Generator runs fine but stalls or bogs when load is added

Symptoms

• Runs fine unloaded, bogs down or stalls with anything plugged in
• Engine sounds like it's straining right when a device is plugged in
• Lights dim severely when a load is added
• Breaker trips as soon as load is applied

Likely causes

• CommonConnected load exceeds the generator's rated wattageEspecially with motor-driven appliances that draw a large surge at startup.
• PossibleWeak or degrading engine output (compression or fuel issue)An engine that's already running at reduced power can't handle even a normal load.
• PossibleFailing AVR (automatic voltage regulator)A failing AVR can cause the generator to bog excessively or stall as soon as demand increases.
• Less commonLoose or corroded wiring inside the generator headPoor connections can cause excessive voltage drop under load.

What to do

1. Check the wattage rating of the generator against the running and startup wattage of what you're plugging in.
2. Start with the smallest, lowest-wattage device first to see whether the generator handles a light load acceptably.
3. If even a light load causes bogging, suspect an engine performance issue rather than an overload; check fuel and air filter first.
4. Inspect the fuel and air filter, since a starved or choked engine has less reserve power to handle load.
5. If the engine sounds strong but voltage/lights still sag heavily under load, the AVR may be failing.
6. Try the generator's built-in outlets one at a time to see if the problem is isolated to a specific circuit.
7. If a healthy engine still can't handle rated load without stalling, have a generator repair shop test the AVR and generator head.

Tools and parts

• None required for basic checks

When to call a pro

If the generator can't handle even modest rated load despite good fuel and air supply, have the AVR and generator head tested by a repair shop.

Safety