Repair work at the inner and outer chamber
7.10 Checking and replacing the humidity sensor and the sensor board
(-3B2)
Spare parts:
Humidity sensor long with sensor board F2CX (order no. 5002-0143)
Cable access port (order no. 6005-0112)
Screwed cable fitting (order no. 6002-0398)
PU foam (order no. 1004-0009)
Necessary tools
Crosstip screwdriver, size 2
Multimeter measuring device
Hygrometer
Fork wrench, size 30/32
Universal cutter
Side cutter
The humidity sensor and the sensor board have been calibrated together. For this reason
always replace them together.
1.
Disconnect the unit from the power supply.
2.
Remove the housing cover of the lower front (chap. 5.1).
3.
Pull the bottom electric mounting plate out of the unit (chap. 8.5).
Checking the humidity sensor (-3B2)
4.
Remove the wire from the conn10, (E4 / 4-20 mAmp) on the controller MB1 I/O-board
(-3N2) (see wiring diagram). Use an ampere meter connected in series to measure the current between
the free cable ending and the controller MB1 I/O-board (for this purpose, connect the unit temporarily to
the power supply and switch it on).
5.
The measured current should be in the range between 4 mAmp and 20 mAmp (
≙
0 – 100 % rel. humidi-
ty). Refer to Table 3 to determine the air humidity corresponding to the measured current value. Compare
this value with the reference measuring value of a hygrometer placed inside the unit. If the deviation is
more than 20 % the humidity sensor is defective and must be replaced.
6.
Disconnect the unit from the power supply.
7.
Remove the rear housing panel (chap. 5.3).
8.
Pull the contactor from the connection -20, (voltage output 45 mAmp / 24V DC) of the controller MB1 I/O-
board (-3N2) (see wiring diagram).
9.
Pull the wire of the humidity sensor from the connection -11 (E4 / 4 - 20 mAmp) on the controller MB1 I/O-
board (-3N2) (see wiring diagram).
10.
Detach all cable holders and cable ties of the humidity sensor in the machine room and at the unit rear.
11.
Remove the inner chamber (chap. 7.7).
12.
Remove the cable access port sealed with silicone (B) from the left spoiler.
13.
Remove the left spoiler (chap. 7.7).
Service Manual KBF (E5.2) 04-2015
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