The Fault After a Storm: Decision Tree

Why this matters

A call that starts with "it worked fine until that storm last night" tells you more than the customer realizes. Weather concentrates a few specific failure modes: surges through the power line, water where it does not belong, wind loosening or striking something, and a power outage that left equipment in a bad state on restart. If you walk in assuming a normal random failure, you will chase the wrong part. Start from the storm and the cause narrows fast.

Start here: what did the storm actually do

Before touching the equipment, ask three quick questions and look around.

• Did the power go out? If yes, you are looking at a surge on restoration or a control that did not recover cleanly.
• Is there visible water, or was there? Check for staining, drips, mud lines, and damp insulation near the unit.
• Did wind move or hit anything? Look for displaced panels, downed limbs, bent vents, and debris against outdoor equipment.

The answers tell you which branch to walk first. Most storm faults are one of four families: surge, water, physical, or a bad restart.

Branch 1: lost power, dead or erratic on return

A grid surge or the inrush when power snaps back is the most common storm killer of electronics.

• If the unit is completely dead: check the simplest thing first. Confirm the breaker did not trip and any GFCI or in-line fuse is intact. Reset a tripped breaker once. If it trips again immediately, stop. You have a fault downstream, not a nuisance trip.
• If power is present at the equipment but it will not start: suspect a surge-damaged control board or low-voltage transformer. Look for scorch marks, a swollen capacitor, or a blown surge protector on the board.
• If it starts but behaves strangely (wrong mode, error code, frozen display): the controller likely powered up mid-cycle and is confused. Cut power fully for a minute, then restore it. A clean restart clears many of these. If the fault returns, the board took damage.

Branch 2: water got in

Water and electricity is the obvious risk, but water also causes slower failures: corrosion, swollen materials, and shorted low-voltage runs.

• If you see standing water on or in the equipment: kill power before you touch anything conductive. Do not energize wet electronics.
• If a low-voltage circuit is acting up (sensors reading wrong, intermittent operation): look for a wet connection or a control wire whose insulation got soaked. Even clean water bridges low-voltage contacts and creates false signals.
• If everything looks dry now but the fault is intermittent: moisture may have wicked into a connector and is drying unevenly. Open suspect connections, dry them, and treat with an appropriate electrical contact cleaner. See related: Moisture: The Universal Enemy.

Branch 3: wind, impact, or debris

Physical storm damage is the easiest to confirm because you can see it, but the visible damage is not always where the symptom shows up.

• If a panel, cover, or vent is displaced: check what it was protecting. An exposed control, a kinked line, or a fan that now hits its housing.
• If a fan or blade will not spin or runs rough: look for a bent blade, a lodged stick, or a guard pushed into the path. Clear it and spin by hand before powering up.
• If a line, hose, or duct was struck: trace it end to end. A partial crush restricts flow without an obvious leak.

Branch 4: it ran through the storm and degraded

Sometimes nothing dramatic happened, but the equipment ran hard under storm conditions (a flooded condensate path, an overloaded sump, a system fighting extreme load) and something gave out from stress rather than a single event. Treat this as a normal failure of the most-stressed component, and check whether the storm overwhelmed a drain, a pump, or a cooling path.

When to stop and protect yourself

If you find energized water, a burning smell, scorched conductors, or a breaker that trips on reset, de-energize and isolate before going further. Storm-damaged wiring can be live in unexpected places. Document what you find with photos, since storm damage is frequently an insurance claim.

References

• OSHA guidance on electrical safety and working near water-damaged equipment.
• NFPA 70 (National Electrical Code) on surge protection and grounding principles.
• Manufacturer documentation for restart and reset procedures after a power loss.
• See related: Moisture: The Universal Enemy; Why Electrical Connections Degrade.