Battery Charging Voltage Above Safe Upper Limit

Common Symptoms

• Sullair WS Controller LCD displays E011 on the side panel
• Yellow or red fault indicator light illuminates on the control panel
• Compressor may continue running but posts an active fault in the controller log
• Battery feels hot to the touch or you notice a rotten-egg sulfur smell near it
• Headlights or panel lights appear brighter than normal
• Battery swells, leaks, or shows visible corrosion at the terminals
• Repeated battery failures or shortened battery life on the unit

Probable Causes (Ranked by Likelihood)

• Faulty alternator voltage regulator holding output too high, typically above 15V DC on a 12V system Very Likely
• Failed or shorted alternator diode pack causing unregulated DC output Likely
• Loose or corroded alternator ground connection creating a false high-voltage reading at the controller Likely
• Damaged or incorrect alternator installed during a prior repair not matched to the engine OEM spec Possible
• Wiring fault or chafed wire between the alternator B+ output and the WS Controller sense input Possible
• WS Controller battery voltage sense input calibration drift or failed sense circuit on older units Less Likely
• Faulty battery with an internal short causing voltage to appear elevated to the controller Less Likely

Step-by-Step Diagnostic Procedure

1. Start with a visual check. Open the battery compartment and inspect the battery case for swelling, cracks, or electrolyte leakage. Check both terminals for heavy corrosion. A corroded positive terminal can cause false voltage readings at the WS Controller.

2. With the engine OFF, measure battery resting voltage across the terminals with a DC multimeter. A healthy 12V battery should read between 12.4V and 12.8V. A reading above 13.0V at rest suggests a recent overcharge event.

3. Start the engine and let it reach normal operating RPM (typically 1800 RPM or rated speed for the unit). Measure DC voltage at the battery terminals again. Normal alternator output should be between 13.8V and 14.4V DC. A reading at or above 15.0V DC confirms the alternator or its regulator is overcharging.

4. Move your multimeter leads directly to the alternator B+ output terminal and the alternator case ground. Compare this reading to the battery terminal reading. More than 0.5V difference between the two points signals a wiring or connection problem rather than a bad alternator.

5. Inspect the alternator ground strap. Trace it from the alternator case to the engine block or chassis. Tug on it firmly. Loose grounds are one of the most common causes of erratic voltage readings on towable units that move around job sites.

6. Check the small alternator sense wire (usually a separate thin wire at the alternator connector, not the main B+ cable). Corrosion or a broken connection on the sense wire causes the regulator to demand more output because it thinks charging voltage is low. Clean the connector with electrical contact cleaner and retest.

7. If alternator output is confirmed high (above 14.8V DC at the battery under load) and grounds and sense wiring are clean, the alternator voltage regulator is likely the cause. On most John Deere and Cummins engines in these units the regulator is internal to the alternator and requires alternator replacement or a rebuilt unit. Flag this for a service tech if you are not comfortable with alternator replacement.

8. For engine-side fault codes that may accompany E011, connect JD Service Advisor, CAT ET, or Cummins INSITE depending on your engine to check for any charging system DTCs logged at the ECM level before clearing the E011 from the WS Controller.

Frequently Asked Questions