Kohler G120 Automatic Transfer Switches Service and Parts Manual (tp5992)

These Kohler G120 automatic transfer switches live in electrical rooms, plant rooms, and outdoor enclosures, quietly handling the handoff between utility power and your generator. This service and parts manual helps you match every bracket, relay, lug kit, and harness in that cabinet to the right Kohler part number before you order. When you’re chasing a nuisance transfer issue and have the switch gutted on the wall, this book lets you identify exactly which contactor assembly or control board you’re looking at so you don’t guess and buy the wrong piece.

Applications & Use Cases

• Tracing assemblies from the front door label down to the correct internal subcomponents before a repair.
• Verifying replacement parts during a teardown so every screw, shroud, and terminal strip goes back with the proper Kohler-numbered item.
• Comparing design changes between older and newer G120 builds to see which parts still interchange.
• Confirming accessory kits (aux contacts, communication modules, etc.) match the switch rating and configuration on site.
• Documenting what was changed for maintenance records by tying field notes to exact part numbers.

FAQ

Q: Can I use this manual on a tablet while I’m at the switchgear lineup?

A: Yes, it works well digitally; you can zoom in on the diagrams and search part descriptions instead of flipping paper pages.

Q: Is it worth printing sections of this manual?

A: Many techs print the relevant parts pages for a specific switch and keep them in a job folder to avoid getting a full manual dirty.

Safety Note

Always isolate and verify all power sources are de-energized before opening or servicing the transfer switch enclosure.

Kohler G120 Automatic Transfer Switches Index:

Safety Precautions and Instructions
Introduction
List of Related Materials
Service Assistance
Service Information
Product Information

Section Specifications
Purpose
Components
Nameplate
Model Number
Specifications
Ratings
Application Data

Section Operation
Startup
Automatic Operation
Failure of Normal Power
Restoration of Normal Power
Exerciser Function
Exerciser Switch
Exerciser Power Requirements
Manual Operation
External Test Switch

Section Scheduled Maintenance
Inspection and Service
General Inspection
Internal Inspections Procedures and Tests
Testing
Weekly Generator Set Exercise
Monthly Automatic Operation Test
Other Tests
Service Schedule

Section Troubleshooting
General Notes on Connections
Power to the System
AC System Voltages
DC Controller Voltages
Engine Start Circuit
Exerciser Circuits
Contactor Operation
Mechanical Check
Initial Solenoid and Rectifier Troubleshooting
Solenoid Test
Rectifier Test
After Solenoid Replacement
Coil Clearing Contacts
NR/ER Relays and Controller Circuitry

Controller Operation
Emergency Source Sensing
Normal Source Sensing

Section Diagrams

Section Service Part Replacement
Before and After Servicing Components
Contactor Assembly
Contactor Assembly Removal
Contactor Assembly Installation
Solenoid Assembly
Solenoid Assembly Removal
Solenoid Assembly Installation
Controller PCB Assembly
Controller PCB Removal
Controller PCB Installation
Other Service Parts
Other Service Part Removal
Other Service Part Installation

Section Service Parts
General Information
Finding Parts Information
Leads
Common Hardware
Contactor
Controls
Decals
Enclosure
Neutral Lug

Appendix Abbreviations
Appendix Common Hardware Application Guidelines
Appendix General Torque Specifications
Appendix Common Hardware Identification
Appendix Common Hardware List

Kohler