Massey Ferguson 27 – Air Conditioning Module (AIRCON): Issue With Signal To Left Cab Fan Speed Controller (AIRCON)

Fan speed controller no. 1 output error where the electrical signal is outside of its expected operating range. This indicates the controller is either receiving an improper voltage/ground signal, or the component itself has failed internally and is not returning the correct feedback.

• 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
• 8690
• 7600 Series
• 7700 Series
• 7614-7626
• 7714-7726
• Global Series
• 4700 Series
• 5600 Series
• 5700 Series
• 6600 Series
• 6700 Series

1. 1

   Inspect the wiring harness from the AIRCON module to the left cab fan speed controller for chafed wires, pinched lines in the cab roof, or melted insulation.

2. 2

   Disconnect the plug at the fan speed controller and inspect the pins for corrosion, moisture ingress, or signs of arcing/melting.

3. 3

   Test the blower motor by manually spinning the left cab fan to ensure bearings are smooth. Test the motor's current draw to ensure it is not pulling excessive amperage, which can burn out the controller.

4. 4

   Verify the AIRCON module is receiving proper supply voltage to rule out undervoltage or overvoltage conditions.

1. 1

   Power Down

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

2. 2

   Access the HVAC Unit

   Remove the interior cab roof liner or the exterior roof hatch (depending on your specific model's access panel) to expose the blower motors and HVAC housing.

3. 3

   Locate the Controller

   Locate the left-side blower motor assembly. The fan speed controller (resistor block) is typically mounted directly into the HVAC ductwork next to the fan so that the airflow can cool its heat sinks.

4. 4

   Remove the Faulty Unit

   Disconnect the multi-pin electrical connector from the controller. Remove the retaining screws and pull the controller out of the duct.

5. 5

   Install the New Part

   Insert the new speed controller into the housing, secure the screws, and firmly seat the electrical connector.

6. 6

   Test

   Reconnect the battery. Turn the ignition on and test the HVAC fan manually through all speed settings to ensure the left fan responds correctly.

7. 7

   Reassemble and Clear Codes

   Reinstall the cab roof panels. Use an AGCO Electronic Diagnostic Tool (EDT) or the tractor's onboard diagnostic menu to clear the inactive fault code 27.