Generac — Checking No-Load Voltage and Frequency
Testing & diagnosis · Generator AC output
From a Generac service manual covering: NP-50G, NP-50LP, NP-66G/LP, Q-40G, Q-55G/LP, Q-70G/LP. Check it applies to your exact model before use.
Applies to: Generac NP-50G, Generac NP-50LP, Generac Q-40G, Generac NP-50G/LP engine
Procedure
- Connect an accurate AC voltmeter and AC frequency meter across generator AC output leads.
- With generator running, stabilized, and warm, check AC frequency and voltage. Frequency should be about 62 Hz; voltage about 122-126 volts AC.
- If frequency is high or low, adjust engine governor to obtain 62 Hertz at no-load; then recheck voltage reading.
- If frequency is good but voltage is high or low, adjust voltage regulator to obtain 124 volts at 62 Hz no-load.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 62 Hz no-load
- 122-126 volts AC no-load
- 124 volts at 62 Hz no-load
Full service-parts list: Generac NP-50G →, Generac NP-50LP →, Generac Q-40G →
Source: Generac service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.