Why Does My RV Generator Shut Down Under Load?
A generator that idles happily in the driveway and dies the moment the air conditioner starts has a capacity problem, not a starting problem.
What's actually happening
An unloaded generator is barely working. Ask it to run a rooftop air conditioner and the engine has to produce real power immediately — and the compressor's inrush demand is higher still for the first moment.
That step change is what exposes weaknesses. Fuel delivery that is adequate at low demand may not be adequate at high demand. Governing that looks fine unloaded may not hold speed under load. Output faults that never appear without current flowing show up immediately once it does.
When customers notice it
- The air conditioner starts and the generator bogs, surges or quits
- The microwave runs for a moment and the unit shuts down
- Two appliances together are fine, three are not
- The unit runs unloaded indefinitely but cannot sustain real household load
Possible categories
Fuel delivery
Restricted filters, weak pump output, or supply problems that are only revealed when consumption increases.
Carburetion and fuel metering
The high-demand circuits of a carburetor are separate from the ones used at light load. A unit can run cleanly unloaded and still be unable to meter enough fuel under load.
Governor and engine speed control
Speed control has to react to the load. Governing problems typically show up as bogging, hunting or a shutdown at the moment load is applied.
Generator output and excitation
Faults on the electrical side can cause the controller to shut the unit down on out-of-range voltage or frequency even when the engine is running.
Electrical faults and wiring
Loose connections and marginal grounds can behave normally at low current and fail as current rises.
Genuine overload
Some shutdowns are the generator working correctly. A unit sized for one air conditioner will not carry two plus a water heater. Total connected load is worth confirming before assuming a fault.
Maintenance and heat
Restricted air flow, dirty air filters, deferred service and cooling problems all matter more under load, because that's when the engine is producing heat.
Why load testing is essential
This is the category of failure that cannot be diagnosed by starting the generator and listening to it. Some failures only appear when the unit is actually producing significant power, so the diagnosis has to reproduce that.
Applying a controlled load and observing engine speed, output and shutdown behavior is what separates an actual diagnosis from a guess — and it is a routine part of how we approach these calls.
Generator diagnosis can involve fuel, high temperatures, electrical power, and carbon-monoxide hazards. If you're not equipped to perform the testing safely, have the generator professionally diagnosed.
Generator diagnosis can involve fuel, high temperatures, electrical power, and carbon-monoxide hazards. If you're not equipped to perform the testing safely, have the generator professionally diagnosed.
Frequently asked questions
- Why does my generator shut off when the air conditioner starts?
- The step increase in demand exposes weaknesses in fuel delivery, fuel metering, governing or electrical output that aren't visible when the unit runs unloaded. Genuine overload is also possible if total connected load exceeds the unit's rating.
- Can a generator run fine and still have a real fault?
- Yes. Running unloaded requires very little of the machine. Load testing is what reveals faults that only appear when the generator is producing significant power.
- Is it overload or a failure?
- That depends on the unit's rating and what is actually switched on. Confirming total load is part of the diagnosis, because a correctly working generator protecting itself from overload is not a repair.
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RV generator problems can have several different causes that produce nearly identical symptoms. No Worries RV can diagnose the system at your RV and explain the repair options before the work proceeds.
Mobile RV generator repair throughout the Tampa Bay area