Applies to:

Calibrating and Replacing Humidity Sensor

The humidity sensor detects the cabinet humidity and relays that information to the controls. If it becomes faulty, "E-17", then "HUMIDITY SENSOR FAILED" displays. Replace sensor as follows:

To avoid electrical shock or property damage, disconnect power before installing or servicing equipment. A qualified technician must perform the service procedures.

Replacement:

Open operator side door of unit.
Using a crosshead screwdriver, remove the front screw and loosen the 2 side screws securing the sensor cover. Slide cover towards you and over loosened screws.
Using a 1-3/16" wrench, remove nut.
Using a crosshead screwdriver, remove the four screws securing the front panel.
Lower panel, remove connectors from the back, and remove panel from unit.
Pull the sensor assembly from the top of the cabinet.
Remove strain relief from old sensor and install on new sensor.
Connect wires to control panel and re-install panel. Perform sensor calibration using below instructions before installing sensor cover.
After calibration is complete, install cover.

Calibrating:

Calibrate the humidity sensor after a sensor or control replacement. A calibration board is supplied with each control kit and humidity sensor kit, but can also be ordered separately under part number 14391.

AHC-993 ONLY (AHC-990 continue onto step 12)

Unscrew the silver cap from humidity sensor.
Remove the two pronged sensor by grasping the edges.

Touching the flat side will throw the reading off. Try not to touch the flat side.
Press and hold PROG button until "Level 2" displays.
Press PROG button to step through the menu until "TECH' displays.
Using the hidden buttons, enter code of 11221122.
Press PROG button to step through menu to "HUMIDITY--CIRCUIT CAL".
Insert the two prongs of the calibration board marked 20% into the humidity sensor.
Press and hold hidden button 1, then press Down arrow button . Release both buttons. a 4-digit number between 55.00 & 75.00 should display.
Reverse calibration board and insert the two prongs marked 80% into humidity sensor.
Press and hold hidden button 2 then press Down arrow button . Release both buttons. a 5-digit number around 110.00 & 130.00 should display.
Press PROG button until "HUMIDITY SENSOR -- CALIB/OFFSET" displays.
Find the offset number on the mounting plate of the humidity sensor.
Press and hold hidden button 2, and press Up arrow button or Down arrow button to enter offset value.
Press and hold PROG button to exit Tech Mode.
Remove calibration board from controller and replace with humidity sensor connector.
Reinstall controller on unit and unit is ready for operation.