Massey Ferguson AC09 – Air Conditioning (HVAC) Control Module: Evaporator temperature sensor (X443) - Sensor open

The circuit for the air conditioning evaporator temperature sensor has an open connection, meaning the controller is receiving infinite resistance or no signal from the sensor. When this open circuit is detected, the system defaults to a protective state, automatically turning off the air conditioning compressor and disabling cooling to prevent system damage.

• 7616
• 5612
• 7622
• Interim Tier 4 (2012-2015)
• 7614
• 5611
• 7615
• 5610
• 5613
• 7620
• 5609
• 7618
• 5608
• 7619
• 7626
• 7624
• 7600 Series
• 7617
• 8600 Series
• 8670
• 8690
• 5400 Series
• 6400 Series

1. 1

   Connect a diagnostic PC or the AGCO Electronic Diagnostic Tool (EDT) to monitor the live signal accuracy of the evaporator temperature sensor (X443).

2. 2

   Inspect the wiring harness and connectors leading to sensor X443. Look for disconnected plugs, backed-out pins, broken wires, or corrosion that would cause an open circuit.

3. 3

   Disconnect the sensor and use a multimeter to measure the resistance across the sensor's pins. If the multimeter reads 'OL' (open loop/infinite resistance), the sensor itself has failed internally.

1. 1

   Access the Sensor

   Locate the evaporator temperature sensor (X443), which is typically inserted into the fins of the A/C evaporator core inside the cab's HVAC unit.

2. 2

   Inspect and Clean

   Disconnect the sensor's electrical connector. Clean the contacts with electrical contact cleaner.

3. 3

   Test the Harness

   If the sensor tests good (shows proper resistance), use a multimeter to check for continuity on the wiring harness between the sensor connector and the HVAC control module. Repair any broken wires.

4. 4

   Replace the Sensor

   If the sensor tests as an open circuit, remove the faulty sensor from the evaporator core and install a new OEM replacement.

5. 5

   Reassemble and Clear Codes

   Reconnect the wiring harness, reassemble any removed HVAC covers, and use your diagnostic tool to clear the AC09 fault code.

6. 6

   Verify Operation

   Start the tractor and engage the air conditioning. Verify that the A/C compressor clutch engages and that the system blows cold air, confirming the controller is no longer disabling the cooling function.