Your Generac Guardian 22kW generator is built to be reliable. It’s designed to start automatically when the grid goes down and keep your home powered during outages. But what if it doesn’t?
👉 A generator that won’t start—or won’t stay running—can be a huge stress point, especially in the middle of a storm. The good news is that most issues are simple and preventable with routine checks. In fact, about 70% of failures come down to battery or maintenance neglect.
This guide gives you a step-by-step troubleshooting process so you can diagnose the problem quickly and know when it’s time to call in a pro.
⚡ Why Generators Fail to Start or Run Properly
Standby generators are engines, and like cars, they need the right balance of:
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Power (battery)
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Fuel (natural gas or propane)
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Lubrication & cooling (oil and coolant)
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Airflow (filters and exhaust clearance)
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Electronics (control panel and transfer switch)
When one of these systems isn’t working, the generator won’t start—or it may run poorly.
👉 Think of troubleshooting as checking each of these systems one by one.
🔗 Consumer Reports – Common Generator Problems
🔋 Step 1: Check the Battery
The battery is the #1 cause of generator startup failure. Without it, the engine simply can’t crank.
What to Do
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Open the generator panel and inspect the battery.
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Make sure cables are tight and free of corrosion.
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Use a multimeter to check voltage:
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A healthy 12V battery should read 12.6 volts or higher.
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Below 12.0V = weak battery.
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If the battery is older than 2–3 years, consider replacement.
Quick Fixes
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Clean corroded terminals with a baking soda/water solution.
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Charge the battery with a trickle charger.
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Replace if voltage won’t hold.
👉 If your generator clicks but won’t start, 9 times out of 10, it’s the battery.
🔗 Generac – Battery Maintenance Guide
⛽ Step 2: Verify Fuel Supply
Your generator can’t run without fuel. If the battery is fine, the next step is checking fuel supply.
For Natural Gas (NG) Systems
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Confirm your gas service is active.
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Make sure the gas meter is rated for generator use—some require an upgrade for higher flow rates.
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Inspect valves—sometimes they get shut off during service work.
For Propane (LP) Systems
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Check the tank level: standby generators often won’t run if below 25% full.
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Low propane can cause regulator freezing in cold weather.
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Inspect for leaks, damaged regulators, or blocked valves.
👉 Fuel issues are common after long outages—utilities may shut off gas lines, or propane tanks may simply run empty.
🔗 Propane.com – Generator Fuel Tips
🛢️ Step 3: Inspect Oil & Coolant Levels
Most Generac Guardian models have low oil sensors that prevent startup if levels are low—protecting the engine from damage.
What to Do
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Pull the dipstick and check oil level.
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If low, top off with Generac-approved synthetic oil.
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Check for leaks around the oil filter or seals.
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For liquid-cooled models, check coolant reservoir.
Warning Signs
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Fault code for “Low Oil Pressure.”
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Engine cranks but immediately shuts down.
👉 Never bypass oil sensors—they protect your $10K investment.
🔗 Energy.gov – Generator Maintenance Basics
🌬️ Step 4: Check Air Flow & Filters
Engines need air to breathe. If airflow is blocked, the generator may stall or refuse to start.
Steps to Check
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Remove the air filter and inspect for dirt, dust, or rodents.
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Replace filters every year or sooner in dusty climates.
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Clear snow, leaves, or debris from intake/exhaust vents.
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Make sure there’s 18 inches of clearance around the unit.
👉 A dirty air filter is a small problem that causes big headaches.
⚙️ Step 5: Review Control Panel & Error Codes
The Generac Guardian control panel is your troubleshooting best friend. It displays fault codes that point to the issue.
Common Fault Codes
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Overcrank: Engine failed to start after multiple attempts.
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Low Oil Pressure: Oil too low or sensor issue.
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Overspeed/Underspeed: Engine running outside safe RPM range.
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Overload: Too much demand on the generator.
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Undervoltage: Electrical issue preventing stable output.
👉 Clear minor codes by pressing “Enter” twice—but if the fault persists, call a pro.
🔗 Generac Owner’s Manual – Error Code Reference
🔌 Step 6: Test the Transfer Switch
Sometimes the generator runs fine—but your home stays dark. That’s usually the automatic transfer switch (ATS).
Quick Checks
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Look for tripped breakers inside the ATS.
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Inspect for burned wires or a tripped main breaker.
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Make sure the ATS is in “Auto” mode, not “Off.”
👉 If you’re not comfortable with electrical panels, stop here—call a certified technician.
🔗 Generac – Transfer Switch Basics
🛠️ When to Call a Professional
Some problems are DIY-friendly (battery, oil, air filter). Others require pro service:
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Fuel leaks or regulator failures.
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Persistent error codes that won’t clear.
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Transfer switch malfunctions.
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Engine knocking, smoke, or unusual vibrations.
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Wiring issues in the main service panel.
👉 If in doubt, call a certified Generac dealer—especially for fuel or electrical issues. Safety first.
🧰 Preventive Maintenance Tips
The best troubleshooting strategy is prevention. Here’s Savvy’s simple checklist:
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Run weekly self-tests (make sure they’re enabled).
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Check oil after long outages.
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Replace battery every 2–3 years.
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Change filters and spark plugs annually.
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Keep the area clear of snow, leaves, and clutter.
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Use the Mobile Link app for remote alerts.
👉 These habits prevent 90% of startup failures.
✅ Final Troubleshooting Checklist
If your generator isn’t starting or running right, work through this list:
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Battery 🔋 – Is it charged and corrosion-free?
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Fuel ⛽ – Is the tank full or utility supply active?
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Oil & Coolant 🛢️ – Are levels topped off?
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Airflow 🌬️ – Are filters clean and vents clear?
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Control Panel ⚙️ – What error code is showing?
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Transfer Switch 🔌 – Is power reaching the house?
👉 If all six check out and it still won’t run—it’s time to bring in a professional.
In the next topic we will know more about: Is a 22kW Generator the Right Size for Your Home?
