Generac generator troubleshooting starts with one question: is the light yellow or red? A yellow light is usually something you can deal with yourself. A red light means the generator has shut down to protect itself, and you may need a dealer if it comes back after one reset.
This guide walks you through both. It covers Generac home standby generators and Generac portable generators, using the steps Generac publishes on its own support site. You will learn what each light means, what the common error codes are telling you, how to clear an alarm safely, and where the do-it-yourself part ends.
We have not repaired these generators ourselves. Everything here is taken from Generac’s official support articles, and we tell you when to stop and call a professional.
Generac troubleshooting at a glance
Read the light, read the code, then decide
Based on Generac’s official support articles for home standby and portable generators, checked in October 2026.
Quick answer
On a Generac home standby generator, a yellow light means a warning or a maintenance reminder, and the generator should still run in an outage. A red light means an alarm has shut it down. Find the code on the control panel or in the Mobile Link app, fix the cause if you can, clear the alarm once and try a manual start. If the code returns, Generac says dealer service is required. On a portable, most starting problems come down to stale fuel, low oil, the choke or the fuel valve.
How we put this guide together
We have not serviced these generators. The light meanings, error codes and reset steps come from Generac’s official support site, including its error code list, its status light guide, its articles on overcrank, low oil pressure, low battery and overload alarms, and its portable generator quick reference guide. Product box details come from current Amazon listings. Your owner’s manual is the final word for your model.
Before you touch anything
A standby generator can start by itself at any moment when it is in AUTO. Generac warns never to start a generator while it is under load, and it does not recommend that owners modify or service the internal wiring. If you smell gas, see damage or feel unsure, stop and call a Generac dealer or Generac Customer Service on 1-888-436-3722.
In this guide
- Step One: Know Which Generac You Have
- What the Status Lights Mean on a Generac Standby Generator
- Alarms, Warnings and Maintenance Reminders
- Common Generac Standby Error Codes
- How to Clear a Generac Alarm Safely
- Fixes You Can Try on a Generac Standby Generator
- Running a Standby Generator Through a Long Outage
- Generac Portable Generator Troubleshooting
- When to Call a Generac Dealer
- Parts That Prevent Problems
- Common Generac Troubleshooting Mistakes (and the Fix)
- Pro Tips for Fewer Surprises
- Real-Life Scenarios: What Would You Do?
- Generac Generator Troubleshooting: FAQ
- Your Generac Troubleshooting Checklist
Step One: Know Which Generac You Have
The right steps depend on the type of generator and the controller it uses. Generac’s support articles sort them like this.
| Generator | Controller | Where you see the code |
|---|---|---|
| Next Generation air-cooled home standby, 10 to 28 kW | Power Zone 200 | In the Mobile Link app only. This controller has no display. |
| Guardian Series air-cooled home standby, 2017 to present | Evolution, Sync or Nexus | On the controller’s LCD screen, or in Mobile Link |
| Liquid-cooled home standby | Evolution or Power Zone 410 | On the controller display |
| Portable generators | No error code screen on most models | Lights on the panel, or a flashing fault lamp on large EFI models |
Not sure which you have? Lift the lid at the front of a standby unit. Generac says the controller sits at the top right. On an air-cooled unit, a screen means a Guardian with an Evolution or Nexus controller. Buttons and lights with no screen mean a Next Generation model.
What the Status Lights Mean on a Generac Standby Generator
Generac home standby generators show their status with LED lights behind a clear lens on the side of the unit. You can read them from across the yard.
| Light | What it means | What to do |
|---|---|---|
| Green, steady | Utility power is present and the generator is in AUTO. It is ready. | Nothing. This is normal. |
| Green, flashing | The generator is running and powering the home in an outage. | Nothing. This is normal. |
| Yellow | A warning is active or maintenance is due. Generac says the generator should still run in an outage. | Check the message and deal with it soon. |
| Red | The generator is OFF, or an alarm has shut it down. | Find the code. Dealer service may be needed. |
| Blue, Next Generation models only | The control panel is in SERVICE mode. | Take it out of service mode when work is finished. |
Two more details help.
- Lights can combine. A yellow maintenance light can show together with green or red. Generac notes that red and yellow together can look orange.
- The light is only the headline. For the full story, check the control panel, the Mobile Link app or the Mobile Link website.
Key insight: yellow means “look at me soon.” Red means “I have stopped.” Treat them very differently.
Alarms, Warnings and Maintenance Reminders
Generac sorts its messages into three groups.
- Alarms turn the light red. The generator has shut down or will not start.
- Warnings turn the light yellow. Something needs attention, but the generator can still run.
- Maintenance reminders also turn the light yellow. They tell you a service is due.
Generac adds one rule that surprises people: a warning must be fixed before the message will clear. You cannot simply dismiss it. Some alarms and maintenance reminders can be cleared from the panel once you have dealt with them.
One thing is not an error at all. A number followed by an H in brackets, such as 45091 (H), is the “hours of protection” counter. Generac says owners often mistake it for a fault code.
Common Generac Standby Error Codes
Generac calls these error codes, alarm codes or fault codes. They all mean the same thing. This table covers the ones owners meet most often.
| Code | Name | Light | What it is telling you |
|---|---|---|---|
| 1100 to 1101 | Overcrank | Red | The engine turned over but did not start. It tries 5 times before the alarm. |
| 1200 to 1207 | Overspeed | Red | The engine ran too fast. |
| 1300 | Low Oil Pressure | Red | The oil pressure sensor shut the unit down, usually because the oil level is low. |
| 1400 to 1401 | High Temperature | Red | The engine got too hot. |
| 1500 to 1521 | RPM Sensor | Red | The controller lost the engine speed signal. |
| 1600 to 1603 | Underspeed | Red | The engine ran too slowly. |
| 1900 to 1916 | Undervoltage | Red | The output voltage was too low. |
| 2100 to 2103 | Overload Remove Load | Red | The home asked for more power than the generator can give. |
| 2098 to 2099 | Wiring Error | Red | The sensing wires to the transfer switch are miswired. |
| 2750 | Low Battery | Red | The battery charge has fallen too low. |
| 2770 | Charger Warning | Yellow | The battery is not charging properly. |
| 2780 | Charger Missing AC | Yellow | The battery charger is not getting AC power. |
| 2800 | Auxiliary Shutdown | Red | The emergency shutdown switch is off. Owners can usually fix this. |
| 3217 | Low Fuel Pressure | Yellow | Fuel pressure at the engine is low. |
Cannot find your exact number? Generac suggests looking at the first two digits. Its article for code 1500 generally applies to 1501, 1505 and the rest of that family.
Most codes are also listed in your owner’s manual.
How to Clear a Generac Alarm Safely
Clearing an alarm does not fix anything. It only lets the generator try again. So correct the cause first, then clear it once.
Generac’s steps depend on the controller.
Next Generation models (Power Zone 200)
- Hold the OFF button for at least three seconds. Generac says the red light turns solid when the alarm is cleared.
- Press AUTO to return the generator to service.
- Watch it. If the alarm returns, contact a Generac authorized service dealer.
Guardian models with an Evolution or Sync controller
- Check the shutdown switch on the back of the generator. It must be in the I position, which is pressed in at the top.
- Lift the lid and find the controller at the top right.
- Press the red OFF button, then ENTER, as the screen tells you.
- Press the green AUTO button. The generator is ready to start in the next outage.
Guardian models with a Nexus controller
- Move the rocker switch to OFF.
- Press ENTER twice.
- Move the rocker switch back to AUTO.
One reset, not ten
Generac’s advice for liquid-cooled models applies to every generator: never clear an alarm without correcting the cause. Clearing the same alarm again and again can damage the generator or make it unsafe. If the code comes straight back, stop and call a dealer.
The dealer test
Generac gives owners a simple way to tell whether a code needs a dealer.
- Clear the alarm using the steps for your model.
- Press MANUAL to try a manual start.
- If the code returns, dealer service is required.
- If it starts, it will keep running until you press AUTO or OFF.
Fixes You Can Try on a Generac Standby Generator
For these common alarms, Generac lists checks an owner can safely make before calling for service.
Overcrank (code 1100): it cranks but will not start
Generac says the engine tries to crank 5 times. If it does not start, the overcrank alarm appears. The usual causes are fuel supply problems or missed maintenance.
- Check that the fuel shutoff valve is ON. If it is closed, no fuel reaches the engine.
- On propane, check the tank level. Generac says pressure can drop when the tank falls below 30%, and that can cause this alarm.
- On natural gas, ask your gas supplier about problems in your area. Big outages and construction can affect supply.
- Look at the air filter. A blocked filter is on Generac’s list of causes.
- Check the battery. A low battery is also on the list.
- Clear the alarm and try a start in MANUAL. Sometimes it is a one-time event.
Leave fuel pressure to a professional. Generac says that test needs special equipment and must be done by a technician.
Low Oil Pressure (code 1300)
The oil pressure sensor has shut the engine down. Generac says the usual cause is a low oil level from normal use, a leak or missed maintenance.
- Let the generator cool for at least 30 minutes. That avoids burns and false readings.
- Check the oil level and top it up. Make sure the dipstick is pushed all the way in.
- Check the caps and filter. The fill cap, drain cap and oil filter should all be hand-tight.
- Look for leaks. Clean up any oil you find and dispose of it properly.
- Clear the alarm and return the unit to AUTO.
Low Battery (code 2750)
The battery starts the engine and powers the controller, so a weak one causes many odd faults.
- Generac says the battery should measure at least 12.5 volts DC.
- If it reads lower, give it 24 hours to charge.
- If it still reads low after that, the battery may need replacing.
- If it reads above 12.5 volts, the charger is the next thing to check.
- On a new installation, Generac says a charger warning can mean a neutral wire for the charger circuit was left out. That is a job for the installer.
Overload Remove Load (codes 2100 to 2103)
The house asked for more power than the generator is rated to supply.
- Decide what is not essential. An electric dryer or oven is a typical example.
- Turn those loads off by unplugging them or switching off their breakers in the main panel.
- Turn the generator’s main line circuit breaker OFF, so it does not start under load.
- Turn the utility main breaker OFF.
- Clear the alarm and set the generator to AUTO.
- Let the engine warm up for one to two minutes, then turn the generator’s main line circuit breaker ON.
- Turn the utility main breaker back ON, so the system can tell when utility power returns.
- Keep to essentials for the rest of the outage. Generac gives the sump pump and refrigerator as examples.
If you have a Generac Load Manager, check that it is working and that its lockouts are set correctly. If the alarm keeps returning, remove more loads or call a dealer.
Auxiliary Shutdown (code 2800)
This is the code owners can most often fix themselves. It means the emergency shutdown switch is off.
On Guardian models, find the switch on the back of the generator and make sure it is in the I position. Generac notes that 13 kW and larger units have a second switch on the inside panel. Then clear the alarm and press AUTO.
A blank control panel
Generac says the display is powered by the generator’s battery. A blank screen usually points to one of four things.
- A battery that is discharged or disconnected.
- A blown 7.5-amp fuse.
- A damaged or disconnected T1 circuit.
- A controller that needs a reset.
Start by pressing ENTER or ESCAPE a few times. Then check that the battery is connected and charged. Generac asks owners to leave the internal wiring to a certified dealer.
Running a Standby Generator Through a Long Outage
A standby generator can run for days, but it still needs looking after. Generac’s guidance is clear.
Tip: the 24-hour rule
In a long outage, Generac says the unit should be shut down every 24 hours for 30 minutes. That lets it cool so you can check the oil level and add oil if needed. Skipping it raises the risk of a low oil pressure shutdown when you can least afford one.
Our emergency power outage checklist covers the rest of an outage plan.
Generac Portable Generator Troubleshooting
Portable generators are simpler. Most have no error code screen, so you work from the symptom. Generac’s quick reference guide for portables lists these causes and fixes.
| Symptom | Likely causes | Fix |
|---|---|---|
| Will not start, or runs rough | Fuel shut-off is OFF, out of fuel, stale fuel or water in fuel | Turn the fuel on. Drain old fuel and refill with fresh gasoline. |
| Will not start, or runs rough | Too much choke, dirty air filter, bad spark plug, plug wire off | Set the choke to the no-choke position. Clean or replace the filter and plug. Reconnect the wire. |
| Will not start, or shuts off right away | Low oil level | Fill the crankcase to the correct level. |
| Shuts down while running | Out of fuel, low oil, or a COsense shutdown | Refuel, check the oil, or move the generator. See the light guide below. |
| Engine runs but no power at the outlets | Circuit breaker open, GFCI tripped, bad cord or bad appliance | Reset the breaker or GFCI. Try another cord and another device. |
| Bogs down when you plug something in | Overloaded, stale fuel, clogged carburetor or spark arrestor | Reduce the load. Use fresh fuel. Clean the carburetor and the spark arrestor screen. |
| Surges or stumbles | Choke opened too soon, bad spark plug, clogged carburetor | Set the choke halfway until it runs smoothly. Replace the plug. Clean the carburetor. |
| Pull cord will not rewind | Damaged recoil spring | Dealer |
Generac’s support site names the most common cause of all: old fuel left in the system, which clogs the carburetor. Its portable FAQ says fuel begins to break down within about a month.
What the COsense lights mean
Many Generac portables have COsense, which shuts the engine off if carbon monoxide builds up. A light on the side panel badge tells you why it stopped.
- Blinking red: carbon monoxide was building up. Move the generator to an open area outdoors, far from windows, doors and vents.
- Blinking yellow: a fault in the COsense system. If it keeps happening, Generac says to contact a dealer.
Wind matters too. Generac notes that if the exhaust is blown back toward the sensor, it can trigger a shutdown even outdoors.
Read the spark plug
Generac’s troubleshooting guide uses the spark plug as a clue when an engine cranks but will not fire.
- A wet plug points to flooding. Look at the choke setting and the carburetor.
- A dry plug means fuel is not reaching the engine. Check the fuel supply and the shutoff valve.
Flash codes on the big EFI portables
Generac’s GP15500EFI and GP18000EFI have a fault lamp that flashes a two-digit code. Long flashes are the first digit and short flashes are the second.
| Flash code | Meaning | What to do |
|---|---|---|
| 1-1 | Carbon monoxide above the limit | Move the generator. Never run it indoors or in a partly enclosed area. |
| 1-3 | Battery voltage low | Charge the battery. |
| 5-2 | Engine speed fault | Fill the fuel tank. If it continues, see a dealer. |
| 6-1 | Low oil pressure | Fill the crankcase to the correct level. |
| Any other code | Several possible causes | Contact a Generac service dealer. |
To clear an active shutdown code on those models, Generac says to turn the key to OFF first.
For more on these symptoms, see why a generator won’t start and why a generator keeps shutting off.
When to Call a Generac Dealer
Generac is direct about this. Its support site says most error codes “exceed typical DIY troubleshooting” and may need an Independent Authorized Service Dealer, which it shortens to IASD.
Call a dealer when:
- The same code returns after one reset and a manual start.
- The code points to the controller, wiring or engine electronics. Examples from Generac’s list include Controller Fault, Wiring Error, Overspeed, Underspeed, Overvoltage and Undervoltage.
- Fuel pressure needs testing.
- You have a liquid-cooled generator. Generac says not every dealer is trained for these, so confirm before you book.
- You smell gas or see damaged parts.
How to get service
- Find your serial number. Generac’s service request form asks for it.
- Use the dealer locator on Generac’s website and choose “Maintenance and Service”.
- Or send a service request. Generac says it will notify a top-rated local provider for you.
- For urgent problems, Generac advises calling a dealer near you directly.
- Have the code ready. Note the number, the light color and what the generator was doing when it stopped.
Generac’s customer service line is 1-888-436-3722. Our guide to whole-house generators explains how these systems fit together, which helps when you talk to a technician.
Parts That Prevent Problems
Many alarms trace back to skipped maintenance. Generac sells kits that hold the filters and spark plugs for a routine service. These two had active Amazon listings when we checked in October 2026.
For 20 to 26 kW units
Generac 6485 Scheduled Maintenance Kit for 999cc Standby Generators
The service kit for Generac’s larger air-cooled home standby generators. It holds the parts that wear, in one box, with instructions.
- Fits20, 22, 24 and 26 kW air-cooled
- Engine999 cc V-twin, 2013 or later
- Air filterIncluded, with pre-cleaner
- Oil filterIncluded
- Spark plugsTwo, pre-gapped
- Service intervalEvery 200 hours or 2 years
- Why it works: every part is a genuine Generac component chosen for this engine, so there is no guessing over part numbers.
- Who it is best for: owners who are comfortable changing oil and filters, and want to do the routine service themselves.
- What it solves: yellow maintenance lights, and faults linked to dirty air filters and worn plugs.
- Handy extras: an angled funnel, a cloth, a reminder sticker and a step-by-step manual. The listing says no special tools are needed.
- Keep in mind: engine oil is not included. The listing says to buy 5W-30 full synthetic separately. Check your engine size and build year before you order.
As an Amazon Associate we earn from qualifying purchases. Specs come from the Amazon listing, checked October 2026.
For 12 to 18 kW units
Generac 6484 Maintenance Kit for 12-18 kW Generators
The matching kit for Generac’s mid-size air-cooled standby generators. It follows the same idea: one box, all the service parts.
- Fits12 to 18 kW air-cooled
- Engine760 to 990 cc, 2013 or later
- Air filterIncluded, with pre-cleaner
- Oil filterIncluded
- Spark plugsTwo, pre-gapped
- Service intervalEvery 200 hours or 2 years
- Why it works: the plugs arrive gapped for the engine, and the kit includes its own instruction manual.
- Who it is best for: owners of 12 to 18 kW Generac units, including the Honeywell and Centurion models Generac built with the same engines.
- What it solves: it keeps the service on schedule, which helps you stay inside Generac’s warranty conditions.
- Handy extras: an oil funnel, a chamois and a reminder sticker.
- Keep in mind: oil is sold separately. Service more often in dusty conditions, and confirm the fit against your model number.
As an Amazon Associate we earn from qualifying purchases. Specs come from the Amazon listing, checked October 2026.
Own a smaller unit? Generac lists a 6482 maintenance kit for 8 to 10 kW generators too. For a portable, keep fuel fresh with a stabilizer such as STA-BIL Storage, and follow our generator maintenance checklist.
Common Generac Troubleshooting Mistakes (and the Fix)
Pro Tips for Fewer Surprises
- Set up Mobile Link. Generac says it sends status alerts by text, email and push notification, so you hear about a fault before the next storm.
- Write the model and serial number inside the manual, and keep a photo of the data plate on your phone.
- Keep the area clear. Leaves, snow and plants around the enclosure can block the air the engine needs.
- Replace the battery before it fails. A weak battery shows up as several different faults.
- Keep a log. Note each code, the date and what fixed it. Patterns help a technician.
- Service on hours or time, whichever comes first. The Generac kit listings state every 200 hours or 2 years. Check your manual for your own model’s schedule.
Real-Life Scenarios: What Would You Do?
These are typical situations that owners describe in forums and reviews. They are examples to help you think it through, not quotes from real people.
🟡 The yellow light in spring
You notice a yellow light on the side of the standby unit. Everything else seems normal.
Open Mobile Link or lift the lid and read the message. It is often a maintenance reminder or a battery warning.
Next step: service it or check the battery
🔴 The red light in a storm
The power is out and the generator tried to start, then stopped with code 1100. The propane gauge reads 20%.
The tank is below the 30% level Generac warns about. Low fuel pressure is a likely cause.
Next step: get propane delivered, then clear and retry
⛽ The portable that will not start
The generator sat in the garage since last year with fuel in the tank. It cranks but will not fire.
Stale fuel is the most common cause Generac names.
Next step: drain it, add fresh fuel, check the oil and the plug
Generac Generator Troubleshooting: FAQ
What does a red light mean on a Generac generator?
On a home standby generator, Generac says a red light means the unit is OFF or an alarm has shut it down. Find the error code on the control panel or in the Mobile Link app. If the code returns after you clear it once and try a manual start, dealer service is required.
What does a yellow light mean on a Generac generator?
A yellow light means a warning is active or maintenance is due. Generac says the generator should still run during an outage, but the alert should be dealt with promptly. A warning will not clear until the cause is fixed.
How do I reset a Generac generator?
It depends on the controller. On Next Generation models, hold the OFF button for at least three seconds, then press AUTO. On Guardian models with an Evolution controller, press OFF, then ENTER, then AUTO. Always correct the cause before you clear an alarm.
What does Generac code 1100 mean?
Code 1100 is Overcrank. The engine turned over but did not start after 5 attempts. Generac lists fuel supply problems, a closed fuel valve, a dirty air filter and a low battery among the causes. Check that the fuel valve is on, and that a propane tank is above 30%.
Why does my Generac portable generator keep shutting off?
Generac's quick reference guide lists running out of fuel, a low oil level and a COsense shutdown. A blinking red light on the side badge means carbon monoxide was building up, so move the generator to an open area away from the house.
Can I service a Generac standby generator myself?
Routine maintenance such as oil, filters and spark plugs can be done by a confident owner, and Generac sells kits for it. Generac does not recommend that owners modify or service the internal wiring, and fuel pressure tests must be done by a professional.
Your Generac Troubleshooting Checklist
- Note the light color: green, yellow, red or blue.
- Find the code on the control panel or in Mobile Link.
- Check the simple things first: fuel valve, fuel level, oil level and battery.
- Fix the cause before you clear anything.
- Clear the alarm once, using the steps for your controller.
- Try a manual start with no load connected.
- If the code returns, stop and call a Generac dealer.
- Have your model, serial number and the code ready.
- In a long outage, shut down every 24 hours for 30 minutes and check the oil.
- Book routine maintenance so the next fault never happens.
The bottom line
Most Generac faults give you a color and a code. Yellow is a job for the weekend. Red gets one careful reset, then a dealer. Keeping up with maintenance prevents most of them.
As an Amazon Associate we earn from qualifying purchases.
Sources: Generac’s official support site (support.generac.com): the home standby error code list, the status indicator light guide, the alarm reset guide, the dealer-required code list, the articles on Overcrank 1100, Low Oil Pressure 1300, Low Battery 2750, Overload 2100 and a blank control panel, the portable generator quick reference guide and the EFI portable fault code article; Generac’s portable generator FAQ; Amazon listings for the products named in this guide. All checked October 2026.
