Overvoltage: Output More Than 10% Above Nominal
The GENERAC-1800 (Generac Evolution) diesel fault code means: Overvoltage: Output More Than 10% Above Nominal. This is a serious severity code.
- Keep running?
- No — shut it down
- DIY difficulty
- moderate
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What Are the Symptoms of GENERAC-1800?
- The generator shuts down with an Overvoltage alarm
- Code 1800 in the controller history or Mobile Link
What Causes GENERAC-1800? (Most Likely First)
- Generator output voltage stayed more than 10% above nominal for three seconds Very Likely
Can I Keep Running It with GENERAC-1800?
No — shut it down. GENERAC-1800 is rated serious severity. Continuing to run the unit in this state risks further damage — get it looked at before putting it back in service.
Frequently Asked Questions
What does Generac code 1800 mean?
Overvoltage: Generac's Power Zone 410 manual defines it as the output staying more than 10% above nominal voltage for three seconds. It is not an overcrank code; Generac's overcrank codes are 1100-1101.
Is 1801 the same?
Both are overvoltage. Generac defines 1801 as an instantaneous reading 30% over nominal, and 1800 as a prolonged one.
Mechanics Guide Step-by-step diagnosis
How Do You Diagnose GENERAC-1800?
Note what was running when it shut down; Generac defines 1800 by the voltage measurement, not by a single cause.
Clear the alarm and restart: on Evolution controllers press OFF, ENTER twice, then AUTO; on Power Zone controllers follow the owner's manual. If the code comes back, Generac recommends a Generac Independent Authorized Service Dealer (IASD).
Sources 1
This page is built from documented references. Verify against your own service info before repair work.
Which Vehicles Commonly Get GENERAC-1800?
- Generac standby generators with a Power Zone 410 controller (the code table this page is checked against)
- Generac lists the same code family on its air-cooled home standby support pages
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