Kohler APM402

Theresa HarrisOct 24, 2025

How to fix a faulty Kohler APM402?

T
Taylor JonesOct 24, 2025
If the Kohler Controller master control button is in the OFF/RESET mode, press the controller master control RUN or AUTO button. In case of controller circuit board(s) inoperative, controller master control buttons inoperative, replace the controller or the controller master control button circuit board. If the controller fuse is blown, check for continuity across the fuse and troubleshoot the controller wiring and replace the circuit board, or if the voltage regulation is inoperative, replace the junction box sensing fuses. For a controller firmware error, review the controller display troubleshooting chart. If the engine start circuit is open, press the controller master control RUN button to test the generator set and troubleshoot the auto start circuit and the time delays. In case of c...

Model	APM402
Type	Controller
Communication Protocol	Modbus RTU
Input Voltage	24 VDC
Output	Relay
Voltage	24 VDC

Model

APM402

Type

Controller

Communication Protocol

Modbus RTU

Input Voltage

24 VDC

Output

Relay

Voltage

24 VDC

Summary

Safety Precautions and Instructions

General Safety Warnings

Covers essential safety warnings including accidental starting, battery, explosion, engine, and voltage hazards.

Section 1. Specifications and Features

Controller Features Overview

Details controller components like display, lamps, switches, and connections for operation.

Controller Logic Specifications

Outlines controller logic specifications, including status events, faults, and voltage regulator details.

Section 2. Operation

Prestart Checklist

Essential checks and inspections before starting the generator set for satisfactory operation.

Controller Operation

Explains controller functions for starting, stopping, status indications, and fault handling.

Menu Displays and Navigation

Summarizes controller menu displays, data types, and navigation using the pushbutton/rotary dial.

Error Messages and Diagnostics

Lists and explains controller error messages and diagnostic information for troubleshooting.

Section 3. Scheduled Maintenance

Service Schedule

Provides a detailed schedule for visually inspecting, checking, changing, cleaning, and testing system components.

Fuel System Maintenance

Covers maintenance for diesel and gaseous fuel systems, including bleeding air and system concepts.

Battery Maintenance

Details battery cleaning, electrolyte level inspection, specific gravity checks, and charging procedures.

Storage Procedures

Outlines procedures for storing the generator set, including lubrication, cooling, fuel, and engine components.

Section 4. General Troubleshooting

Troubleshooting Charts

Provides charts to diagnose and correct common generator set problems and controller display issues.

Section 6. Accessories

Accessories and Connections

Describes various accessories that enhance generator set functionality and installation compliance.

Accessory Connections

Details terminal connections for controller accessories, including inputs, outputs, and power connections.

Table of Contents

Questions and Answers:

Kohler APM402 Specifications