1600 — Generac 1600 — Underspeed
Alarm 1600 is Underspeed: the engine slowed below the required speed (about 55 Hz on a 60 Hz unit for ~30 seconds) and shut down. It is NOT an overspeed code. (Meaning corrected against official Generac support documentation / Evolution controller e-code list; older Nexus controllers may differ — confirm for your unit.)
- Keep using it?
- Limited use only
- DIY difficulty
- Moderate
- Verified against
- support.generac.com ↗
How to fix it
- Reduce or shed load and retry.
- Verify adequate fuel pressure/supply and gas-line sizing.
- Check and clean/replace the air filter.
- If it persists at normal load, have a dealer check the governor and engine.
Why it happens
Typical signs: Shutdown, often under load · 1600 / Underspeed in the alarm log · Engine bogs down or runs rough before stopping
- Overload Connected load exceeds what the generator can carry.
- Restricted fuel delivery Low gas pressure or undersized gas line starves the engine under load.
- Dirty air filter Restricted air reduces power.
- Governor / stepper-motor or engine mechanical issue Cannot hold rated speed.
Parts you may need
If diagnosis points to a failed part, these are the common replacements. As an Amazon Associate we earn from qualifying purchases.
- Generac generator air filter Common replacementAmazon →
More Generac generator codes
Always unplug an appliance before servicing it. This guide is for informational purposes and is not a substitute for a qualified technician. Verified against manufacturer documentation: support.generac.com.