John Deere 000876.04 – ETC: A/C Compressor Clutch Low Voltage

The air conditioning compressor clutch is receiving insufficient voltage to engage properly. The clutch is an electromagnetic component that locks the compressor pulley to the internal shaft to pump refrigerant. Low voltage prevents the magnetic field from being strong enough to engage the clutch, causing it to slip, generate excessive heat, and potentially lead to premature failure of the clutch coil and a failure of the A/C system to cool.

• 4020
• 4320
• 4520
• 4620
• 5020
• 6030
• 7020
• 7520
• 4650
• 6110R
• 6120R
• 6130R
• 6R Series
• 7800
• 8330
• 8R Series
• 5225
• 5325
• 5425
• 5525
• 5625
• 6215
• 6415
• 6615
• 6715
• 6020
• 6120
• 6220
• 6320
• 6420
• 6520
• 6620
• 6820
• 6920
• 700J

1. 1

   Check battery and charging system to ensure batteries are fully charged and the alternator is functioning correctly (running voltage should be approximately 1.5V higher than resting voltage).

2. 2

   Inspect A/C system fuses and relays. Swap the A/C clutch relay with an identical one (e.g., horn relay) to test engagement.

3. 3

   Check refrigerant pressure. Low levels will cause the low-pressure switch (often located under the instructional seat) to open the circuit.

4. 4

   Test for voltage at the compressor clutch connector with the A/C turned on. If 12V or more is present but it doesn't engage, suspect the clutch coil or a bad ground. If 9-11V is present, suspect upstream wiring or components.

5. 5

   Temporarily bypass the low-pressure switch with a jumper wire to see if the clutch engages, which would indicate a faulty switch or low refrigerant.

6. 6

   Inspect all wiring and connectors between cab switches (blower, temperature, pressure) and the compressor for corrosion, pest damage, or loose connections.

1. 1

   Confirm the Cause

   Based on the diagnostic checks, identify the faulty component.

2. 2

   Address general voltage drop

   If diagnosing a general voltage drop due to long wire runs or high resistance in switches, install a 'clutch saver' kit or an additional relay close to the compressor to provide a direct 12V source.

3. 3

   Replace faulty fuses or relays

   If a fuse is blown, replace it with one of the same amperage. Replace any faulty relays identified during testing.

4. 4

   Replace faulty cab switches

   If the blower or temperature switch is not providing proper voltage, access the cab's control panel and replace the faulty switch.

5. 5

   Replace A/C pressure switch

   If the pressure switch is faulty, safely depressurize the A/C system before removing and replacing the switch.

6. 6

   Replace compressor clutch coil or assembly

   If the coil has incorrect resistance or has failed, replace the clutch coil. If necessary, replace the entire compressor assembly.

7. 7

   Repair wiring

   Repair or replace any damaged wiring sections found during inspection, ensuring all connections are clean and secure.

8. 8

   Evacuate and recharge A/C system

   If the system was opened to replace a pressure switch or compressor, properly evacuate and recharge it with the correct type and amount of refrigerant (e.g., R134a).