[Dorothy Noyes]

washes dishes fine, leaves very bad heavy film on glass even after an addition rinse

[denman]

Did this just start happening?
Have you changed your detergent recently?
Do you use rinse aid?

If the above are Yes, NO, Yes
Then I would get a bucket and drain some water out of your water tank.
Over time scale and minerals collect in the bottom of the tank
Drain it it you get nice clean water
Then run at least one rinse only to clear the pipes going to the dishwasher