Massey Ferguson AC27 – Air Conditioning Control Module (AIRCON): Issue With Signal To Left Cab Fan Speed Controller

The system logs this code when the signal to or from the left cab fan speed controller (potentiometer/resistor) falls outside of its expected operating range.

• 7616
• 5612
• 7622
• Interim Tier 4 (2012-2015)
• 7614
• 5611
• 7615
• 5610
• 5613
• 7620
• 5609
• 7618
• 5608
• 7619
• 7626
• 7624
• 4707
• 4708
• 4709
• 4710
• 5400
• 5710SL
• 5711SL
• 5712SL
• 5713SL
• 7714
• 7715
• 7716
• 7718
• 7719
• 7720
• 7722
• 7724
• 7726
• 8670
• 8690

1. 1

   Inspect the Left-hand fan adapter module (X445) physical connector for corrosion, pushed-out pins, or moisture.

2. 2

   Check the main Air Conditioning Control Module connectors (X439 blue and X440 yellow) for secure fitment and voltage irregularities.

3. 3

   Test the wiring harness between the AIRCON module and the X445 adapter module for continuity, looking for shorts to ground or open circuits.

4. 4

   Verify the resistance values of the left cab blower motor resistor to ensure it has not failed internally.

1. 1

   Disconnect Power

   Turn off the tractor and disconnect the battery to prevent electrical shorts during repair.

2. 2

   Access the HVAC Unit

   Remove the necessary cab roof panels or headliner to access the cab blower motors and the AIRCON control modules.

3. 3

   Repair Wiring

   If the diagnostic checks revealed a broken wire or corroded connector at X445 or X439, repair the wiring harness or replace the pigtail connector.

4. 4

   Replace the Speed Controller/Resistor

   If the wiring is intact but the signal is still out of range, remove the faulty left cab fan speed controller (blower motor resistor) or the X445 adapter module and install the replacement part.

5. 5

   Reassemble and Test

   Reconnect the battery, turn on the tractor, and test the HVAC fan speeds manually and in automatic mode.

6. 6

   Clear Codes

   Use a diagnostic tool to clear the AC27 fault code from the AIRCON module.