Massey Ferguson AC24 – Air Conditioning Control Module: Engine speed error

The Air Conditioning Control Module is not receiving the required engine speed information over the CAN bus network. The AC module relies on this engine speed signal to determine if the engine is running (to safely engage the AC compressor) and to calculate compressor load and speed.

• 7616
• 5612
• 7622
• Interim Tier 4 (2012-2015)
• 7614
• 5611
• 7615
• 5610
• 5613
• 7620
• 5609
• 7618
• 5608
• 7619
• 7626
• 7624
• MF 7614
• MF 7615
• MF 7616
• MF 7618
• MF 8670
• MF 8690

1. 1

   Verify Engine ECU Output: Ensure the engine is broadcasting its speed by checking the dash tachometer and scanning the Engine ECU for any primary engine speed sensor faults.

2. 2

   Inspect Connectors: Locate the Air Conditioning Control Module and inspect the X440 (yellow) and X439 (blue) connectors for backed-out pins, corrosion, or moisture ingress.

3. 3

   CAN Bus Wiring Test: Test the CAN bus lines between the Engine ECU / main CAN hub and the AC module for continuity, shorts to ground, or shorts to power.

4. 4

   Check Terminating Resistors: Verify the CAN bus network integrity by measuring the resistance across the CAN High and CAN Low pins (should typically read around 60 ohms with the battery disconnected).

1. 1

   Disconnect Power

   Turn off the ignition and disconnect the tractor's battery to prevent electrical spikes during repair.

2. 2

   Access the Module

   Locate the Air Conditioning Control Module (typically located in the cab console or roof, depending on the exact cab configuration).

3. 3

   Disconnect and Clean

   Unplug the X440 (yellow) and X439 (blue) connectors. Use a high-quality electrical contact cleaner to clean the pins on both the module and the harness side.

4. 4

   Repair Wiring

   If the diagnostic checks revealed a break or short in the CAN bus wiring, splice and repair the damaged section using appropriate heat-shrink connectors, or replace the damaged pins in the X440/X439 connectors.

5. 5

   Reassemble and Test

   Reconnect the X440 and X439 connectors to the AC module. Reconnect the battery.

6. 6

   Clear Codes

   Connect a diagnostic tool (such as AGCO EDT or Jaltest) and clear the AC24 fault code.

7. 7

   Operational Check

   Start the engine. Verify that the AC24 code does not return and that the air conditioning compressor engages normally when commanded.