dry white residue

After ten years of good service, our Bosch dishwasher has started to leave dry white powdery (flavourless i.e not salty or chemicaly) residue on our washed crockery.
Is the salt bay not working?
The rinse aid not working ?
The service line Bosch recommend (spares suppliers) recommended trying all Finish products (rinse-aid, detergent) but that hasn\\\'t solved it.
We live in hard water area. There doesn\\\'t appear to be any blockages + we have checked the filters.
We think the salt bay on the inside of the maching may not be working but it doesn\\\'t appear obviously broken, and the rinse aid unit looks ok as well.
Any ideas?
thanks

Sounds to me like the internal water softener is not working, leading to limescale deposits. i suppose you could check this theory with a bit of vinegar on the scale.

The chemical softener granules are refreshed with the salt.

JohnD - is the 'internal water softener' that you refer to, separate from the salt box on the inside wall of the machine, and separate from the rinse aid cell on the inside of the door? I assume so ...
in which case, is this the job of an engineer or does this mean 'new machine' time?

also, if I just put a bit of 'vinegar on the scale', that just gives the interior a one-off clean doesn't it, as opposed to making sure every wash is good?

finally (!) when you say 'the chemical softener granules are refreshed with teh salt', what does this mean?

thanks for your help

I live in a very hard-water area so have a whole-house softener, that makes it easier to see what is going on.

the dishwasher has a miniature water softener in it. this is a vessel containing granules of a synthetic resin that absorms calcium from the water. The calcium salts form limecale if not removed.

What happens when the granules have absorbed so much calcium that they're "full" you wonder?

Well, by immersing them in a concentrated solution of salt water, the sodium in the salt displaces the calcium, and the calcium-filled waste water is then washed down the drain, and the softening cycle begins again. The softened water actually contains sodium salts, but like the sodium bicarbonate that you take for indigeston, it's water-soluble and doesn't form scale.

there will be some kind of control mechnism that decides when to wash salt through the granules, and taps that open and close to send the water out ofthe softener either down the drain or into the wash.

I expect something has gone wrong with the softener mechanism, and as your old Bosch has lasted 10 years, i think it's done its duty by you, time to look for another.

Very good machine, the Bosch, I'd get another if I were you.

p.s. - about the vinegar - if, as I suspect, the vinegard dissolves the white residue with a bit of fizzing, and it won't wash off with plain water, that encourages me to believe it's limescale due to a softener fault. It has nothing to do with rinse aid. I hope you are using proper granulated dishwasher salt, not kitchen salt or anything.

BTW I have never seen a salt box in the door or side of the cabinet. Unless yours is a different design, on a Bosch there is a screw-off plastic cap about 120mm across in the floor of the machine, visible when you slide or lift out the bottom tray. You take the cap off and tip the salt granules down there. It may possibly have a blue float inside, when you can see the blue through the cap it has enough salt; when it hasn't it needs refilling with salt. Have you had this machine since new, or obtained it used?

Mine has just started doing this too - happened very suddenly, went from working fine to everything being covered in white redidue in the space of one wash. Now it's always doing it. This is also a Bosch, around 6 years old I think.

So I'd be interested to hear if you found a solution to the problem.

One thing that has just crossed my mind is that I will check the level of salt manually (or maybe just top it up anyway) - the "salt" light hasn't come on, but it seems like ages since I last filled it. I wonder if the bulb/LED that indicates "salt low" has blown...

Anyway, please let me know if you had any luck fixing the problem, as it looks like I have the same problem.

The most common form of white film is due to limescale and is attributable to the water hardness.

Lime scale film can be removed by adding a small quantity of citric acid (40grams) to the dispensor and doing a wash cycle.

Silica film is impossible to remove. Where detergents with a high level of disilicate are used, it can produce a white film also. In these cases the silica chemically bonds to the inner surface of the dishwasher.

Try doing several maintenance washes to remove limescale build up. Ensure the salt pot is full, and adjust your water softner to the correct level for the area you live. The water board will advise you of the local water hardness measurement. Manually clean your filters of any deposits.

Switch to a phosphated detergent such as Fairy if you have Silica film.

The water softner is flushed during "Regeneration" normally toward the end of cycle, this brine is pumped away without being sprayed onto the pots.
A full salt pot should usually last 20 to 30 washes depending on the make of appliance,as a general guide. If yours is longer then either a valve or the whole unit is faulty, and I would expect a Bosch dishwaser of 10 years of age to be full of life, yet. Well worth having it looked at by an engineer.

AF

I had a similar problem with a white powdery residue being left behind on the plates after washing. At first I also thought about limescale, but was puzzled because we live in a very soft water area - there is no scale in our 8 year old kettle for example. However I have found the actual cause is that the water in the dishwasher is no longer being heated. We use Finish 4 in 1 tablets that have a white part to them and basically they are not dissolving properly. We didn't realise the water wasn't being heated because the dishwasher still completes the cycle OK. I then found out there was a common fault on Bosch dishwashers whereby a pin on the relay for the water heater circuit would become unsoldered over time so I checked ours and found the water wasn't being heated. The DIY solution is to resolder the pin, a fairly easy job to do.

Hi, I know this is an old thread, but anyone know where the relay is that needs soldering? Been having this problem for ages and want to aviod forking out for a new DW.

it was on the control panel, but in the end I got a new control panel for about £100 in 2006.

DW is still going strong and it will be 13 years old on Monday !