How can I fix a heating problem in my Whirlpool ADP905?

Not sure if this is the same as mine ADP: to get into service mode, turn it "off" on the front panel, then hold down the start button whilst turning it on. After a few sceonds the start light starts flashing. Then you release the start button, and it does a simple indicator test. Press the start button to begin the passive test; press it again to begin the active test.

The tests display a fault code based on the LED's which you can decode to see what's wrong. But you need the service manual to know what the codes mean - trying googling it and you'll probably fine one to download for free or for $10.

Dr Mark
August 2007