If you’re seeing blinking lights or error codes on your golf cart’s SEPEX controller, you’re not alone. SEPEX (Separately Excited) controllers are smart and efficient, but they can also shut down or enter fault mode when something goes wrong. This guide breaks down the most common SEPEX controller fault codes and what to do about them.
Don’t jump straight to replacement. If your cart runs weak or not at all, the issue may be your battery pack. Try this DIY battery reconditioning course before spending hundreds on new parts.
What Is a SEPEX Controller?
SEPEX (Separately Excited) controllers are used in electric golf carts like Club Car, EZGO, and Yamaha. They allow separate control of the motor’s armature and field circuits, resulting in better speed regulation, regenerative braking, and programmable features.
How to Read SEPEX Controller Fault Codes
Most SEPEX controllers (like Curtis or Alltrax) use a flashing LED or diagnostic software to indicate error codes. The blink pattern tells you what system has failed—such as the throttle, motor, battery, or controller itself.
Common SEPEX Controller Fault Codes
| Fault Code | Issue | Likely Cause | Fix |
|---|---|---|---|
| 1-1 | Throttle Fault | Incorrect throttle signal | Check throttle wiring and settings |
| 1-2 | Battery Undervoltage | Low pack voltage | Charge or recondition batteries |
| 2-1 | Stuck Throttle | Pedal not at zero during start-up | Release pedal, recalibrate throttle |
| 2-2 | Field Open | Field wire disconnected or broken | Inspect motor wiring |
| 3-2 | Overtemperature | Controller too hot | Let cool, improve ventilation |
| 4-1 | Pre-charge Fault | Bad resistor or solenoid issue | Test pre-charge resistor (should be ~200–300 ohms) |
| 4-3 | Overvoltage | Battery voltage too high | Check battery bank for incorrect setup |
| 5-1 | Motor Stall | Locked rotor or high resistance | Inspect motor for binding or bad bearings |
| 6-1 | EEPROM Error | Internal controller memory fault | Reset or reprogram controller; may need replacement |
How to Reset a SEPEX Controller
- Turn off the cart and remove the key
- Set the tow/run switch to TOW
- Disconnect the battery pack’s main negative cable
- Wait 5–10 minutes
- Reconnect and set switch back to RUN
- Try again and listen for diagnostic beeps or LED flashes
Battery Voltage and Controller Health
Many SEPEX controller faults are caused by poor battery voltage. If your voltage drops under 36V (for a 36V system) or 48V (for a 48V system), the controller will either shut down or throw undervoltage errors.
Don’t waste money replacing batteries yet—recondition them at home using this method to improve range and power.
When to Replace the Controller
Only replace your SEPEX controller if:
- You’ve ruled out wiring, throttle, and battery issues
- The controller won’t reset and still flashes memory fault codes
- You’ve used diagnostic software and confirmed internal error
Controllers can cost $300–$600. Avoid replacements unless all other components are verified.
Preventing SEPEX Faults
- Keep batteries charged and clean
- Don’t store the cart with low voltage
- Keep connections tight and corrosion-free
- Ventilate the controller area to reduce overheating
- Use correct throttle settings and check programming with diagnostic tools
Conclusion
SEPEX controller fault codes may look intimidating, but once you understand the blink patterns, it’s easy to figure out what’s wrong. Most issues can be fixed without replacing the controller.
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