5 Red Flags That Indicate Solar Power Cable Trouble

Solar power cables, also known as photovoltaic (PV) cables, are the lifelines that link panels in PV systems to inverters, batteries, and the rest of the system, carrying the electricity generated by the array to where it’s needed. But like all PV components, these cables aren’t immune to wear and tear, especially under Australia’s tough environmental conditions.

When cables start to fail, at best system efficiency drops; worst case they damage or short-circuit the system, which can lead to dangerous electrical fires. It’s essential for technicians to be able to identify potential signs of a solar power cable that seems at risk of failing and address the issue before it spirals into something larger.

So, what are the telltale signs you should look for? Here are five key red flags to keep in mind and what to do if you notice them.

Sign #1: Cracked or Damaged Insulation

Insulation is the first line of defence for any solar power cable. If you notice cracks, splits, or brittle sections, it’s a sign that the sheath has likely degraded. UV radiation breaks down polymers over time, while constant heating and cooling causes rapid expansion and contraction that can weaken the cable jacket.

Once the inner conductor is exposed, the risk of moisture ingress, corrosion, or accidental contact rises sharply. Electricity flowing through a compromised path also loses efficiency and poses a greater risk of shock.

Solution:

• For small cracks, apply heat-shrink tubing to restore protection and keep the repair compliant with AS/NZS 3000.
• For significant damage, replacement is the only safe option. Remove the affected section and join the new cable using approved connectors.

Sign #2: Discolouration or Burn Marks

Darkened insulation, scorch marks, or melted spots on a solar power cable are signs that point to overheating. This often happens when cables are undersized for the current they carry or when attached MC4 connectors loosen over time. Both scenarios create excessive resistance, which in turn generates heat.

Left unchecked, overheating can compromise insulation and, in extreme cases, ignite surrounding materials. It’s one of the most serious cable-related hazards in solar power systems.

Solution:

• Before replacing the damaged cable, isolate the system.
• Select a replacement cable with the correct current-carrying capacity, factoring in cable length and voltage drop.
• Don’t overlook the connectors and junction boxes. A faulty MC4 connector or improperly crimped lug may be the real source of excess heat. If this is the case, replace as necessary.

Sign #3: Loose or Exposed Cabling 

Untidy cable runs don’t just look unprofessional; they wear out faster. Unsecured solar power cables can rub against roof tiles, gutters, or sharp edges in high winds, stripping away vital insulation.

Prolonged exposure to direct sunlight without shielding also accelerates cracking in the insulation, while wildlife such as possums and birds are often tempted to chew or peck at dangling cables.

Solution:

• Secure all runs with UV-rated cable ties, clips, or solar ducts to prevent movement.
• If cables are already frayed, replace them and consider re-routing for better protection.
• Bundle cables neatly along structured pathways, as good cable management improves durability and gives the installation a polished, professional finish.

Sign #4: Moisture or Corrosion 

Water and electricity are a dangerous combination. Rain, humidity, or salty sea air can enter cables through damaged sheaths or poorly sealed connectors like MC4 connectors. Once moisture gets inside, corrosion sets in, weakening conductivity and creating the perfect conditions for short circuits. Coastal cable installations are particularly vulnerable to this.

Solution:

• For mild corrosion on connectors, remove them and clean using a corrosion-resistant solution, then rinse and dry thoroughly before reconnecting.
• Replace any heavily corroded cable sections immediately, and always double-check that connectors are watertight.
• In high-risk environments, use tinned copper conductors for their superior corrosion resistance. Gel seals and conduits provide additional protection.

Sign #5: System Underperformance

Sometimes, the warning signs aren’t immediately visible. If a PV system’s output drops unexpectedly despite clean panels and good sun exposure, faulty cabling may be to blame. Voltage drops, lower energy harvests and arcing can all be caused by micro-cracks, breaks, or poor terminations that are hard to spot at first glance.

Solution:

• Perform electrical testing of continuity, voltage, and insulation resistance. Compare results with the manufacturer’s specifications.
• Replace any underperforming cable and re-test the system to confirm restored output.
• Regular maintenance is key, as these hidden issues are often caught only through systematic testing.

Best Practices for Healthy Solar Power Cabling

While recognising red flags is important, the best approach to maintaining good cable health is prevention. Well-chosen, properly installed, and regularly maintained cabling can significantly reduce the risk of faults occurring and extend the system’s lifespan.

1. Choose the right cables at installation

Not all electrical cables are suitable for PV systems. Always use solar-rated cables that meet AS/NZS 3000 standards. These are engineered for high UV exposure, wide temperature ranges, and mechanical stress. In coastal or tropical regions, tinned copper conductors are highly recommended for superior corrosion resistance.

2. Size cables correctly

Cables that are too small for the system’s current lead to overheating and wasted energy. Before installation, calculate cable size based on maximum continuous current, cable run length, and allowable voltage drop. Correct sizing ensures safe operation and higher efficiency.

3. Prioritise environmental protection

Australian roofs are unforgiving. Conduits, trunking, and UV-rated ties provide a shield against sunlight, abrasion, wind, and wildlife. Positioning cables away from sharp edges and moving parts minimises the chance of damage over time.

4. Follow neat cable management

Organised runs aren’t just about appearance. Neatly secured cables reduce strain on connectors, prevent tangling, and make future maintenance easier. Installers who prioritise cable management also signal quality workmanship to their clients.

5. Schedule regular inspections

Annual or biannual inspections help detect early signs of wear before they escalate. Look for cracks, brittleness, loose connectors, or corrosion. Supplement visual checks with electrical tests – continuity, insulation resistance, and voltage drop – to identify hidden issues.

6. Document and maintain records

Documenting every inspection, test, and replacement creates a valuable maintenance history. Over time, these records highlight patterns of wear, helping technicians predict and address issues proactively rather than reactively.

By embedding these best practices into everyday work, technicians can safeguard both system performance and safety. Preventive action is always less costly than emergency repair.

Reliable Systems Start with Reliable Cables

Solar power cables may not be the most prominent component of a PV system, but they are among the most critical. Cracked insulation, burn marks, loose or exposed runs, corrosion, and unexplained underperformance all signal trouble and should be addressed without delay.

While being able to spot warning signs of failing cables is important, prevention is always better than cure. The first step starts with making quality component choices at installation. To ensure your systems are efficient, safe, and built to last, always partner with a trusted supplier who understands your needs and delivers high-quality, compliant solar cables for reliable installations.