Massey Ferguson 10.X.21 – AIRCON: Air Conditioning Compressor Relay Signal From AC Module Issue

The climate control system has detected an electrical fault (such as an open circuit, short to ground, or short to power) in the control circuit for the A/C compressor relay. Because of this signal failure, the module cannot successfully command the relay to close, which prevents the A/C compressor clutch from engaging and stops the air conditioning from cooling.

• 7724S
• 5712SL
• 7722
• 7722S
• 5713SL
• 7720S
• 7716
• 7718
• T4
• 7715
• 5710SL
• 7726
• 7726S
• 5711SL
• 7718S
• 7719
• 7714
• 7716S
• 7720
• Tier 4 (2015-2021)
• 7715S
• 7724
• 4700 Global Series
• 5700 Global Series
• 6700 Global Series
• 4707-4710
• 5710-5713
• 6711-6713
• 5600 Series
• 6600 Series
• 5608-5613
• 6612-6616
• 7600 Series
• 7700 Series
• 7614-7626
• 7714-7726
• 8600 Series
• 8650-8690

1. 1

   Perform a relay swap test by swapping the A/C compressor relay (often K3) with a known good relay of the same type to see if the compressor engages.

2. 2

   Use a multi-meter to verify that the proper voltage is reaching the relay socket from the AIRCON module.

3. 3

   Inspect the wiring harness between the AIRCON module, the relay panel, and the compressor clutch for any breaks, chafing, or melted insulation.

4. 4

   Test the resistance of the A/C compressor clutch coil at the compressor. A shorted clutch coil can draw excessive amperage and burn out the relay or damage the module's output circuit.

1. 1

   Power Down

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

2. 2

   Access the Relay Panel

   Open the main cab fuse/relay panel (location varies by model, typically in the right-hand console or the cab roof).

3. 3

   Inspect the Socket

   Remove the A/C compressor relay. Inspect the socket terminals for signs of heat damage, melting, or corrosion. Clean the contacts with electrical contact cleaner if necessary.

4. 4

   Replace the Relay

   If the relay failed the swap test or shows signs of internal failure, install a new OEM 12V relay.

5. 5

   Repair Wiring

   If the diagnostic checks revealed a broken wire between the AIRCON module and the relay, splice and heat-shrink the damaged section of the harness.

6. 6

   Reassemble and Test

   Reconnect the battery, start the tractor, and turn the A/C to maximum cooling. Verify that the compressor clutch "clicks" and engages.

7. 7

   Clear Codes

   Use the tractor's dashboard diagnostic menu or the AGCO Electronic Diagnostic Tool (EDT) to clear the inactive 10.X.21 fault code from the AIRCON module's memory.