Pool Heater Won’t Turn On? Here’s What To Do

Pool Heater Won’t Turn On? Here’s What To Do

Pool heater won’t turn on?

Try these troubleshooting steps to fix the problem


You know what’s great? When you crave a refreshing swim and have a pool heater to keep the water warm and comfortable

You know what isn’t so great? When the pool heater won’t turn on

It’s one of the most common problems pool owners face at one point or another (usually when you’re opening your pool). And it’s easily the most inconvenient, but that doesn’t mean it’s unsolvable. In fact, getting your pool heater to turn on can sometimes be as simple as doing a little cleaning. In other cases, it can involve more in-depth troubleshooting.

Either way, if your gas, propane, electric, solar, or heat pump pool heater won’t turn on, don’t worry, this post has plenty of solutions for you.


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What to do when your pool heater won’t turn on


Check the filter

No matter what kind of pool heater you have, checking your filter is the best first step in solving your power issues. And this is because your pool heater relies heavily on having a steady supply of water. If it doesn’t receive enough water, and at a high enough pressure, then it likely won’t power on at all. And if it does, it’ll probably shut off right after.

So here’s what you can do to make sure your heater receives enough water:

  • Keep your filter, and filter media clean
  • Empty out your skimmer and pump baskets weekly
  • Run your pump at least 8 hours

By keeping your pool system free from blockage, water can freely move through the pipes at a stable pressure. This is exactly what a pool heater needs to run.

Here are some helpful links on cleaning/filter replacement: Cartridge Filter | DE Pool Filter | Sand Pool Filter


Check the pool pump

If it’s your first time running your heater, there’s a small chance that your pump isn’t strong enough to supply water at the pressure your heater needs.

Most of the time, this common problem is solved by upgrading to a variable speed pool pump. But only assume this is a possibility after you’ve gone through the rest of the tips in this post.

Related: Why You Should Upgrade To a Variable Speed Pool Pump


Double check the plumbing valves

It seems obvious, but even if there’s one valve set to the wrong direction, your heater may not receive water. And if that happens, then it definitely won’t turn on. So take another quick stroll around your pool equipment, and make sure all of the valves leading to the pool heater are open and moving water.



My HEAT PUMP pool heater won’t turn on | What to do

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Possible Cause: Damaged or weak electrical connection

Solution: If your pool heat pump isn’t receiving the power it needs from the breaker, then it won’t power on at all. But if the heat pump was previously working and no longer turns on, a damaged electrical connection could be the problem.

  • Check that the heat pump is receiving adequate power (usually 24 volts depending on size)
  • Inspect the wiring for any tears or loose connections
  • Inspect the wiring terminals for corrosion


Possible Cause: Low water flow

Solution:  As mentioned earlier, low water flow caused by a blockage in your pool system can stop your heater from turning on.

  • Clean your filter
  • Empty the baskets
  • Make sure the pump is sending enough water


Possible Cause: Defective pressure sensor

A defective pressure sensor prevent your pump from detecting water, which usually results in a shutdown


  • Have a pool heater repair technician troubleshoot the part to see if it needs replacement
    (Note: Quickly and effectively replacing faulty parts is the most cost-effective way to extend your pool heat pump’s lifespan)


Possible Cause: Dirty heat exchanger

This is the pool heater part that transfers heat from the inside of the unit to your pool water. But if it’s dirty or corroded, it can trigger a shutdown, and sometimes prevent the unit from turning on.


  • Have a professional heater repair tech troubleshoot the part to see if it needs replacement

Related: When To Service Your Pool Heat Pump


Doing some pool heat pump troubleshooting?

[Check out these pool heater repair tips and troubleshooting hacks]



My GAS pool heater won’t turn on | What to do

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Possible Cause: Gas valve

Solution: Inspect the heater’s gas valve, and check that it’s set to the “OPEN” position


Possible Cause: Gas supply valve

Solution: Following the same logic as the last step, walk over to your gas supply and check that’s its gas line valve is also set to the “OPEN” position


Possible Cause: Pilot light isn’t lit

Solution: [Check here]


***The next 3 tips involves bypass testing, which requires opening up the heater. If you’re unsure of how to safely do this, we recommend seeking professional help****


Possible cause: Heater  switch


  • Make sure the switch is set to “ON:
  • Bypass the switch with a jumper wire by making connection with both terminals
    • If the heater turns on, the heater switch needs replacement
    • If it doesn’t, try the next tip


Possible Cause: The thermostat


  • Set the heater’s thermostat to a higher temperature than the pool water
  • Use a multimeter to check if the thermostat is receiving power
  • Use a jumper wire to bypass test the thermostat


Possible cause: High limit switch

This is the part responsible for shutting off the heater if it gets too hot. On most units, the switch is located near the heater’s outlets.


  • Bypass the high limit switch, if the heater triggers, replace the switch
    • Your heater may have more than one high limit switch, test both to see which one is the problem


[Have other gas heater problems?]
How To Troubleshoot Your Gas Pool Heater



My ELECTRIC RESISTANCE pool heater won’t turn on | What to do

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Possible Cause: Damaged or weak electrical connection

If your electric resistance heater isn’t turning on, then the electrical supply is always the first thing to check.


  • Check to see if the breaker is sending proper voltage
  • Inspect the wiring for damage
  • Check the wire terminals for rust or corrosion


Possible cause: Thermostat

Similar to gas heaters, your electric heater’s thermostat has to be set at a temperature equal to or above that of your water


  • Set your thermostat to a higher temperature
  • If nothing happens, use jumper cables or a multimeter to troubleshoot the thermostat


Possible cause: Burnt out

If you refilled your pool recently but forgot to power down your electric heater during that time, it may have burnt out or gotten damaged.


  • Call a professional to thoroughly inspect the heater for damage and any replacements needed



My solar pool heater won’t turn on | What to do

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Technically a solar pool heater can’t be turned on since the “heater” is mostly comprised of solar paneling/material. However, it is still powered by your pump.


Possible cause: Lack of direct sunlight


  • Wait for the sun to come out (wish we were joking)
  • If it is sunny out, try moving the solar panels/fixture (f possible) to a spot with better sun exposure


Possible Cause: Weak pool pump

Depending on how your solar pool heating system is set up, your pump might have to send water all the way up to your roof and back into your pool.  In some cases, smaller or worn out pool pumps may not be able to handle the job


  • Check the PSI of your pool system (air pressure gauge on your filter) for proper pressure levels
  • If using a variable speed pump, turn up the speed
  • Upgrade to a stronger pump

[Curious about solar? Check out this post]


Closing thoughts

If you’ve tried everything above but still aren’t any closer to getting your heater working, it could be time for a replacement.  Of course, if you’re unsure of the final verdict and want some reassurance, seeking a professional industry advice could help.

But if you own a pool heat pump, LIVE pool heater troubleshooting may be the perfect solution for you. Especially if you’re into DIY pool heater repair

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