The Wrong Detergent
We often get asked on the phone and in the forums here on UK Whitegoods about what to do when people use washing up liquid in their dishwasher as, all of a sudden, it doesn't work any more or when the door is opened all you see is foam.
This is because your dishwasher was not designed to have washing up liquid put in it and dishwasher detergents foam far, far less than washing up liquids do. More often than not we get "I thought it would be okay as I'd ran out of tablets" well, we can assure you, it won't be okay.
What will happen is that the machine will massively overfoam causing foam to go where it shouldn't and the damage ranges from annoying but fixable to effectively writing the dishwasher off.
Here's a video on You Tube of a dishwasher doing just this.
As you can see, quite graphically, the amount of foam is considerable and regardless of the door being closed properly the foam still pours out. This is because dishwasher door seals are splash seals, they are not watertight or designed (generally) to hold in any volume of water, they merely stop the spray from leaking out.
So often the foam will go into the salt reservoir and wreck it, the base and burnt out the motor, at best tripping the safeties and a host of other things.
Solving it When It Happens
If it does happen about the only thing you can do is put the machine on a cold "“rinse and hold" program, although you may have to do this several times to clear it, and hope for the best. We say use the cold program as cold water breaks down the foaming far better than hot water which will only worsen the problem.
But if you're ever tempted to use some Fairy rather than wait, wash by hand or nip out to the supermarket for some proper detergent our advice is simply this, don't do it!