Check Radiator Fan Circuit
electrical
Description
The radiator fan relay output and FET feedback voltage do not match, and the unit alarms only.
Activation Conditions
Trigger On Radiator Fan relay Output is ON and FET Feedback Voltage is below Minimum ON Threshold OR Radiator fan relay Output is OFF and FET Feedback Voltage is above Maximum OFF Threshold. Trigger Off If alarm was active when Radiator Fan Relay was ON, trigger OFF if Output is ON and FET Feedback Voltage is sensed in Active range OR If alarm was active when Radiator Fan was OFF, trigger OFF if Output is OFF and FET Feedback Voltage is sensed in Inactive range OR Alarm Reset OR Cycle Power
Unit Behavior
Alarm only
Reset Conditions
Alarm reset OR Cycle Power
Corrective Actions
1. Open CabinTech system values and verify if 00076 occurs when the radiator fan output is ON or OFF. If ON go to step 2. If Off go to step 4 2. Measure resistance between SAR-1 and SAR-3 (radiator fan side of connector). a. If resistance is > 90Ω ±10%, recheck resistance between Radiator Fan Relay (RFR) 85 and 86. b. If resistance = 90Ω ±10%, go to step 3 3. Measure resistance between SAR-A and APU J2-11 a. If resistance is > 1.0 Ω inspect harness and connections between APU module and SAR connector. b. If resistance is < 1.0 Ω go to step 5. c. Yes step 3 NO replace fan 4. Measure radiator fan output voltage - Measure voltage at APU J2-11 when radiator fan output is OFF. Is voltage > 5.0 volts? If NO go to step 5. 5. Replace APU module a. Remove wire from APU J2-11. Measure voltage between terminal and ground. Is voltage > 0.5 VDC? If yes check for short to power between APU J2 and RFR.