Troubleshooting
Condensation on the glass door
and / or the outer door
Does the outer door fit closely? No Adjust the outer door (chap. 6.1, page 41)
Yes
Outer door gasket and / or glass door gasket
defective?
Yes Replace outer door gasket and / or glass
door gasket (chap. 6.2.4, page 49 and
chap. 7.5, page 62)
No
Solid state relay (-4K2) defective?
Door heating and frame heating without func-
tion
Yes
Replace solid state relay, (chap. 8.6,
page 82)
No
Power relay (-5K2) defective?
Complete heating without function
Yes Replace power relay
(chap. 8.6, page 82)
No
Door heating cable (-4E2) defective?
Measure resistance at contactor (–X50) pins 1 +
2.
Yes
Replace interior side of outer door
(chap. 6.2.3, page 46)
No
Frame heat conductor (-4E3) defective?
Measure resistance at contactor (–X50) pins 3 +
4
Yes
Replace frame heat conductor
(chap. 7.6, page 63)
No
Controller MB1 I/O-board (-3N2) defective?
The binary output BA 4 (0 - 5 V DC) is non-
functional.
Yes
Replace controller MB1 I/O-board
No
Temperature sensor Pt 100 (-3B3) in the
interior side of the outer door defective?
(Connection to E2 on controller MB1 I/O-
board). Check the temperature sensor
(chap. 6.2.3, page 46)
Yes
Replace interior side of outer door
(chap. 6.2.3, page 46)
22 Service Manual KBF (E5.2) 04-2015
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