How to Diagnose & Replace Faulty Cables: A Complete Guide

Whether it’s your phone not charging, your screen flickering, or your internet dropping, a faulty cable is often the hidden culprit. Knowing how to diagnose and replace a cable can save you time, frustration, and even prevent hardware damage.

In this complete guide, we’ll walk you through:

• How to spot the signs of a faulty cable

• Step-by-step diagnosis methods

• Tools to test cables accurately

• When to repair vs. when to replace

• How to choose the right replacement cable

• Safety tips and expert recommendations

Let’s dive in.

Faulty cables often cause problems that can be mistaken for issues with the device or port itself. Recognising the early warning signs can help you catch issues before they become worse.

Your device only charges or works when the cable is held at a certain angle. This is usually a result of:

• Internal wire breakage

• Loose connection at the plug end

• Bent or worn connectors

This often indicates:

• Cable degradation over time

• Low-power cables used with high-demand devices

• A damaged or frayed charging wire inside

📌 Tip: USB cables vary greatly in quality. Some only transmit power, not data. Some support fast charging (18W, 60W, or 100W), while others do not.

If you hear crackling, buzzing, or see flickering or “no signal” errors, your AV cable may have:

• Poor shielding

• Connector corrosion

• Signal interference due to wear

If your devices fail to sync or transfer files, your USB, Thunderbolt, or Ethernet cable may be:

• Not rated for data transfer

• Internally damaged

• Using outdated standards (e.g., USB 2.0 instead of 3.0)

Always visually inspect your cable:

• Look for fraying, twists, splits, kinks, or melted sections

• Inspect the connectors for bent or missing pins

• Check for burn marks, which may indicate overheating

Here’s how to test your cable using both simple and advanced methods.

Use a functioning, same-type cable to test the same setup:

• If the problem disappears, the original cable is the issue.

• If the issue persists, the port or device may be the problem.

Use your cable on a different compatible device:

• If it works elsewhere, the cable is likely OK.

• If it fails across multiple devices, it’s likely faulty.

Plug the cable into the device and gently wiggle it near both ends:

• If the connection drops or flickers, internal damage is likely.

• This is common with phone charging cables and HDMI leads.

For Ethernet, HDMI, and more advanced cables, use a cable tester:

• Network testers can check for open wires, shorts, or cross-connections.

• HDMI testers check signal integrity and compliance with HDMI standards.

📌 Tip: If you’re frequently testing cables, consider investing in a multi-cable diagnostic tool.

In some cases, yes — but proceed with caution.

• Electrical Tape or Heat Shrink Tubing: For small cuts or nicks in the cable sheath.

• Re-soldering Connectors: If a wire is disconnected from a plug (only attempt if you’re comfortable soldering).

• DIY Cable Ends: Available for USB, HDMI, DC power jacks, and more.

• The cable is part of a power supply or AC adapter

• There is visible scorching or melting

• The cable is used with high-voltage or sensitive electronics

• You lack proper tools or experience

Here’s when it’s better to replace than repair:

When shopping for a new cable, consider the following:

• Connector Types: USB‑A, USB‑C, Lightning, HDMI, Ethernet, AUX, DisplayPort

• Device Support: Ensure it fits your laptop, smartphone, TV, router, or console.

• Shorter cables reduce signal loss and clutter.

• Braided cables are more durable and tangle-resistant.

• Look for strain relief at the plug ends for longevity.

📌 Pro tip: For charging setups, ensure the cable supports the voltage/wattage of your charger (especially important for USB-C PD).

• Unplug devices before inspecting or replacing cables.

• Don’t bend cables excessively or wrap them tightly.

• Replace any cable that feels hot to the touch.

• Don’t mix low-quality cables with high-performance equipment (e.g., cheap HDMI with 4K/8K setups).

• Digital Multimeter – Test continuity and voltage delivery

• Network Cable Tester – For Cat5e/Cat6 Ethernet cables

• HDMI Signal Tester – For AV installations

• Cable Organisers – Prevent tangling and breakage

Q: Can a faulty cable damage my device?

A: Yes. Short circuits or voltage drops can affect sensitive electronics.

Q: How often should I replace cables?

A: Cables used daily (e.g., phone chargers) may need replacing every 6–12 months, depending on usage and quality.

Q: Are braided cables really better?

A: Yes — they offer better resistance to wear and tearing and tend to last longer.

Explore Maplin's full range of Cables and Adapters today to find the ideal replacement for a faulty cable, or upgrade your existing cables with professional features such as Power Delivery (PD), gold-plated connectors and braided cables.