Standby generators make noise—it’s unavoidable. But not all generator sounds are the same, and knowing the difference between normal operation and a warning sign can save you from a costly repair or a failed startup during an outage. Here’s a practical guide to understanding what you’re hearing from your generator.
Normal Generator Sounds
A steady engine hum: This is the baseline sound of a generator running at its operating RPM. It should be consistent and relatively smooth. Modern Kohler and Cummins generators are designed to run quietly, especially in residential enclosures.
A brief startup rattle: During the first few seconds after startup, some light mechanical noise is normal as oil circulates and the engine reaches operating temperature. This should settle quickly.
Click or relay sound during transfer: When the automatic transfer switch activates and connects the generator to your home, you may hear a mechanical click or relay sound from the transfer switch enclosure. This is normal and expected.
Sounds That Warrant a Service Call
Knocking or rattling: A persistent knocking sound from the engine can indicate low oil, a worn bearing, or loose internal components. Don’t ignore it.
Squealing or high-pitched whining: This may point to a slipping belt, a failing alternator bearing, or a cooling fan issue.
Backfiring: A loud bang or backfire during startup or operation is a sign of a fuel or ignition issue that needs professional attention.
Excessive vibration: If the generator is shaking more than usual, check whether it’s still properly secured to its mounting pad. Loose mounting hardware or a shifted pad can cause increased vibration that stresses components over time.
A change in engine speed: Your generator should run at a consistent speed. If it’s surging—speeding up and slowing down rhythmically—that indicates a fuel delivery or governor issue.
When in Doubt, Call
If your generator sounds different than it used to, trust your instincts. Contact Pow’r Point and describe what you’re hearing. Our technicians can often narrow down the cause over the phone and advise whether it’s urgent or can wait for a scheduled visit.
