Alternator Loss of Field or Excitation Fault

Common Symptoms

• Generator starts and runs but produces little or no AC output voltage
• Panel displays fault code 32 and generator shuts down shortly after cranking
• Lights or appliances connected to the generator flicker briefly then go dark
• READY light goes out and a red fault light comes on after an attempted start
• Weekly exercise cycle starts the engine but the unit shuts down before completing the run
• Generator cranks and fires normally but the ATS never transfers the load to the generator
• AC voltmeter on the panel reads zero or well below normal when engine is running

Probable Causes (Ranked by Likelihood)

• Failed or out-of-adjustment AVR (automatic voltage regulator) not supplying field excitation current Very Likely
• Worn, stuck, or broken brushes preventing current from reaching the rotor field winding Very Likely
• Open or shorted rotor field winding inside the alternator Likely
• Residual magnetism lost in the rotor, preventing self-excitation on startup Likely
• Broken or corroded wiring in the excitation circuit between the AVR and the brush assembly Possible
• Faulty RDC2 controller misreading field feedback and triggering a false Code 32 shutdown Possible
• Shorted or open stator excitation winding supplying the AVR Less Likely

Step-by-Step Diagnostic Procedure

1. Start safely. Set the panel switch to OFF. Disconnect the generator from any load and make sure the ATS or MTS is in utility position before you begin any inspection.

2. Check the brush assembly first. On most Kohler RES and RCL units, the brush holder is accessible from the rear of the alternator end cap. With the unit OFF and cool, inspect brushes for length (replace if worn below 0.25 inches), free movement in the holder, and signs of burning or cracking. This is the single most common fix for Code 32.

3. Measure brush spring pressure by feel. Brushes should seat firmly against the slip rings. Clean the slip rings with a lint-free cloth. Look for scoring, pitting, or a heavy black glaze, all of which increase resistance and starve the field of excitation current.

4. Inspect AVR wiring. With the panel in OFF, locate the AVR module (typically mounted on the alternator or inside the control panel). Look for burnt connectors, loose terminals, or wires that have rubbed through insulation. Wiggle each connector and look for corrosion on the pins.

5. Flash the field if residual magnetism is suspected. With the engine running at no-load speed, briefly apply 12 V DC from the generator's starting battery across the field terminals (F+ and F-) for two to three seconds, observing polarity. If AC output voltage appears and then collapses when you remove the battery leads, the AVR is likely the problem. This step requires a wiring diagram, so call a technician if you are not comfortable working near running equipment.

6. Measure rotor field resistance. With the unit OFF and the brushes lifted away from the slip rings, use a multimeter set to ohms and measure resistance across the two slip rings. Most Kohler residential alternator rotors read between 15 and 60 ohms depending on model. A reading of zero (shorted) or OL (open) means the rotor field winding has failed and the alternator must be rebuilt or replaced. This requires a technician.

7. Check for RDC2 controller faults. Navigate the RDC2 controller display panel to the fault history menu. If Code 32 appears alongside codes for under-voltage (Code 14) or over-speed (Code 13), the root cause may be a cascade failure rather than the field circuit alone. Note all stored codes before clearing.

8. If brushes and wiring check out, replace the AVR. The AVR is a plug-in module on most Kohler RES and RCL units. Kohler part numbers vary by kW rating, so match your model exactly. If replacing the AVR does not restore output, the fault is inside the alternator and requires a qualified technician with a growler or winding tester.

Frequently Asked Questions