Massey Ferguson 10.03.09 – AIRCON: Air Conditioning Evaporator Temperature Sensor Open Circuit

The control module is not detecting a continuous electrical path through the evaporator temperature sensor, which usually indicates a broken wire, a disconnected plug, or a completely failed sensor. As a safety consequence to prevent the evaporator core from freezing over, the air conditioning system is automatically turned off and cooling is disabled.

• 7724S
• 5712SL
• 7722
• 7722S
• 5713SL
• 7720S
• 7716
• 7718
• T4
• 7715
• 5710SL
• 7726
• 7726S
• 5711SL
• 7718S
• 7719
• 7714
• 7716S
• 7720
• Tier 4 (2015-2021)
• 7715S
• 7724
• 4700 series
• 5700 series
• 6700 series
• 4707
• 4710
• 6713
• 5600 series
• 5608 through 5613
• 7600 series
• 7700 series
• 7614 through 7626
• 7714 through 7726S
• 8600 series
• WR9950
• WR9960
• WR9970
• WR9980

1. 1

   Visually inspect the wiring harness leading to the evaporator temperature sensor for chafed wires, rodent damage, or a disconnected plug.

2. 2

   Inspect the sensor connectors and the AIRCON module pins for corrosion, moisture, or backed-out pins.

3. 3

   Unplug the sensor and measure resistance across its terminals using a multimeter. Infinite resistance (OL) indicates a failed sensor, while a normal thermistor value (kOhm range) indicates a wiring harness fault.

4. 4

   Use the AGCO Electronic Diagnostic Tool (EDT) to monitor the live signal accuracy of the sensor while wiggling the wiring.

5. 5

   Inspect the evaporator core for packed dirt and mud, cleaning it to ensure accurate temperature readings once repaired.

1. 1

   Access the HVAC Unit

   Locate the HVAC housing. Depending on the tractor model, this is typically located either in the cab roof (headliner removal required) or under the cab seat.

2. 2

   Locate the Sensor

   Find the evaporator temperature sensor. It is a probe-style sensor that is physically inserted directly into the fins of the evaporator core.

3. 3

   Remove the Faulty Sensor

   Disconnect the electrical pigtail connector. Carefully pull the sensor probe straight out of the evaporator fins.

4. 4

   Install the New Sensor

   Gently insert the new temperature sensor probe into the exact same location in the evaporator fins. Ensure it is seated deeply enough to accurately measure the core temperature without puncturing a refrigerant tube.

5. 5

   Reconnect and Reassemble

   Plug the electrical connector back in. Reassemble the HVAC housing and cab interior panels.

6. 6

   Clear Codes

   Turn the ignition on. The code may move from 'Active' to 'Stored' automatically once the circuit is restored. If the AC compressor does not engage, use the AGCO EDT to clear the stored fault codes.