Troubleshooting & Status Lights
Generator Won't Start, Yellow Light, Red Alarm: Standby Generator Troubleshooting
What the status lights mean, what an overcrank alarm is telling you, and — just as important — which alarms you can safely reset yourself versus which ones need an authorized dealer. This is general guidance from manufacturer documentation.
In short
- On a Generac controller: green is ready and in AUTO, yellow is maintenance due or a non-critical warning (the unit still runs), red is OFF or an active shutdown alarm, and blue is service mode.
- Yellow is usually not an emergency. It most often means service is due, not that the generator has failed.
- Overcrank means the engine cranked and did not start. Generac documents causes including inadequate fuel pressure, a fuel shutoff valve left OFF, the wrong fuel selected in the controller, and a low battery.
- Kohler's RDC2 controller uses a different scheme entirely — flashing patterns on the OFF LED, not a colour code. Read the scheme for the controller you actually have.
What to confirm for your own home
- Your controller brand and model before matching any indicator — the colour schemes are not interchangeable.
- The exact alarm text or code shown on the display, and whether the unit is in AUTO.
- When the unit was last serviced, since a yellow maintenance state resolves with service rather than repair.
What this page does not do
It is not a repair manual and it will not tell you to open anything. A standby generator has both utility and generator power inside the enclosure; diagnosis beyond reading the display and checking the switch position is licensed electrical work.
What the Status Lights Mean
The light on the controller is the fastest read on what your generator is doing. Generac and Kohler use different schemes.
| Controller | Indicator | What it means |
|---|---|---|
| Generac | Green | Ready and in AUTO. Flashes while the generator is running during an outage. |
| Generac | Yellow | Maintenance due or a non-critical warning. The unit still runs. |
| Generac | Red | OFF, or a shutdown alarm is active. |
| Generac | Blue | Service mode (Next Gen controllers). |
| Kohler RDC2 | OFF LED on 2s, then flashing every 2s | Off, or the exercise cycle will not run. |
| Kohler RDC2 | OFF LED fast-flashing while in AUTO | A fault shutdown has occurred. |
The Yellow Light: Usually Not an Emergency
On a Generac, the yellow light is a maintenance reminder or a non-critical warning — it does not stop the generator. The unit will still start and run during an outage. Documented triggers include scheduled maintenance coming due, a battery check, and charger warnings.
It is a “take care of this soon” signal, not a “your generator is down” signal. A red light is the one that means the unit is OFF or has shut itself down.
“Won't Start” and the Overcrank Alarm
On a Generac, an OVERCRANK alarm (codes 1100 / 1101) means the engine cranked but did not start after five attempts. The manufacturer documents these common causes:
- Inadequate fuel pressure
- Fuel shutoff valve in the OFF position
- Wrong fuel selection set in the controller
- Air filter issue
- Improper installation
- Low battery
The manufacturer notes this list is not exhaustive— other faults can produce the same alarm. Work through the documented causes you can safely check (is the fuel shutoff valve open? is the controller set to the right fuel?), and if the unit still won't start, it's a dealer call.
Which Alarms You Can Reset — and Which Need a Dealer
Some alarms are owner-resettable — for example, a Generac Auxiliary Shutdown (code 2800). But engine-protection and electrical-fault shutdowns are not owner-resettable and require an authorized dealer. On Kohler, speed and frequency shutdowns direct the owner to a dealer as well. Once you know which class of fault you are looking at, the repair and service guide covers who is allowed to clear it and whether the repair is worth authorising.
A rule worth following
Per manufacturer guidance, never simply clear an alarm without correcting the underlying cause. An engine-protection shutdown fired for a reason; resetting it without fixing what tripped it can let real damage continue.
Before You Open a Panel
Everything here is general guidance drawn from manufacturer documentation. Reading a status light and checking a fuel valve is one thing; a specific repair is another. Specific repairs need an authorized dealer, and any warranty-covered work must be performed by a dealer to keep that coverage intact.
Deciding between brands before you buy? See our Generac vs. Kohler comparison, and for what an install actually costs, the cost guide.
Shopping for a standby generator?
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