Why won’t my pool heater turn on — and where should I start troubleshooting?

There’s nothing more frustrating than walking out to your pool, hitting the power button, and realizing your heater just won’t start. No clicks. No heat. Just cold water and confusion.

Before you panic or assume it’s a major repair, take a breath — most heater issues start with something simple. Pool heaters rely on a few key systems working together: power, water flow, sensors, and safety switches. When one of these is off, your heater shuts itself down to protect the equipment.

At Pool Supply Depot, we see this all the time. In most cases, a few basic checks can get your system back up and running without a service call. Let’s go step by step through the five most common reasons your pool heater won’t turn on — and what you can do about each.

1. Low Water Flow or Dirty Filtration

If your heater won’t fire up, the first thing to check is water flow. Heaters are designed to shut off automatically when water isn’t circulating properly. It’s a safety feature that prevents overheating or damage.

Low flow can happen when:

• Your pool filter is clogged.

• The pump basket is full of debris.

• A valve is partially closed.

In Nevada’s dusty desert climate, filters can clog faster than expected — especially after a storm or a few windy days.

Try this first:
Turn off the heater and pump, clean your filter and pump basket, then restart your system. If you hear the heater click on after the flow improves, you’ve found the culprit.

At Pool Supply Depot, our technicians say this simple fix solves nearly half the “heater won’t start” calls they get.

2. Gas or Power Supply Problems

If your pool heater runs on gas (natural gas or propane), check your fuel supply and connections. If it’s electric, start with your breaker panel.

For gas heaters:

• Make sure the gas valve is open.

• Check that your propane tank isn’t empty.

• Inspect for any kinks or damage in the line.

For electric heat pumps:

• Confirm the breaker hasn’t tripped.

• Test if the outlet or control panel has power.

It might sound obvious, but it’s easy to overlook. Pool Supply Depot’s service team often finds heaters that “failed” were simply disconnected from power or had an empty propane tank.

Try this: Flip your breaker off and back on, and make sure gas valves are fully open. If you smell gas or suspect a leak, shut everything off and call a licensed professional immediately.

3. Faulty Ignition or Sensor Issues

If your heater powers on but doesn’t ignite, the issue might be within the ignition sequence. Modern heaters have several sensors that ensure safe operation — including flame detectors, temperature sensors, and pressure switches. If any of these malfunction, your heater won’t light.

Nevada’s hard water can add to the problem. Over time, calcium buildup can coat sensors and connectors, making it harder for them to read properly.

What to look for:

• Clicking sounds without ignition.

• Flashing error codes on your heater’s display.

• Rust or white calcium buildup near the ignition assembly.

You can gently clean sensor contacts if visible corrosion exists, but don’t disassemble the unit unless you know what you’re doing. Faulty sensors or igniters are inexpensive parts but should be handled by a professional to avoid damaging your control board.

4. Weather, Ventilation, or Installation Problems

Sometimes the problem isn’t inside the heater — it’s around it.

Wind: Strong gusts can blow out pilot flames or disrupt airflow sensors.
Ventilation: A blocked exhaust or intake can cause your heater to shut down automatically.
Placement: If your heater is installed too close to a wall or under a covered patio, trapped heat can trigger internal safety switches.

This is especially common in Nevada’s high-wind areas like Henderson or Pahrump.

Try this:
Inspect the area around your heater. Clear any debris from vents, make sure nothing’s covering the unit, and ensure it has at least three feet of clearance on all sides. Never operate your heater if it’s been recently covered or if exhaust gases can’t escape freely.

5. Internal Damage or Component Failure

If you’ve checked everything else and your heater still won’t start, there may be an internal issue — like a bad control board, relay, or water pressure switch. These aren’t DIY repairs, but they’re not always a full replacement either.

Many homeowners assume a non-working heater means it’s “dead,” but Pool Supply Depot’s technicians regularly repair heaters with simple part swaps. We carry replacement components from trusted brands like Pentair, Hayward, Jandy, and Raypak, so you can replace what’s broken — not the whole system.

If your heater is more than 8–10 years old, though, it might be worth comparing repair costs to a new, more efficient model.

What if I’ve tried everything and my pool heater still won’t turn on?

If you’ve cleaned the filter, checked the gas or power, and confirmed ventilation — and it still won’t fire — it’s time to call in an expert.

Attempting electrical or gas repairs without proper experience can be dangerous and may void your warranty.

At Pool Supply Depot, our technicians specialize in diagnostics and repairs for all major pool heater brands. We can pinpoint the problem, recommend the right replacement parts, or help you upgrade to a newer, more efficient system.

Pro Tip: Always keep your heater’s brand, model number, and serial number handy — it helps us identify compatible parts faster.

Most of the time, a pool heater that won’t turn on isn’t broken — it’s just being cautious. The system is designed to protect itself when something seems off, whether it’s low flow, poor ventilation, or power disruption.

By learning to troubleshoot the basics, you can save time, avoid unnecessary service calls, and get your pool back to the perfect temperature sooner.

And if you need help, Pool Supply Depot is your local expert in pool heater troubleshooting, replacement parts, and repairs across Nevada. We’ll make sure your system runs safely, efficiently, and reliably — so you can focus on enjoying your pool, not fixing it.