ENGINE AR-PRIMARY 2247498 - Caterpillar

Diagnostics
Measure the value of the resistance in the servo motor between L GN/YL and PU/YL. See "Specifications". Proceed to step 2.
If the resistance value is incorrect see step 3. If the resistance value is correct see step 4.
Replace the servo motor.
Disconnect the connectors from the servo motor and measure the voltage between the connectors PU/YL and L GN/YL. See "Specifications". Proceed to step 5.
If the voltage value is incorrect see step 6. If the voltage value is correct see step 7.
Check the harness and repair the harness between the connector and the control unit. Also, check the power source of the system.
Reconnect the servo motor to the harness. Measure the voltage at the connector of the control panel between terminal 27 and the corresponding discharge damper in Table 1. Refer to "Specifications". Proceed to step 8.
If the voltage values are incorrect see step 9. If the voltage values are correct see step 10.
Check the harness and repair the harness between the connector and the control unit.
Replace the control unit.Specifications
Resistance ... 6 kOhmsVoltage between connectors ... 5.0 V
Table 1
Voltage Specifications (Face 2 Mode) (1)    
    Terminals at the Control Unit     Voltage    
Discharge outlet changeover damper     9, 27     4.67 V    
DEF changeover damper     10, 27     4.5 V    
FACE changeover damper     11, 27     5.0 V    
( 1 ) Face 2 Mode is the air outlet for Upper Body and Under Seat.