Generator keeps cutting out mid-cycle - faulty AVR or something else?

Had almost identical grief with my old Kipor 3kVA last winter — generator would chug along fine for twenty minutes then just die, sometimes with the lights flickering dramatically before it gave up the ghost.

Turned out to be a combination of things working against each other:

1. Dirty carburettor jets — partial blockage meant it couldn't sustain load under demand spikes
2. Worn AVR — the voltage was hunting badly before cutout, which I only spotted once I put a cheap multimeter on it

The AVR was the more dramatic culprit though. When it starts struggling, the output voltage goes all over the place and modern inverter-chargers like my Victron MultiPlus will disconnect themselves as a protection measure — looks like the genny dying but actually it's the inverter being sensible.

Before you splash out on a new AVR, worth checking:

• Is the cutout happening under load or at idle too?
• Have you cleaned the air filter and carb recently?
• What's actually tripping — the generator's own overload protection, or your downstream equipment?

If it's hunting at idle (revs rising and falling rhythmically), that's almost always the AVR or governor. If it cuts cleanly under heavy load, I'd suspect fuel delivery first.

What generator are you running and roughly how old is it? Makes a big difference — some of the older Chinese units have AVRs that are basically consumables after five or six years.

Anyone else been down this rabbit hole? Keen to hear whether others have had luck rebuilding AVRs versus just replacing them outright.

@SteveBurns99 that flickering before the cutout is the tell-tale sign — had exactly that on my boat's backup genny two winters ago. Turned out to be a failing AVR combined with a partially blocked fuel filter creating a lean-running condition. The AVR was struggling to compensate for the voltage fluctuation, then when the engine stumbled under load it just gave up entirely.

Worth checking in this order:

• Fuel filter first (cheap, often overlooked)
• AVR connections — corrosion on the terminals is brutal in damp conditions
• Brushes on the alternator head if it's a brushed type

Replacement AVRs for Kipors are about £15-20 on eBay — practically disposable. Fitted one myself with nothing more than a multimeter and a Sunday afternoon.

@SteveBurns99 @Del — worth checking the capacitor on the AVR before condemning the whole unit. On my old Stephill 6kVA I had near-identical symptoms: run fine for 15-20 mins then voltage collapse with that pre-death flicker. Turned out the capacitor was drifting badly once heat-soaked — dead cheap fix, under a fiver.

Also worth ruling out:

• Fuel starvation — partially blocked carb jet that only manifests under sustained load
• Dirty air filter causing richening at temperature

If you've got a multimeter, log output voltage every few minutes during a run cycle. You'll likely see it creeping down before the cutout — that pattern tells you AVR/capacitor rather than fuel/air. Kipor parts are still findable on eBay if it does turn out to be the AVR board itself.

@VivaroWanderer the capacitor angle is worth pursuing, but I'd also rule out fuel starvation before pulling the AVR apart — classic symptom of a partially blocked carburettor needle valve or gunked-up fuel filter is exactly that 20-minute run-then-die pattern, because the engine runs down whatever fuel is sitting in the float bowl, then starves.

On my cabin's backup genny I chased an AVR fault for two weekends before realising the petrol had gone off over summer and was leaving varnish deposits throughout the carb. Full strip, ultrasonic clean, fresh fuel, problem gone.

Sequence I'd follow:

1. Fresh fuel + inline filter inspection
2. Carb float bowl check
3. Then capacitor/AVR

Saves condemning good components. If the flickering is voltage instability rather than frequency drop, that's when I'd point firmly at AVR or brushes.

@QMC_Camper good shout on fuel starvation — had something similar on a little Honda EU22i I borrowed for my garden office build last year. Turned out the fuel cap vent was partially blocked, creating a vacuum in the tank as it ran. Generator would die after roughly the same interval every time, almost like clockwork.

Easy test: next time it's running and you feel it starting to labour, crack the fuel cap slightly. If it immediately recovers, that's your answer right there.

Obviously worth ruling out before spending money on AVR components. What's the ambient temperature been like when it cuts out? I've also read that some generators run lean in colder air and the carb needle needs adjusting seasonally — not sure if that applies to your specific unit though.

@GeorgeJohnson83 one thing nobody's mentioned yet — thermal cutout. On the Kipor units especially, the overload protection bimetal strip gets weak with age and starts tripping at well below its rated threshold. Twenty-minute runtime before shutdown is a classic sign; the engine's warmed the strip enough to trip it even under a modest load.

Before touching the AVR or fuel system, check what load you're actually pulling versus the generator's rated output. Kipor's "3kVA" rating is optimistic at best. I ran one on my boat for two seasons and found it struggled above about 2.2kW in practice.

Also worth checking: is the shutdown clean or does it splutter out? Clean cutoff points toward electrical protection. Spluttering and dying suggests @QMC_Camper's fuel starvation route is more likely.