemens) have made these parts cheaper than we'd ordinarily expect them to be and we suspect that's as they have proved to be problematic but that is a bit of a guess.
When it comes to ordering a replacement heat pump though you do need to take a bit of care as because they are sealed and set up for use in a particular cabinet means that it has to be correct or, it will not fit.
When you look for a replacement you need to be able to "read" spare parts as there will often be multiple versions of any given model, often using multiple heat pumps and not uncommonly with changes in productions to boot meaning it can be a proper pain to track down the exact one required.
The message here is really simple, take care and check carefully or ask a supplier like ourselves to do so for you as it's too easy to get it wrong and, they all look alike so you'll often not be able to tell what one is needed from images alone, as is the case with a great many spare parts.