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Generac 1902 and other undervoltage codes (1900–1906)

By How House Works EditorialBased on Generac manuals and Help CenterChecked against sources Updated

Generac controller or Mobile Link

1900–1906

“Undervoltage”

Guardian, Next Generation · What Error Codes Do I Need to Call a Dealer For?; What Does It Mean When My Generator Displays an alarm: Undervoltage, error codes 1900-1916?; Guardian 10–26 kW Owner's Manual, p. 34; Next Generation 10–28 kW Owner's Manual, p. 38
Technician

Includes 1902. Next Generation table: 1900–1907; the title of Generac's article says 1900–1916. Owner's manuals: UNDERVOLTAGE, “Contact an IASD.” (Guardian 10–26 kW Owner's Manual, p. 34; Next Generation 10–28 kW Owner's Manual, p. 38).

What it means

The generator is not producing proper voltage, either over a stretch of time or through a sudden loss (Generac Help Center, “What Does It Mean When My Generator Displays an alarm: Undervoltage, error codes 1900-1916?”, Aug 26, 2025). Generac links it to fuel supply or fuel selection, circuitry, firmware or voltage production, and says the electrical side of the problem usually needs an IASD, Generac’s Independent Authorized Service Dealer, to diagnose. The same article names 1902 directly: in extreme weather, heavy demand on the gas grid can reduce the fuel reaching the unit, which may cause it. The owner’s manuals’ remedy for UNDERVOLTAGE is to contact an IASD Guardian 10–26 kW manual, p. 34; Next Generation manual, p. 38.

The Guardian manual describes one more case. If frost or dust and dirt keep the generator from building normal voltage, the controller runs a cleaning cycle, an extended warm-up of several minutes shown as “Warming Up”. If the cleaning cycle fails, the display shows “Under Voltage” Guardian 10–26 kW manual, p. 21.

Check these first

  1. After a failed cleaning cycle on a Guardian unit, the manual says the alarm can be cleared after several minutes and the generator restarted. If the problem persists, make no further attempts to start it and contact an IASD Guardian 10–26 kW manual, p. 21.
  2. On propane, check that the tank is above 30% (1900 article).
  3. On natural gas during a widespread outage, ask the gas company whether the gas supply is stable (1900 article). If you smell gas, follow Generac’s gas leak steps.
  4. On a Guardian unit, check that the fuel selected in the controller, NG or LP, matches your fuel (1900 article). The setting has to match the fuel jet position, which is set during installation; the article notes the jets are rarely the problem on units that have been in service for a while.
  5. In winter, clear snow from around the unit (1900 article).
  6. Clear the alarm for your series and start the unit in MANUAL with no load (1900 article).

When to call a licensed technician

  • The alarm comes back. That is the manuals’ remedy Guardian 10–26 kW manual, p. 34.
  • The electrical diagnosis. The 1900 article says the electrical nature of this alarm usually requires advanced diagnosis by an IASD.
  • A new installation. The 1900 article says to have the unit checked against the installation manual and to contact an IASD.
  • Fuel supply. The article says this alarm can also come from too little fuel supply. The fuel source must be connected by a qualified professional technician or contractor Guardian 10–26 kW manual, p. 3.
  • The air filter, which the article mentions for freezing weather. Generac recommends that an IASD do all maintenance Guardian 10–26 kW manual, p. 22.

Notes for different models

Generac’s Guardian table lists Undervoltage as 1900–1906 and its Next Generation table as 1900–1907 (Generac Help Center, “What Error Codes Do I Need to Call a Dealer For?”, Sep 21, 2026). The 1900 article’s title says 1900–1916 and its overview 1900–1906. The fuel check in step 4 is for Guardian units only; on Next Generation units, the 1900 article says fuel conversion is done in the Field Pro app during installation.

Related Generac codes

  • 1600 “Underspeed”
  • 1800 “Overvoltage”
  • 2299 “Undervoltage Overload”

See also

All Generac codes

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Sources

  1. Generac Power Systems, Inc.. Guardian 10–26 kW Owner's Manual. Part No. A0001846499 Rev. C, 05/12/2023; cover title: Owner's Manual, 60 Hz Air-Cooled Generators, 10 kW to 26 kW; Evolution 2.0 / Sync 3.0 menu; printed page numbers (PDF page minus 3). Accessed Oct 13, 2026.
  2. Generac Power Systems, Inc.. Next Generation 10–28 kW Owner's Manual. Part No. A0004332577 Rev. C, 04/24/2026; cover title: Owner's Manual, 60 Hz Air-Cooled Generators, 10 kW to 28 kW; Power Zone 200 controller; printed and PDF page numbers match. Accessed Oct 13, 2026.
  3. Generac Help Center (Generac Power Systems, Inc.). What Error Codes Do I Need to Call a Dealer For?. Web article dated Sep 21, 2026 on the page; holds Generac's Next Generation and Guardian code tables. Accessed Oct 13, 2026.
  4. Generac Help Center (Generac Power Systems, Inc.). What Does It Mean When My Generator Displays an alarm: Undervoltage, error codes 1900-1916?. Web article dated Aug 26, 2025 on the page. Accessed Oct 13, 2026.