Cummins/Onan — Adjusting Voltage
Adjustments · genset controller / voltage regulator
From a Cummins/Onan service manual covering: 5.5 HGJAA, 5.5 HGJAB, 6.5 HGJAA, 6.5 HGJAB, 7.0 HGJAA, 7.0 HGJAB. Check it applies to your exact model before use.
Applies to: Cummins/Onan HGJAA, Cummins/Onan HGJAB
Before you start
- HAZARDOUS VOLTAGE! Touching uninsulated live parts can result in severe personal injury or death.
Procedure
- Make sure proper fuel, exhaust, and battery connections have been made and the engine has the proper level of oil.
- Disconnect all generator loads and connect accurate meters to measure AC volts and frequency.
- Start the genset and let voltage and frequency stabilize for 5 to 10 seconds.
- Rapidly press the control switch to START 6 times within 10 seconds.
- To adjust voltage up, press the control switch to START and release quickly (voltage rises approximately 0.6 volt each time).
- To adjust voltage down, press the control switch to START and release in approximately 2 seconds (voltage drops approximately 0.6 volt each time).
- Normal operation resumes 20 seconds after the last adjustment.
Tools required
- Meters to measure AC volts and frequency Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Each switch press changes voltage approximately 0.6 volt
- Voltage set mode: amber status lamp blinks once per second; green lamp remains on
- Voltage set mode entered by pressing START 6 times within the first minute after startup
Full service-parts list: Cummins/Onan HGJAA →, Cummins/Onan HGJAB →
Source: Cummins/Onan 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.