The Ten Step Troubleshooting Process

This lesson focuses on a particular electrical failure that needs to be found and fixed. Rather than a typical Guess and Check, (sometimes known as Hit Or Miss) method, we will apply the Ten Step Troubleshooting Process, or TSTP.

The TSTP is a logical series of steps that can be adapted to nearly any troubleshooting problem, and followed for an efficient and effective equipment fix.

The Problem

You're a technician at a small gravel extraction company.

A loader with seemingly dead circuits has come in.

Earlier today, before the loader was brought in for repair...

The operator noticed that the hydraulic oil high-temperature warning light was on, and he stopped the machine and went for a coffee break. Afterward, when he restarted his machine, the light was off.

So, he resumed work.

The high temperature light soon came back on, and then went off almost immediately, along with the work lights and the lights in the operator's gauge cluster. The entire circuit seems to be dead.

Experience To The Rescue

This isn't your first day on the job, and you know exactly what these symptoms sound like - a blown fuse. Sure enough, when you check the fuse box, this circuit's fuse has obviously blown… violently.

It's easy to replace the fuse, but considering the scorch marks, the fuse almost certainly blew for a reason. It looks like there is a short somewhere in this circuit, and as long as it exists, replacement fuses will just blow as well. You're going to need to find and fix the short circuit - it's troubleshooting time!

Step 1
Define The Problem

Our loader problem is a textbook case of "No Go".

Specifically, it's almost certainly a short circuit. This will modify our troubleshooting process slightly.

Step 2
Consult Schematic & Gather Documentation

Before doing anything else, head to the bookshelf and grab the manual & schematics for this loader.

If you have a schematic that is up to date, and verified for accuracy, congratulations! You are miles ahead in troubleshooting this problem. An accurate and trustworthy schematic is the key to an electrical system; it can provide:

• A list of all of the components in the system, often including exact part numbers, codes and system-specific settings.
• A diagram of the relationships between system components.
• The exact location of test-points.
• Ways to isolate sub-circuits for testing purposes.

Scan Existing Documentation & Records

Review the shop records. Has this loader or others like it been in for repairs recently? Look for evidence of a recurring problem, or a maintenance-induced problem.

It looks like something was up with the same electrical circuit a few months ago; the fuse in this circuit was replaced 4 times in just a few weeks. There's no sign of problems since, though.

Step 3
List Suspect Components

Think of the ways each component could fail. Could that cause a no-go fault?

In this step, try to list failures that could cause any no-go fault, regardless of how likely it may be.

As you consider each component, ask yourself these questions:

• What is this component?
• What does it do?
• What can go wrong with it?
• Can that cause a no-go fault?