Bosch KGU3201GB/07 – auto defrost problems

We’ve got a 1998 Bosch KGU3201GB/07, which is still working, but suffering from ice build-up.

Following the excellent info posted for a similar model on this thread: fridge-freezer-forum/bosch-kgu3201gb-defrost-problems-t60815.html

I’ve investigated what’s going on. The main defrost heater seems to be working, as it’s dropping chunks of ice down onto the metal tray below. However these are freezing into a solid block which is sealing the exit hole.

I’ve measured the resistance of the lower tray heating element as 2.2k ohm, which seems about right – that should take 25 watts at 230v ac.

I’ve also tested that it switches on/off using test program P04.

I’ve run it overnight, with the door closed – taking external leads out to test when the controller switches the heater on. I found that I needed the back panel on, and care in sealing round the door, where the leads came out. Sure enough, it switched on at 2.30am last night.

We’re running on the “timed defrost” P11 = “CF” mode, as described elsewhere. Looks like we only get a defrost once per 24 hours.

For the moment I’ve put it back together and will monitor to see if we still get ice build-up.

Just two questions at this stage:
– Does anyone have a list of all the test programs?
– Does it seem right that we get only one defrost per 24 hours?