Generac Error Code 1100: Overcrank
Code 1100 means the engine cranked but never started. The controller tries five cranking cycles; if the engine doesn't catch, it locks out with a red light, OVERCRANK on the screen, and code 1100. Generac's own checklist is short: fuel valve open, correct fuel selected, enough propane in the tank, air filter clear, battery good. Clear the alarm (OFF → ENTER → AUTO), start it in MANUAL, and if it still won't run — or runs rough — that's a dealer call.
What code 1100 means
On an Evolution or Evolution 2.0 controller the display alternates between the number 1100 and the word OVERCRANK every five seconds, and the red ALARM LED is on. Generac's error-code list groups 1100 and 1101 together as "Overcrank," with the Mobile Link message "The generator has experienced an overcrank alarm. Please contact a dealer."
The definition in the Evolution diagnostic manual is plain: "Engine cranks but will not start (5 crank attempts)." The owner's manual spells out the five cycles:
- 10 kW units: 15 seconds cranking, 7 seconds rest, then four more cycles of 7 seconds cranking / 7 seconds rest.
- 14–26 kW units: 16 seconds cranking, 7 rest, 16 cranking, 7 rest, then three more cycles of 7 on / 7 off.
If the engine hasn't fired by the end of the fifth cycle, the controller stops cranking and posts the alarm. It will not try again on its own — which is the whole reason you're looking at a dark house.
| Code | Display | Meaning (Generac wording) | Severity | DIY? |
|---|---|---|---|---|
| 1100 | OVERCRANK | Engine cranks but will not start after 5 crank attempts | Unit will not run | Check, then call |
| 1101 | OVERCRANK | 8–9 kW Evolution 1.0 only: crank cycles limited to 10 to protect the starter motor | Unit will not run | Check, then call |
| — | OVERCRANK (Nexus) | Older Nexus controllers show the word with no number; same protective function | Unit will not run | Check, then call |
A note on 1102: it circulates on forums, but it does not appear in Generac's published code list or in the Evolution diagnostic manual. Treat anything you read about "1102" as unverified.
Reset procedure (as the manual states it)
Generac's rule, verbatim from its support page: "Never clear an alarm without correcting the cause." Do the checks in the next section first, then:
Evolution / Evolution 2.0 / Sync (Guardian, 2013 and newer)
- Confirm the external shutdown switch on the back panel is in the I (closed) position; on 13 kW and larger units check the internal switch as well.
- Press the red OFF button.
- Press ENTER when the display prompts you (some units want it pressed twice).
- Press the green AUTO button.
- To test, press the blue MANUAL button. The generator should crank and run. Put it back in AUTO when you're done.
PowerPact 7.5 kW
Same sequence, but press OFF twice to reach the alarm; three times if a maintenance reminder is showing alongside it.
Nexus (pre-2013, rocker switch)
Move the rocker to OFF, press ENTER twice, move it back to AUTO. Units without a rocker: OFF button, then ENTER twice.
Step-by-step diagnosis
Everything below is what Generac lists in its 1100 support article and the owner's manual troubleshooting table, in the order most likely to be the problem. Nothing here requires opening the engine.
- Is the fuel shutoff valve on? There's a valve on the gas or propane line at the generator (and usually another at the meter or tank). A valve handle in line with the pipe is open; across the pipe is closed. Contractors, a recent gas-company visit, or a curious kid close these more often than you'd think.
- If it was closed → open it, clear the alarm, start in MANUAL. Expect one or two extra cranks while the line refills.
- If it was open → step 2.
- Propane tank above 30 %? Generac wants LP above 30 %. Below that, tank pressure on a cold day can't feed the regulator at full engine demand. Natural gas customers: skip to step 3, but ask yourself whether the utility had an outage or pressure drop.
- If the tank is low → fill it, then retest. Ask the supplier to check regulator delivery pressure while they're there.
- Is the fuel selection right? Air-cooled Guardians are convertible between natural gas and propane; the fuel jet and (on some units) a controller setting must match. A unit installed on NG but flipped to LP during a service visit will crank forever. The installing dealer records the fuel setting; check with them rather than changing anything yourself.
- If wrong → contact the installing dealer; changing fuel involves the gas train.
- Air filter blocked or iced? Open the air box and look. A filter packed with cottonwood fluff, mud-dauber nests, or ice after a storm will starve the engine on the crank. Replace, don't wash (paper element).
- Part numbers: 0J8478S (14–26 kW), 0E9371AS (10 kW) on current Evolution 2.0 units; older units use 0J8478 / 0E9371A — confirm against your owner's manual.
- Battery. A battery that will spin the starter for one 16-second cycle but sags by the third is a classic overcrank. From the MAIN MENU, go to BATTERY: GOOD means move on; CHECK BATTERY means replace it. Generac specifies a Group 26R wet cell, 540 CCA minimum (or Group 35 AGM, 650 CCA). Also check that the charger's AC feed hasn't been tripped — a 2770 or 2780 warning in the alarm log points that way.
- If the battery is weak → replace it (Generac part 0H3421S is the Group 26R). Clear the alarm and retest.
- Clearance and snow. Generac asks for three feet of clearance all around and no snow over the intake louvers. Buried units crank rich and won't light.
- Still overcranking? Clear the alarm once more and try MANUAL while you stand next to the unit. Listen: cranking with no cough at all points to fuel or spark; a cough that never catches points to fuel pressure, the stepper motor/choke on the mixer, or valve lash on a unit that's overdue its 400-hour service. Those are dealer diagnostics — the diagnostic manual sends a technician into "Problem 17 – Engine Cranks but Will Not Start," a multi-page flowchart with a manometer and a test light.
Parts, numbers, and consumables
Only parts Generac lists in its own owner's manuals for the 10–26 kW air-cooled line are shown. Older 8–20 kW Nexus units use different filters — check your manual's "Specifications" table.
| Part | Part number | Fits | Where verified |
|---|---|---|---|
| Battery, Group 26R, 540 CCA | 0H3421S | 10–26 kW air-cooled Guardian | Owner's manual A0001846499 / A0000973303 |
| Air filter | 0J8478S (older: 0J8478) | 14–26 kW | Owner's manuals |
| Air filter | 0E9371AS (older: 0E9371A) | 10 kW | Owner's manuals |
| Spark plug (RC12YC equivalent) | 0G0767A | 14–26 kW (two plugs) | Owner's manuals |
| Spark plug | 0G0767B | 10 kW (one plug) | Owner's manuals |
| Oil filter | 070185ES (older: 070185E) | 10–26 kW | Owner's manuals |
| Control panel fuse | 0D7178T | 10–24 kW | Owner's manual A0000973303 |
Generac sells these bundled as maintenance kits keyed to your generator's model number (G00xxxxx), not its kW rating. The kit article on Generac's support site lists the current kit numbers.
Repair or replace?
An overcrank is almost never the end of a standby generator. The typical resolution is a closed valve, a low propane tank, a $30 filter, or a $150 battery. The expensive versions — a failed fuel regulator, a bad stepper motor on the mixer, or a valve adjustment — are still a few hundred dollars in dealer labor on a $5,000–$9,000 machine. Replace the generator only if it's a Nexus-era unit (pre-2013) with multiple failing systems and an out-of-production controller; parts for those are drying up.
When to call a dealer
- The unit cranks fine, fuel is confirmed on and at pressure, the filter is new, the battery reads GOOD, and it still won't catch.
- It starts in MANUAL but overcranks again the next time it tries on its own (points to fuel pressure under load or a marginal battery/charger).
- You smell gas at the unit, or the fuel selection looks wrong — the gas train is licensed work.
- The alarm log shows 1100 alongside 1505 (RPM sense loss) or 2770/2780 (charger) — a technician needs the whole history.
- Generac's support line is 1-888-436-3722; the dealer locator is on generac.com. Warranty work must go through an Independent Authorized Service Dealer (IASD).
Parts and supplies mentioned on this page
If a part number above matches your manual, these searches will find it. Verify the fit against your model number before ordering.
- Generac 0H3421S Group 26R battery (10–26 kW air-cooled)Check price on Amazon
- Generac air filter 0J8478S (14–26 kW) or 0E9371AS (10 kW)Check price on Amazon
- Generac spark plug 0G0767A (14–26 kW)Check price on Amazon
Related codes and symptoms
An overcrank that turns into a 1505 RPM Sense Loss on the next attempt usually means the same weak battery. A 1902 Undervoltage after a rough start means the engine ran but the alternator didn't come up — different problem, different page. And if the unit starts and then dies within a few seconds, look at 1300 Low Oil Pressure before anything else.
Not sure the generator can carry the load?Generator Wattage Calculator Running watts, the largest starting surge, and a generator class from manufacturer charts.Frequently asked questions
Can I just clear the 1100 alarm and try again?
You can, and Generac says that for many overcranks "clearing the alarm and attempting to restart the unit is all that is needed." But its support article also says never to clear an alarm without correcting the cause. If you clear it and it starts, fine — then go find out why it overcranked so it doesn't happen during the next outage.
Why did my generator overcrank during its weekly exercise but start fine in MANUAL?
The exercise cycle happens at a set time regardless of weather; a cold propane tank, a marginal battery, or ice in the air intake can fail then and be fine an hour later. Check the battery reading and the propane level first.
Does code 1100 mean the starter is bad?
Not by itself. 1100 says the engine turned over and didn't fire. If the starter were dead the unit would not crank at all and you'd more likely see an RPM sense code (1505 on twin-cylinder units, 1515 on single-cylinder). A starter that spins slowly on a good battery is a dealer diagnosis.
What is the difference between 1100 and 1101?
Both display OVERCRANK. Per the Evolution diagnostic manual, 1101 is specific to the 8–9 kW Evolution 1.0 units, where the controller caps cranking at ten attempts to protect the starter. The checks are the same.
Will Mobile Link tell me it's an overcrank?
Yes. Generac's code list gives the Mobile Link message as "The generator has experienced an overcrank alarm. Please contact a dealer," and the app's status history shows the code number if the unit is enrolled.