John Deere 158.04 – ATC / RLC: Switched Supply Voltage Low

The control unit has detected that the switched battery supply voltage feeding it has dropped below 9.0 Volts.

• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• S-Series Combines
• S670

1. 1

   Visually inspect around the batteries and alternator for any signs of damage, loose connections, or accumulated debris

2. 2

   Check the machine's overall charging system to ensure the alternator is outputting proper voltage (typically 13.5V - 14.4V) and the batteries are holding a charge

3. 3

   Verify the voltage at the relays and the fuse box (specifically the Cab Load Center wake-up circuit)

4. 4

   Disconnect the connector at the ATC/RLC roof module and measure the voltage on the switched power pins. If below 9V but battery is 12V+, suspect high resistance, a failing relay, or a chafed wire

1. 1

   Power Down

   Turn off the engine and remove the key. Inspect and clean the main battery terminals to rule out a primary ground or supply issue.

2. 2

   Check Fuses and Relays

   Locate the Cab Load Center (fuse panel). Identify the specific fuse and relay responsible for providing switched power to the ATC/RLC roof module.

3. 3

   Test the Relay

   Remove the relay and test for continuity and resistance. A failing relay can cause a voltage drop across its internal contacts. Replace the relay if it shows high resistance or fails to switch cleanly.

4. 4

   Inspect the Harness

   Trace the wiring harness from the cab load center up to the roof module. Look for pinch points, chafing, or damaged connectors that could cause a partial short to ground or high resistance.

5. 5

   Repair Wiring

   Repair any damaged wires or replace corroded connector pins at the roof module plug.

6. 6

   Cycle Power

   Reconnect the module. Turn the key switch on to cycle tractor power. Many John Deere voltage codes will correct themselves and clear simply by cycling the key switch once the underlying voltage drop is resolved.