Massey Ferguson 23 – AC Module (AIRCON): Optional Cab Extra Fan Relay Signal From AC Module (AIRCON)

The air conditioning control system is detecting an anomaly—such as an open circuit, short circuit, or missing feedback signal—on the electrical circuit that controls the relay for the optional extra cab ventilation fan.

• 7724S
• Interim Tier 4 (2012-2015)
• 7722
• 7722S
• 7615
• 7720S
• 7716
• 7718
• 7726
• 7715
• 7616
• 7618
• 7619
• 7626
• 7726S
• 7624
• 7614
• 7718S
• 7620
• 7719
• 7714
• 7716S
• 7622
• 7720
• Tier 4 (2015-2021)
• 7715S
• 7724
• 4707
• 4708
• 4709
• 4710
• 5608
• 5609
• 5610
• 5611
• 5612
• 5613
• 5710SL
• 5711SL
• 5712SL
• 5713SL

1. 1

   Check the main cab fuse box for any blown fuses related to the HVAC system, cab accessories, or blower motors.

2. 2

   Test the Optional Cab Extra Fan Relay (typically in the cab roof electrical panel or main cab fuse/relay board) for constant 12V power on the main terminal and switched power on the control terminal.

3. 3

   Inspect the wiring harness and connectors between the AC Module and the relay for backed-out pins, corrosion, or chafed wires.

4. 4

   Use a multimeter to test the signal output directly at the AC Module to ensure it is sending the voltage required to trigger the relay.

1. 1

   Disconnect Power

   Turn off the ignition and disconnect the tractor's battery isolator switch before performing electrical repairs.

2. 2

   Clean Connections

   If the connectors at the AC Module or the relay block are dirty or corroded, clean them with electrical contact cleaner and ensure the pins are seated tightly.

3. 3

   Replace Faulty Components

   If the relay fails the bench test (e.g., the coil is open or the internal contacts are burnt), replace the relay. If the wiring harness is damaged, splice and repair the broken wires or replace the affected harness section.

4. 4

   Reassemble and Clear Codes

   Reconnect the battery. Use a diagnostic tool or the tractor's dashboard interface to clear the error code.

5. 5

   Test Operation

   Turn the AC system on and manually adjust the fan speed to verify that the extra cab fan engages and the code does not return.

6. 6

   Module Replacement (Worst Case)

   If the relay and wiring are perfectly intact but the AC module fails to output the signal, the AC Module itself has suffered an internal fault and will need to be repaired or replaced.