Solar Fault Finding Flowchart

A solar system has only a few places it can fail. The challenge is working through them in the right order, because some failures look like others, and some checks are dangerous if done out of sequence. This is the diagnostic flow used on a Solar Health Check.

Work through the steps in order. Each step is non-invasive: observation only, no disconnection, no opening of equipment. If you reach a step that requires opening covers, isolating circuits, or testing live components, stop. That’s licensed work.

Step 1: Is the inverter on?

Look at the inverter screen.

• Screen is on, no fault. Go to step 2.
• Screen is on, fault code visible. Note the code. Look it up against the brand’s fault list (see Reading Your Inverter Fault Codes). Most fault codes either clear themselves or require a solar electrician.
• Screen is off entirely. The inverter has lost both AC and DC. Check the AC isolator on the wall next to it (often labelled “Inverter AC isolator”). Check the DC isolator on the roof or near the inverter. If both isolators are on and the screen is still dead, the inverter has failed and needs replacement or warranty service.
• Screen is dim or flickering. Internal power supply failure. Service call.

Step 2: Is the system producing power right now?

Check the monitoring app or portal. Compare current production to what it should be doing at this time of day in this weather.

A rough rule for clear-sky midday production on a north-facing array:

• 6.6 kW system should produce 4.5–6 kW at midday in summer
• 10 kW system should produce 7–9 kW at midday in summer
• Winter midday is typically 60–70% of summer peak production

If current production is materially less than expected, you have a real problem. If it’s broadly in line, the issue may be intermittent. Go to step 4 and review the production history.

Step 3: Is monitoring still working?

Sometimes the system is producing. You just can’t see it. Symptoms:

• Monitoring app shows “0 W” but the inverter screen shows production
• App shows yesterday’s data but nothing today
• Login fails or the portal redirects you to set up a new account

This is the cheapest possible fix. The Wi-Fi password may have changed, the original installer’s account may have been deactivated, or the inverter’s data card may have failed. Reconfigure the Wi-Fi connection per the manufacturer’s app instructions. If that doesn’t work, the fault is in the inverter’s communication card, separate from the inverter itself, sometimes replaceable as a service part.

Step 4: How does production today compare to history?

Open the monitoring portal and look at production graphs over the past 7 days, 30 days, and 12 months. You’re looking for one of three patterns.

Pattern A: Sudden cliff

Production was normal until a specific date, then dropped sharply or stopped. The cause is something that happened on or near that date: a storm, electrical work in the house, a grid event, or component failure. Check the inverter fault log for that date.

Pattern B: Gradual decline

Production has been slowly dropping over months or years. Common causes:

• Panel soiling (bird droppings, dust, leaf litter)
• Panel degradation beyond the normal 0.5%/year
• Cell-level damage from microcracks (often invisible to the eye, visible to thermal imaging)
• One panel or string degraded faster than others, dragging the rest down

Pattern C: Intermittent disconnects

Production looks normal but with regular gaps. Usually grid voltage exceeds the inverter’s tolerance band on summer afternoons. The inverter is doing its job, protecting itself and the grid. Solution is volt-watt response configuration or battery storage, not inverter replacement.

Step 5: Check the panels visually

From the ground, with binoculars if needed. Look for:

• Panels that look noticeably different from their neighbours (discolouration, browning, cell-level damage)
• Bird droppings, particularly cockatoo or possum damage to cabling at the eaves
• Lifting or detached panels (rare but happens after cyclonic events)
• Junction box discolouration on the back of the panel (visible from below if you’re under an elevated array)

Don’t climb on the roof. Solar panels are fragile, the roof structure may have hidden weaknesses, and any fall is a long one.

Step 6: Check the switchboard

Look at the solar circuit breaker in your main switchboard. It should be labelled “Solar” or “Inverter.”

• Breaker tripped (in the off position). Reset it once. If it trips again immediately, do not reset a second time. There’s a fault and a solar electrician is needed.
• Breaker on but no production. The fault is downstream of the breaker, likely in the inverter, isolators, or DC side.

Step 7: Stop and call

If you’ve reached this point and the system isn’t working, the next step requires testing of live DC and AC circuits. That’s licensed work. A Solar Health Check is the right next step. Pricing starts from $250 in Zone 1, see the pricing page for the full zone breakdown. The Health Check covers all the testing required to identify the fault, and produces a written report and repair quote.

What the Health Check adds beyond what you can do yourself:

• DC string voltage and current testing
• Insulation resistance testing per AS/NZS 5033
• Inverter fault log download (if accessible) and review
• AC voltage and frequency testing under load
• Thermal imaging of panels and connections (where suspected)
• Photo documentation of the fault for warranty or insurance claims

When not to bother diagnosing

Three cases where the diagnostic spend isn’t justified:

• System older than 12 years with multiple suspected faults. Often more economical to replace the system than chase repairs.
• Original installer has gone bankrupt and the warranty is in dispute. Coordinate with manufacturer warranty support directly first.
• Solar was sold to you cheaply and the panels are no-name brands no longer imported. Replacement panels may not be available; new system is the realistic path.

Common questions

Can you do this without coming on site? Sometimes. Remote review of monitoring data and fault codes can identify around 30% of issues. The other 70% need physical testing.

My system is under warranty. Should I call the manufacturer first? If the original installer is still in business, call them. They lodge the warranty claim. If the installer is gone, the manufacturer may still honour the panel warranty (typically 25 years) or inverter warranty (5–10 years), but you’ll need to coordinate it. The Health Check report gives you the documentation to support the claim.

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