When i bought my house it came with a dishwasher and it worked perfectly til about last june, it didnt drain, so in June i went out and bought another dishwasher and this one doesnt drain either, I have checked all the hoses for clogs or for collapsed hoses and found nothing. My garbage disposal works perfectly but my dishwasher doesnt want to drain,
To get two units with the same problem is highly unlikely so my guess is that you problem is in the house plumbing.
Was anything changed or added when the dishwasher stopped draining re: a new garbage disposal etc.?
You could undo the dishwasher at the disposal. Run a cycle and let it drain into a pail.
Be sure to hold the drain line securely into the pail and put a towel over it so it does not splash all over.
If it drains OK then you know the dishwasher is OK and you have a plumbing problem.