Massey Ferguson 25 – AC Module (AIRCON) / Climate Control Unit: No Vehicle Speed Information Received On The CAN BUS To AC Module (AIRCON)

The Air Conditioning (Climate Control) module relies on vehicle speed data broadcasted over the tractor's CAN bus network (usually sent by the Transmission ECU or Main Vehicle ECU) to regulate climate control functions. This code triggers when the AC module stops receiving these CAN messages, indicating a communication breakdown, a wiring fault, or a missing speed signal at the source.

• 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

   Verify the Speedometer: Check if the tractor's dashboard speedometer is working while driving. If the speedometer is dead or erratic, the root cause is likely a faulty Vehicle Speed Sensor (VSS) on the transmission. If the main ECU doesn't know the speed, it cannot broadcast it to the AC module.

2. 2

   Check for Accompanying Codes: Look for other CAN bus communication codes in the Engine or Transmission ECUs. If multiple modules are reporting missing data, the CAN bus network is compromised.

3. 3

   Inspect the AC Module Connector: Access the rear of the Climate Control Panel in the cab. Check the multi-pin connector for loose pins, backed-out wires, or corrosion.

4. 4

   Test CAN Bus Integrity: Using a multimeter, probe the CAN High and CAN Low pins at the AC module connector. You should see approximately 60 ohms of resistance across the network (with the battery disconnected).

1. 1

   Resolve Speed Sensor Issues First

   If the speedometer was dead during your diagnostic checks, locate the Vehicle Speed Sensor on the transmission housing. Inspect its wiring for damage (common in agricultural environments). Replace the sensor if it fails a continuity test.

2. 2

   Repair CAN Wiring

   If the speed sensor is fine but the CAN resistance at the AC module is out of spec (e.g., 120 ohms or open circuit), trace the CAN High and CAN Low wires from the AC module back to the main cab harness splice. Repair any chafed, broken, or rodent-damaged wires.

3. 3

   Clean Connections

   Apply a high-quality electrical contact cleaner to the AC module harness connector and reseat it firmly to ensure a good connection.

4. 4

   Replace or Repair the AC Module

   If the wiring is perfectly intact, the speed sensor works, and the code persists, the CAN transceiver inside the AC Module has likely failed. The Climate Control Panel will need to be replaced or sent out for circuit board repair.

5. 5

   Clear Codes

   After repairs, cycle the key and use a diagnostic tool to clear the inactive fault codes.