Product Manual
Table Of Contents
- Table of Contents
 - Safety
 - General Information
- Specifications
 - Unit Serial Number Locations
 - Component Locations
 - Control Panel
 - Power Zone™ Gen Controller
- Controller Features and Functions
 - Operator Screens
 - Alarm Mute
 - Auto/Manual Mode
 - Navigation Buttons
 - Control Power Switch
 - Engine Start
 - Engine Stop/Reset
 - The Liquid Crystal Display (LCD)
 - Operator Screens
 - Home Screen
 - Engine Screen
 - Generator Screen
 - Voltage Adjust Screen
 - Maintenance Screens
 - Generator Summary
 - Engine Tab
 - Generator Tab
 - Alarms Tab
 - Input/Output Tab
 - Schedule Tab
 - Status Tab
 - Generator Monitoring
 - Engine Monitoring
 - Controller Information Displays, Functions and Reset
 
 - Belt Tensioners
 
 - Operation
- Prestart Checklist
 - Manual Starting of the Unit
 - Auto (Remote) Starting of the Unit
 - Derating for Altitude
 - Generator Output Connection Lugs
 - Fine Voltage Adjustment
 - Voltage Selector Switch
 - Voltage Regulation
 - Customer Convenience Receptacles
 - Main Circuit Breaker
 - Exhaust Filter Cleaning Operations
 - Transfer Switch
 - Auto Exercise Timer
 - Shutting Down the Unit
 - Emergency Stop Switch
 - Idle Switch (MMG25I-45I only)
 - Towing the Unit
 - Lifting the Unit
 
 - Maintenance
- Emissions Information
 - Daily Walk Around Inspection
 - General Maintenance
 - Basic Maintenance Schedule - Isuzu Engine
 - Basic Maintenance Schedule - John Deere Engine
 - Isuzu Engine Break-In Requirements
 - John Deere Engine Break-In Requirements
 - Resetting the Maintenance Alarms
 - Checking Generator Drive Plate Torque
 - Jack Maintenance
 - Trailer Wheel Bearings
 
 - Troubleshooting
 - Wiring Diagrams
- AC Wiring - MMG25IF4, MMG45IF4
 - AC Wiring - MMG35DF4, MMG55DF4
 - AC Wiring - 4 Pos. Voltage Selector Switch Option - MMG25IF4, MMG45IF4
 - AC Wiring - 4 Pos. Voltage Selector Switch Option - MMG35DF4, MMG55DF4
 - AC Wiring Option - Standard Receptacles
 - AC Wiring Option - Engine Heater
 - AC Wiring Option - Buck Transformer
 - AC Wiring Option - PMG
 - DC Wiring
 - Trailer Lights Wiring
 - Wiring Harness - Electric Brake Option
 - DC Wiring Option - 12V Battery Charger
 - DC Wiring Option - Low Oil Level
 
 - Options & Accessories
 
Safety
36949 B MMG25I-35D-45I-55DF4 Operating Manual 3
• DO NOT start the unit under load. The circuit breakers must be in the OFF (O) position when starting 
the unit in Manual mode. The circuit breakers can be in the ON (I) position only when started in the 
Auto mode. A transfer switch must be used in the Auto mode to deflect the load upon startup.
TOWING SAFETY
Towing a trailer requires care. Both the trailer and vehicle must be in good condition and securely fastened 
to each other to reduce the possibility of an accident. Some states require that large trailers be registered 
and licensed. Contact your local Department of Transportation office to check on license requirements for 
your particular unit.
• Verify the hitch and coupling on the towing vehicle are rated equal to, or greater than, the trailer's 
Gross Vehicle Weight Rating (GVWR). 
• Check trailer tires for wear and proper inflation.
• DO NOT tow trailer using defective parts. Inspect the hitch and coupling for wear or damage. 
• Verify the trailer hitch and the coupling are compatible. Make sure the coupling is securely fastened 
to the vehicle.
• Verify directional and brake lights on the trailer are connected and working properly.
• Verify wheel lug nuts are present and tightened to the specified torque.
• Maximum recommended speed for highway towing is 45 mph (72 km/h). Recommended off-road 
towing speed is 10 mph (16 km/h) or less, depending on terrain.
• When towing, maintain extra space between vehicles and avoid soft shoulders, curbs and sudden 
lane changes. Practice turning, stopping and backing up in an area away from heavy traffic prior to 
transporting the unit. 
• Wipe the coupler clean and apply fresh grease each time the trailer is towed to eliminate squeaking.
• Connect safety chains in a crossing pattern under the tongue and ATTACH THE BREAKAWAY 
CABLE TO THE REAR BUMPER OF THE TOWING VEHICLE. Do not attach the cable to the trailer 
hitch.
• Before towing the trailer, verify that the weight of the trailer is equal across all tires. On trailers with 
adjustable height hitches, adjust the angle of the trailer tongue to keep the trailer as level as possible. 
On units equipped with a tandem axle trailer, a large angle between the trailer and tow vehicle will 
cause more weight to be carried by one axle, which could cause premature wear on the tires and 
axles and cause potentially unsafe operating conditions.
• The trailer is equipped with hydraulic or electric surge brakes. Verify proper operation of the brakes 
by braking the vehicle at a slow speed before entering traffic. Both the trailer and the vehicle should 
brake smoothly. If the trailer seems to be pushing, verify the level in the brake fluid reservoir, if equipped.
REPORTING TRAILER SAFETY DEFECTS
If you believe your trailer has a defect which could cause a crash or could cause injury or death, you should immediately 
inform the National Highway Traffic Safety Administration (NHTSA) in addition to notifying Generac Mobile Products.
If NHTSA receives similar complaints, it may open an investigation; and if it finds that a safety defect exists in a group 
of vehicles, it may order a recall and remedy campaign. However, NHTSA cannot become involved in an individual 
problem between you, your dealer, or Generac Mobile Products.
To contact NHTSA, you may either call the Auto Safety Hotline toll-free at 1-888-327-4236 (TTY:1-800-424-9153), 
go to http://www.safercar.gov; or write to:
Administrator
NHTSA
1200 New Jersey Avenue S.E.
Washington, DC 20590










