Fanuc Teach Pendant Not Working – Complete Checklist

Problem Overview

A Fanuc teach pendant not working is one of the most disruptive issues in daily robot operation. When the pendant fails, engineers cannot jog, teach, or recover the robot, often bringing the entire cell to a standstill.

In field service experience, most teach pendant failures are not caused by software, but by power, cable, or hardware-related issues. This checklist is designed to help engineers quickly isolate the root cause.

Typical Symptoms

You may encounter one or more of the following:

• Teach pendant does not power on

• Blank or black screen

• Pendant powers on but freezes

• Touchscreen not responding

• Emergency stop fault triggered

• Pendant disconnects when the cable is moved

Each symptom points to a different failure path, which is why a step-by-step checklist is critical.

Quick Safety Check (Before Anything Else)

Before troubleshooting:

• Ensure the robot is in a safe state

• Follow site lockout/tagout procedures if required

• Never bypass emergency stop circuits

Loss of pendant control can be a safety-critical condition.

Step 1: Check Pendant Power

Start with the simplest checks:

• Is the pendant completely dead (no LEDs, no screen)?

• Does the screen flicker briefly when powered?

Likely causes:

• No power from controller

• Internal power failure in the pendant

• Broken conductors in the pendant cable

If there is absolutely no response, the issue is usually power or cable related.

Step 2: Inspect the Teach Pendant Cable

The teach pendant cable is statistically the most common failure point.

Check for:

• Cuts, flat spots, or crushed sections

• Hardened or brittle outer jacket

• Damage near strain reliefs

• Intermittent behavior when the cable is moved

If the pendant disconnects or reboots when the cable is flexed, internal wire fatigue is very likely.

Step 3: Check Controller-Side Connection

At the controller cabinet:

• Ensure the pendant connector is fully seated and locked

• Inspect pins for bending or contamination

• Check for oil or dust ingress

A loose or partially seated connector can cause random disconnects and freezes.

Step 4: Emergency Stop and Enabling Device Check

Fanuc teach pendants route safety signals through the pendant assembly.

Verify:

• Emergency stop button is released and functional

• Enabling (deadman) switch clicks and returns normally

A faulty E-stop circuit can prevent the pendant from becoming operational, even if the screen powers on.

Step 5: Try a Known-Good Pendant or Cable

If available, swap components:

• Test the pendant with a known-good cable

• Test a known-good pendant on the same controller

Results interpretation:

• New pendant works → original pendant faulty

• New cable works → original cable faulty

• Neither works → controller-side issue

This isolation step can save hours of unnecessary diagnostics.

Common Root Causes (Ranked by Frequency)

Based on field data:

1. Teach pendant cable internal break

2. Strain relief failure near the pendant handle

3. Emergency stop circuit fault

4. Teach pendant hardware failure

5. Controller I/O or power supply issue

In most real-world cases, the cable is replaced first.

When Software Is (and Is Not) the Problem

Software-related causes are relatively rare.

Software may be involved if:

• Pendant works but displays boot or application errors

• Issue appeared immediately after a system update

Software is unlikely if:

• Pendant is completely dead

• Behavior changes when moving the cable

Avoid reloading software until hardware causes are ruled out.

Replacement Guidance

If troubleshooting confirms hardware failure:

• Replace the teach pendant cable if intermittent or damaged

• Replace the pendant if it fails on multiple systems

Key considerations:

• Correct model compatibility

• Verified pinout and shielding

• Reliable strain relief design

Using low-quality replacements often leads to recurring intermittent faults.

Preventive Tips from the Field

To reduce future failures:

• Avoid tight bends near the pendant handle

• Hang the pendant when not in use

• Do not trap the cable in cabinet doors

• Replace cables at the first sign of intermittent behavior

Teach pendant downtime is usually preventable with basic handling discipline.

Final Checklist Summary

Before escalating the issue, confirm:

• Power presence at the pendant

• Cable integrity under movement

• Secure controller connection

• Functional emergency stop and enabling switch

Most Fanuc teach pendant not working cases are resolved by systematically following these steps.

If the issue persists after completing this checklist, the problem may lie in the controller or safety circuit and requires deeper system-level diagnostics.