John Deere 000158.00 – FCC / RLC / CLC / PTQ: Regulated Voltage Above 18V

The system has detected that the regulated voltage is above 18 volts. This points to a problem within the machine's charging system, which is creating an overcharge condition. A properly functioning charging system should maintain a voltage between approximately 13.5 and 14.5 volts while the engine is running. An overcharge condition can damage the batteries and sensitive electronic components.

• 7400A TerrainCut Mower
• 7200A Mower
• 7500A Mower
• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 6110M
• 6120M
• 6130M
• 6145M
• 6155M
• 6175M
• 6195M
• 7630
• 7730
• 7830
• 7930
• 7720
• 7820
• 7920
• 7810
• 7200
• 7400
• 7600
• 7460 Cotton Stripper

1. 1

   Visually inspect the alternator, batteries, and all related wiring for any visible signs of damage, corrosion, debris accumulation, or loose connections.

2. 2

   Restart the machine to see if the diagnostic trouble code reappears, ruling out a temporary glitch.

3. 3

   Perform a Battery Voltage Test (Engine Off): Measure the battery voltage at the terminals with a multimeter. A fully charged battery should read approximately 12.6 volts.

4. 4

   Perform a Charging System Voltage Test (Engine Running): Run the engine at around 1500 RPM and measure voltage across the battery terminals. It should be between 13.5 and 14.5 volts. A reading above 18V confirms an overcharging issue, likely due to a faulty voltage regulator.

5. 5

   Perform an Alternator AC Ripple Test: With the engine running, measure AC voltage between the alternator's main output post and a good ground. A reading higher than 0.5 volts suggests damaged diodes within the alternator.

6. 6

   Perform a Voltage Drop Test: Measure the voltage between the alternator's output terminal and the positive battery terminal while the engine is running. The voltage drop should be less than 0.5 volts.

1. 1

   Disconnect battery

   Disconnect the negative battery cable to prevent electrical shorts.

2. 2

   Access alternator

   Remove any necessary panels or shields to gain access to the alternator.

3. 3

   Remove drive belt

   Loosen the tensioner for the alternator belt and remove the belt from the alternator pulley.

4. 4

   Disconnect wiring

   Disconnect the electrical connectors and the main power wire from the back of the alternator.

5. 5

   Remove alternator

   Unbolt the alternator from its mounting brackets and remove it from the machine.

6. 6

   Install new alternator

   Mount the new alternator and tighten the mounting bolts.

7. 7

   Reconnect wiring

   Attach the electrical connectors and the main power wire to the new alternator.

8. 8

   Reinstall drive belt

   Place the belt back on the pulley and apply the correct tension.

9. 9

   Reconnect battery

   Reconnect the negative battery cable.

10. 10

    Verify repair

    Start the engine and perform the Charging System Voltage Test again to ensure the voltage is within the correct range (13.5 to 14.5 volts).