Kohler generator code Voltage Low
Medium severity — Output voltage fell below about 80% of nominal for more than 10 seconds, most often from an overload or a failing regulator, so the controller shut the unit down.
Applies to: Kohler residential standby generators with an RDC2 or DC2 controller
What it means
Where Voltage High reacts in two seconds, Kohler gives Voltage Low a full ten-second window before shutting the engine down — output has to sit below about 80% of the system's nominal voltage that entire time, not just dip briefly, which is the controller's way of filtering out a momentary sag (say, from a big motor starting) from a genuinely sustained problem. Because voltage sag so commonly turns out to be a symptom of asking the generator for more than it can supply, this fault is usually the first sign that a connected load is heavier than the unit is rated for, rather than solid evidence of a failed part. That's a meaningfully different starting point than the overvoltage fault, where a regulator problem is almost always to blame.
Most common causes
The most common reasons output voltage sags this much:
- Generator loaded beyond its rated output
- Failing voltage regulator (AVR)
- Worn brushes or a weak rotor/stator
What you can check yourself
Check these before assuming the alternator itself has failed:
- Shed some connected load, particularly large motor loads, and retry
- Check for loose or corroded output wiring connections with the unit off
If the generator was carrying a genuinely modest load and voltage still sagged this far, that's a stronger signal of a regulator or winding problem than of simple overload.
All codes for this brand
Every Kohler generator fault code — full list with what differs between models.
Related codes: Voltage High and EngineSpeed Low. See the Overload or Nuisance Tripping symptom page for related causes.