Massey Ferguson 31 – AIRCON: Issue With Signal To Left Cab Fan Speed Controller (AIRCON)

The input signal from the fan speed controller (potentiometer or switch) is outside of its normal operating range. This is typically caused by a short circuit to earth or an open circuit in the switch, resistor, or wiring harness.

• 7724S
• Interim Tier 4 (2012-2015)
• 7722S
• 7722
• 7615
• 7720S
• 7716
• 7718
• 7726
• 7715
• 7616
• 7618
• 7619
• 7626
• 7624
• 7726S
• 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

   Test the voltage and resistance signal coming from the left cab fan speed controller (potentiometer/switch) to ensure it is within the operating range.

2. 2

   Inspect the wiring harness between the fan speed switch, the blower motor resistor, and the AIRCON module for an open circuit or a short circuit to earth.

3. 3

   Test the cab fan resistor regulator and the 3-position fan control rocker switch for burnt electrical contacts or internal faults.

1. 1

   Access the dash panel or headliner console where the fan speed switch is mounted.

2. 2

   Carefully remove the panel to expose the rear of the switch.

3. 3

   Take a quick photo of the wire connections (typically a 5-spade connection) before disconnecting them to ensure correct reassembly.

4. 4

   Disconnect the wiring harness from the switch.

5. 5

   Pop the old switch out of its housing and install the direct replacement factory switch.

6. 6

   Reconnect the wires according to your reference photo and test the fan on all three speeds (low, high, off) before reinstalling the dash panel.