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Pool Heater Not Working or Turning On? Here’s Why (+ Fixes)

Pool heaters are loaded with complicated parts. It’s important to quickly identify the problem since it can worsen other components. For example, loose wires can overheat the motherboard, which ruins everything connected to it. Your pool heater should be fixed as quickly as possible, especially if it won’t turn on or work properly.

If your pool heater isn’t working or turning on, these are the most common explanations:

  • Not enough water flow
  • Loose wire connections
  • Broken ignitor
  • Electrical issues
  • Not enough gas
  • Rusted parts

In this post, I’ll cover every possible reason your pool heater isn’t working and what you can do about it. I’ll also explain how you can prevent these issues from occurring to save time, money, and energy.

Not Enough Flow

If your heater doesn’t have enough water flowing through it, it’ll likely say ‘No Flow’ or ‘FLO,’ depending on the make and model. This common concern is often caused by clogged filters, pump-priming issues, air in the plumbing, etc. Anything that restricts the water flow will cause problems for the heater.

How to Fix

If your pump isn’t circulating water, try these suggestions:

  • Clean the filter to remove the debris limiting the flow.
  • Lubricate all O-rings and gaskets to prevent them from letting air into the system.
  • Tighten or replace the unions on every piece of equipment if you notice leaks.
  • Blow the plumbing lines to get rid of clogs.
  • Make sure you have the correct valve opened (it’s typically labeled as “heater”).

Not having enough water flowing through the equipment will cause error codes on almost every piece of equipment. You’ll likely notice debris in the pump basket or skimmer basket that needs to be emptied.

Loose Wires or Circuit Breakers

If your heater has loose connections, the motherboard won’t get enough power. Several wires and a circuit breaker supply electricity to the motherboard (also known as the control board), which powers everything else in the heater. These connections need to be solid and reliable to prevent random stoppages.

How to Fix

Follow this process to tighten the electrical connections:

  1. Turn off the power going to the heater.
  2. Tighten the wires going to the circuit breaker, heater, pump, and salt system (if you have one).
  3. Make sure the circuit breaker sits snugly in the breaker box.
  4. Turn on the power and test every wire with a multimeter.

If there are loose connections, you’ll likely notice power issues with the display board. The AstroAI Multimeter lets you test multiple power sources. The digital interface shows if you’re getting enough electricity. You can place the nodes against the circuit breakers or wires to know which part of the heater needs to be fixed or replaced.

AstroAI Multimeter Digital Multimeter

Broken Ignitor

The ignitor sparks the gas coming into the heater. If the ignitor is twisted, corroded, or damaged, it won’t be able to light the flame. The result is a minor gas leak or a heater that won’t turn on. The ignitor is one of the most problematic areas on a pool heater because rain and debris can clog and rust it.

How to Fix

To replace the ignitor, try this method:

  1. Turn off the circuit breaker and gas going to the heater.
  2. Open the front or top of the heater, depending on the make and model.
  3. Locate the ignitor and remove the retaining plate and screws (most ignitors have prongs on the end).
  4. Disconnect the ignitor from the wire clip, then reverse the process to install the new ignitor.
  5. Cover the heater, turn on the circuit breaker, and open the gas line.
  6. Wait for one to two minutes for the gas to fill the heater, then turn on the heater.
  7. Test the heater at a high temperature, then adjust it to the desired setting.

Follow this helpful video guide for more details:

Power Shortages

Power shortages can turn off the pump, heater, salt system, and other equipment. Make sure all of the equipment is receiving the same amount of electricity before jumping to conclusions. These power shortages can trip the circuit breaker, short the control board, and so on.

How to Fix

If there was a power shortage, turn everything off and on. If that doesn’t work, it’s time to figure out which part was fried. Take the previously mentioned multimeter and test every wire and circuit breaker connected to the heater.

Every part of the heater should have the same amount of electricity. Replace the parts that don’t have the proper power supply, starting with the circuit breaker.

A Lack of Gas

Gas heaters are the best heaters on the market. They’re efficient, quick-heating, and much more affordable than electric heaters. However, not having enough gas will cause your gas heater to fail. It might not turn on at all. Look for an error code that says ‘No Gas,’ ‘Gas,’ or something similar to know if there’s not enough gas going through the heater.

How to Fix

If you think there’s not enough gas getting to the heater, here are the two things you should do:

  1. Make sure the gas line is all the way open by turning the valve until it’s aligned with the gas pipe.
  2. Call a local pool expert to ensure there aren’t any leaks in the gas line or heater that could cause long-term hazards.

Rusted Components

Rust can ruin your pool heater by corroding the ignitor, motherboard, outer body, and more. The heat exchanger needs to be rust-free, which means there can’t be too much rainwater, pool water, and other moisture inside the heater. The good news is that you can remove the rust before it causes permanent damage.

How to Fix

If you notice rusted parts in the pool heater, try this:

  1. Crunch a ball of tinfoil as tight as possible, then dip it in dish soap and water.
  2. Scrub the rust until it’s gone.
  3. If the rust corrodes the component, it needs to be replaced as quickly as possible.


  • Jonah Ryan

    Jonah has worked for several years in the swimming pool industry installing and repairing equipment, treating pools with chemicals, and fixing damaged liners. He also has plumbing and electrical experience with air conditioning, ceiling fans, boilers, and more. When he's not writing for Temperature Master, he's usually writing for his own websites, and

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