Allen Bradley MicroLogix 1400 “FAULT” Light Blinking Red? (Troubleshooting Guide)

Is your production line stopped because of a PLC failure? If you are seeing a Blinking Red “FAULT” Light on your Allen Bradley MicroLogix 1400 PLC, you are facing a common industrial automation issue. A fault in the PLC can halt the entire machine, causing heavy production losses.

At JRM Solutions (Noida), we understand the urgency. In this guide, we will help you identify the problem and fix it quickly.

Why is the FAULT Light Blinking?

The red blinking light on an Allen Bradley MicroLogix 1400 (Series 1766) usually indicates a “Recoverable” or “Non-Recoverable” error. The most common reasons are:

1. Low Battery: The internal battery that holds the program memory is dead.

2. I/O Module Failure: Short circuit in input/output wiring.

3. Program Glitch: A mathematical overflow or logic error in the ladder program.

4. Hardware Failure (Critical): The CPU or internal circuit board is damaged due to power surges or age.

Step-by-Step Solution to Fix the Error

Before calling a repair technician, try these 3 simple steps to reset the PLC:

Step 1: Power Cycle the Machine

The classic “Turn it OFF and ON again” works surprisingly well.

• Turn OFF the main 24V DC or 220V AC power supply to the PLC.

• Wait for 30 seconds (to let the capacitors discharge).

• Turn the power ON.

• Result: If the light turns Green (RUN mode), it was a temporary glitch.

Step 2: Check the “BAT” LED

Look closely at the PLC status LEDs. Is the “BAT” (Battery) light ON?

• Yes: Your PLC has lost its memory backup battery. Replacing the battery usually clears the fault.

• No: Proceed to Step 3.

Step 3: Go Online with RSLogix 500

Connect your laptop using the Ethernet or Serial cable and open the RSLogix 500 software.

1. Go “Online” with the processor.

2. Click on “Processor Status”.

3. Check the “Major Error Code”.

4. If the error code says “Hardware Fault”, it means the internal motherboard is burnt or damaged.

Still Not Working? The PLC Might Be Dead.

If you have tried the steps above and the Red Light is still blinking (or solid red), your MicroLogix 1400 is permanently damaged.

Repairing a burnt PLC motherboard is risky. It takes 7-10 days and often fails again within a month. Do not risk your factory production.

✅ The Best Solution: Replace It Immediately

We have Ready Stock of Brand New Allen Bradley PLCs in Noida. You can get your machine running Today.

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Product: Allen Bradley MicroLogix 1400 PLC Models Available:

• 1766-L32BXB (24V DC, Transistor Output) – Most Popular

• 1766-L32BWA (110/240V AC, Relay Output)

• 1766-L32BWAA (Analog Input/Output)

Condition: 100% Original | New Box Pack | 1 Year Warranty Price: Wholesale / Dealer Price (Lower than Market) Delivery: Same Day Dispatch via Bluedart / Hand Delivery in Delhi NCR.

📞 Contact JRM Solutions Now

Don’t wait for a repair technician. Install a new unit and start production immediately.

• Call / WhatsApp: +91 8766335023

• Email: sales@jrmsolutions.net

• Office Location: Noida Sector 64, Uttar Pradesh.

“We keep your machines running!”