Massey Ferguson 24 – Air Conditioning Module (AIRCON): No Engine Speed Information Received On The CAN BUS To AC Module (AIRCON)

The AC module stopped receiving vital engine speed data broadcasted over the CAN bus from the Engine ECU, which is required to safely engage and disengage the AC compressor clutch.

• 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
• 8600 Series
• 8650
• 8660
• 8670
• 8680
• 8690
• 7600 Series
• 6700S Series

1. 1

   Check for accompanying codes (such as U 2857 CAN Bus Off or U 2859 CAN Frame Error) to determine if there is a network-wide CAN bus failure rather than an isolated AC module issue.

2. 2

   Verify the engine speed sensor is functioning and the Engine ECU is reading engine speed (typically 850-950 rpm at idle). If the primary sensor fails, the ECU cannot broadcast the data.

3. 3

   Inspect the CAN High and CAN Low communication lines between the Engine ECU and the AC Module for continuity, shorts to ground, or open circuits.

4. 4

   Inspect the multi-pin connectors at the rear of the Climate Control Panel/AC Module for backed-out pins, corrosion, or moisture ingress.

1. 1

   Power Down

   Disconnect the tractor's battery isolator switch before servicing the CAN bus or sensitive modules.

2. 2

   Harness Repair

   If the diagnostic checks reveal an open or shorted CAN wire between the Engine ECU and the cab roof/console where the AC module resides, locate the break and splice in a repair wire using weather-sealed connectors.

3. 3

   Connector Maintenance

   Clean the AC module harness connectors with electrical contact cleaner and apply dielectric grease. Re-seat the connector firmly.

4. 4

   Module Replacement/Repair

   If the wiring harness tests perfectly and the Engine ECU is confirmed to be broadcasting engine speed, the CAN transceiver inside the AC Module has likely failed. You must remove the Climate Control Panel from the cab and either replace it with a new OEM unit or send it out for remanufacturing.

5. 5

   Clear Codes

   Reconnect the battery, turn the key to the ON position, and use a diagnostic service tool (EST) to clear the inactive fault codes. Start the engine and verify the AC compressor engages.