Case IH 518502-00 - BCM – BCM: LIN Bus A - short to ground / Air conditioner clutch solenoid driver - too many loads or faulty load

There is a short to ground on the LIN Bus A communication network, or the AC clutch solenoid driver circuit is experiencing excessive current draw, an internal short circuit in the clutch coil, a failed engine harness, or a bad ground.

• MAGNUM AFS Connect
• Magnum 400 AFS Connect PIN HCCZ, Tier 3

1. 1

   Initial Harness Inspection: Turn the key switch OFF and disconnect the OEM harness from the air conditioner clutch or air conditioner clutch relay.

2. 2

   Pin and Connector Check: Inspect the air conditioner clutch connector and BCM harness for damaged pins, bent/broken pins, or corrosion.

3. 3

   Circuit Testing (Short to Ground): Use a digital voltmeter to check for open or short circuits in the wiring harness between the BCM and the AC clutch, as well as on the LIN Bus A network.

4. 4

   Power and Ground Test: With the engine running and the AC system turned on, use a digital voltmeter to check for power and ground at the compressor clutch connector. If there is 12 volts or more between the leads and the clutch is not engaged, the compressor's clutch or connector is bad.

5. 5

   Current Draw Test: Power the air conditioner clutch directly from the battery to check for excessive current draw or an internal short circuit.

6. 6

   Relay and Fuse Check: Verify that the AC clutch relay and the fuses in the power distribution box are intact and not blown due to the overload.

1. 1

   Disconnect Power

   Always disconnect the battery before servicing high-current fuses or electrical components to reduce the risk of electrical shock or ECU damage.

2. 2

   Repair Wiring/Pins

   If the diagnostic checks reveal damaged pins in the connectors, repair or replace the damaged pins. If the OEM harness has a short to ground (either on the LIN Bus A wire or the AC clutch supply circuit), repair the damaged section of the harness.

3. 3

   Replace the AC Clutch Coil

   If the direct-to-battery test shows that the AC clutch coil has an internal short circuit (which causes the ECU to shut down the driver due to excessive load), the clutch assembly must be replaced. On high-mileage compressors, replacing the compressor and clutch as a complete assembly may be more cost-effective.

4. 4

   Reassemble and Test

   Reconnect all harnesses, replace any blown relays or fuses, and reconnect the battery. Clear the fault codes from the BCM and run the AC system to verify the clutch engages without logging a driver overload fault.