Case IH 3659 – ENGINE: Power Supply Voltage: Out of Voltage - High

The Engine Control Unit (ECU) is detecting an incoming battery/charging voltage that exceeds the maximum safe operating threshold. When this occurs, the system may disable power stage diagnostics to protect the ECU and other sensitive electronic components from high-voltage damage.

• skid steer
• SR130
• SR160
• SR175
• SR200
• SR210
• SR220
• SR240
• SR250
• SV185
• SV250
• SV300
• TR270
• TR320
• TV380
• Farmall 95A
• Farmall 95U
• Farmall 105U
• Farmall 115A
• Maxxum
• Puma

1. 1

   Perform a static battery test with the engine off to ensure voltage at the battery terminals is approximately 12.6 volts.

2. 2

   Perform a running charging test by starting the engine and measuring voltage at the battery terminals. If voltage climbs rapidly above 14.5V–15.0V, the alternator is overcharging.

3. 3

   Inspect the wiring harness and engine grounds between the alternator, battery, and Engine ECU for loose, broken, or corroded connections that can cause the voltage regulator to overcompensate.

4. 4

   Perform an ECU pin voltage drop test directly at the EDC/ECU harness to confirm the high voltage is reaching the module and is not a false reading caused by a short circuit.

1. 1

   Disconnect Power

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

2. 2

   Access the Alternator

   Locate the alternator on the engine block. Remove the serpentine/fan belt by releasing tension from the automatic tensioner.

3. 3

   Remove the Alternator

   Disconnect the electrical connectors (B+ terminal and regulator plug) from the rear of the alternator. Remove the mounting bolts and extract the alternator.

4. 4

   Replace Components

   Depending on the model, you can either replace the internal voltage regulator on the back of the alternator or replace the entire alternator assembly (recommended if the unit has high hours).

5. 5

   Reinstall

   Mount the new alternator, torque the bolts to OEM spec, reconnect the electrical terminals, and reinstall the drive belt.

6. 6

   Battery Check

   Inspect the battery for bulging or acid leaks. Replace the battery if it was damaged by the overcharging state.

7. 7

   Clear Codes

   Reconnect the battery, start the engine, and verify the charging voltage is now stable (around 13.5V–14.5V). Clear the 3659 fault code using a diagnostic scan tool.