Even indirect lightning can cause real damage to your property. Power surges can move through electrical lines in a split second, and your HVAC system is often one of the first things affected. From fried circuit boards to tripped breakers, the effects can sneak up on you fast. At Honest Air Conditioning, in Mesa, AZ, we’ve seen how storm season can knock out comfort and leave behind a hefty repair bill.
If you’re unsure what to do after a strike, start with this guide and take it one step at a time.
How Lighning Reaches Your HVAC System
When lightning hits nearby, the damage doesn’t always start with a crash. It often starts with a sudden surge of electricity that moves through power lines, cable systems, or even the ground itself. That spike enters your house and hits anything plugged in, including your HVAC system. Since your air conditioner connects directly to the home’s electrical panel, it sits in a vulnerable spot. The control board, capacitor, and compressor can all take the hit in seconds, without any outward sign of damage.
Your system might stop working immediately, or it could keep running with unseen damage. The surge doesn’t need to travel far. If your thermostat is calling for cool air at the exact moment lightning hits the grid, the jolt can burn out components inside the control board. That kind of electrical trauma rarely comes with a warning. One flicker, and the entire unit might go silent. In this case, you won’t just need AC repair, but possibly an electrical panel repair and other fixes as well.
What You’ll Notice After a Strike
The first clue often shows up at the thermostat. The display may be blank. It may turn on, but the system never kicks in. Sometimes, the fan hums, but cold air never follows. In milder cases, your system powers up, only to shut itself off within seconds. That can mean the internal sensors are out of sync or a capacitor failed during the surge.
More severe damage creates silence: no fan, no compressor, no air movement at all. In some cases, the circuit breaker trips and won’t reset. You might smell burnt plastic or notice a ticking sound from the unit. These symptoms might not show up right away. That delay makes it harder to connect the dots back to the storm, but if everything worked before the lightning, the timing matters.
Why the Control Board Takes the Hit First
The control board in your HVAC system is like the command center. It receives instructions from your thermostat, manages sensors, and activates key components. That board connects to both the high-voltage and low-voltage sides of the system, which puts it directly in the path of any electrical surge.
If the control board fries, your system can’t respond. Even a functional compressor or fan motor won’t activate if the board never sends the signal. Sometimes, the damage is partial. One relay might stick open. One circuit might burn. That kind of hit leaves your system acting confused, starting and stopping in weird patterns, or ignoring thermostat changes altogether.
Replacing the board doesn’t always fix the issue, either. If the surge passed through other components before reaching the board, additional failures might follow soon after.
What Happens to the Compressor
The compressor handles the heavy work in your cooling cycle. It pressurizes the refrigerant and pushes it through the coil. A surge can overheat its motor windings, lock the rotor, or short a terminal. If the compressor gets damaged, the system might blow warm air, cycle endlessly, or run loudly without delivering results.
In some cases, the compressor hums but never starts. That symptom points to a seized motor or blown capacitor. If it clicks and stops, you might have internal overload damage. Either way, a broken compressor usually means expensive repairs. When that component fails, the rest of the system loses its ability to cool.
Even if the compressor doesn’t break right away, its lifespan shrinks after any surge. That added strain makes it more likely to fail during the next stretch of high use.
Other Parts Might Suffer
Capacitors often follow the same fate as the board. They regulate voltage and store power to help motors start. A surge can blow them open or leak fluid, leaving the motors powerless. That causes either silence or a slow stuttering hum from the outdoor unit. You might also notice your indoor fan working while the outdoor unit stays dead.
Transformers, relays, and contactors can all take damage as well. These parts handle the flow of electricity and convert signals from one part of the system to another. After a strike, their coils might burn, or their switches may stick. If your system starts randomly or struggles to shut off, those pieces deserve a look. Sometimes, even the wiring gets damaged. Connections loosen, terminals melt, and insulation can split from the heat of the surge.
How a Surge Alters Performance Long-Term
Not all storm damage stops your system right away. Sometimes, it weakens the parts just enough to cause breakdowns later. A capacitor might work, but it’s not enough to start the motor on the third try. A sensor might send slightly off readings. That kind of wear throws off efficiency.
You might start hearing your system cycle more often. You might feel uneven temperatures from room to room. It takes more energy to cool the same space, and the thermostat readings may seem disconnected from how the room feels.
If those issues started after a lightning strike, chances are high that something small got damaged inside. These problems build slowly. You may think your system is just aging, but what really happened is that a surge knocked a few components off balance.
How to Check the System After a Storm
After a major storm, check your HVAC system like you would any other appliance. Walk to your thermostat and see if the screen looks normal. Try switching it to fan-only mode. If the blower does not start, the problem may go deeper than a tripped breaker.
Next, check the outdoor unit. If it’s silent while the fan inside is running, that split behavior suggests damage. Sometimes, the outdoor disconnect switch was thrown by the surge. Resetting that switch carefully can restore power, but only if the rest of the system is safe to run.
If your breakers trip more than once or if anything smells burnt, stop and call a pro. Resetting a breaker repeatedly on a damaged system can lead to bigger problems. Write down what worked and what didn’t before the technician arrives, especially if things behave differently than before the storm.
What Surge Protection Can and Can’t Do
Surge protectors help manage voltage spikes, but they are not perfect shields. A whole-house surge protector sits at your main panel and diverts sudden energy away from appliances. That added layer helps, especially for systems like HVAC that don’t plug into a surge strip.
Some systems also include internal surge protection at the outdoor unit. That small device can absorb brief spikes before they hit the compressor or board. However, in a direct strike, those may not absorb everything. They’re meant to reduce risk, not eliminate it.
The best defense combines layered protection. A surge protector at the panel, one at the HVAC system, and routine maintenance all work together. If you’ve never had protection before and lightning recently hit, now is a good time to consider it.
Call Us Today To Check Out Your HVAC System After a Lightning Strike
Your HVAC system keeps you comfortable, but it also runs on a network that doesn’t always handle lightning strikes well. If your system is acting strangely after a storm, don’t ignore the signs. A quick inspection from our heating and cooling service technicians could save you from more damage or a full replacement later. In addition to HVAC repair, Honest Air Conditioning offers surge protection services that help reduce your risk next time storms roll in.
Call Honest Air Conditioning today to get your system checked before a small issue becomes a big problem.