Dishwasher leaving crud on dishes- why?

[erebus]

Year old Bosch (no manual!), used mainly on the quick (30 min) cycle, but I am finding the dishes aren't coming out very clean, small grainy bits on them and the odd bits of food residue.

I clean the drain bit in the bottom of the machine but is there something else I should be cleaning?

TIA

i'd put it on an empty hot wash with detergent, the pipes and tubes may be blocked up with grease and crap.

clean the filters and run a hot wash to flush away any grease, etc

It might need the salt topping up, I had a rubbish dishwasher and had regular visits from the service guy who said you should use it even if you use 5 in one tablets etc! (I live in a hard water area not sure if this would apply elsewhere)

the salt was for the grainy bits, not the food residue by the way

Do you use tablets? I was told by the guy who installed my dishwasher that a 30 minute programme doesn't give enough time for the tablets to dissolve properly.

Thanks- and I amused that someone went to that much trouble! Replacing the door with a plastic panel to video a wash cycle!

Hot wash with a cup of soda crystals chucked in the bottom of the dishwasher.

I had this (grainy bits) and the repair men said it was dirt blocking the holes in the spray arms - apparently it's really common. We had them replaced but it didn't improve that much and we gave it away in the end.

Take off the spray arms (they should just unscrew) and wash them manually. An old toothbrush or something helps to clear the holes. Ours is a Bosch too and when it's not cleaning properly clogging of spray arms is usually the problem.