Pool Heater Not Working? Here's What to Check First

When your swimming pool heater stops working, it can take all the enjoyment out of a cool evening dip. The good news is you might not have to panic right away. Here are the basics to check first.

1. Check the Power Supply

If your heater isn't turning on at all, start with the power.

• Make sure the heater is firmly plugged in or wired correctly

• Check if the circuit breaker for the pool heater has tripped. Reset it once. If it trips again, don't push it

• Find the main power switch for your heater unit and make sure it's turned on

• Some units have a reset switch near the control panel

If you see frayed wires or burnt smells, stop and call a professional.

2. Inspect the Thermostat

If the heater has power but won't start:

• Is the thermostat set higher than the current pool water temperature?

• If digital, are there any error messages?

• For manual dial models, turn it up and listen for a click

If the display gives a temperature reading that doesn't match the actual pool temp, the thermostat sensor may be off.

3. Examine Water Flow

Heaters won't run without proper water flow. Most have built-in safety systems that prevent firing up if water isn't flowing.

• Make sure the pool pump is running

• Clean the skimmer baskets and pump strainer basket

• Check the filter and consider backwashing

• Look for blockages in the water lines

If you hear the heater clicking on and off quickly, that points to circulation problems.

4. Look at the Heater Pilot and Burners (Gas Heaters)

• Check if the pilot light is lit (small blue flame)

• Make sure the gas valve is fully open

• If you smell gas strongly, don't attempt to light it. Back away and contact a licensed professional

• Check burners for rust, dirt, spider webs, or insects

• Clean surface debris with a soft wire brush if comfortable

5. Assess for Unusual Noises or Smells

• Clicking or popping could mean trapped air or scale buildup

• Loud humming or grinding could mean motor problems

• Strong gas smell — stop immediately, this is dangerous

• Burning odors like melted plastic — shut things down

Keep Your Pool Cozy

Catching heater issues early and checking the basics can go a long way in getting things sorted quickly. If you're unsure about anything — especially gas, electrical, or persistent issues — bring in a professional.