Fixing a Hayward Heater LO Code: Step-by-Step Troubleshooting

Stumbling upon a ‘LO’ code on your Hayward heater can be quite the head-scratcher. Don’t worry, you’re about to unravel the mystery behind this cryptic message. This code typically indicates a water temperature sensor error, but it can also be a sign of other underlying issues with your pool heater. In this article, you’ll learn the steps to diagnose and fix the problem, ensuring your pool remains the perfect escape for those chilly dips. Stay tuned as we dive into the nitty-gritty of troubleshooting your Hayward heater ‘LO’ code, keeping your pool time serene and uninterrupted.

Understanding the Hayward Heater ‘LO’ Code

When your Hayward heater flashes the ‘LO’ code, it’s alerting you to a water temperature sensor fault. This sensor is crucial as it monitors the pool water’s heat, ensuring it’s at a comfortable level for swimming. If the sensor isn’t working, the heater cannot calibrate the heat accurately, which might lead to an unheated pool or damage to the heater from overheating.

Hayward’s water temperature sensor error isn’t the only issue signalled by the ‘LO’ code. This troubleshoot message might also be indicating:

  • Incorrect water flow through the heater
  • A malfunctioning pressure switch
  • Blocked filter or pump issues causing low water pressure

Diving deeper, the cause of the ‘LO’ code could range from a simple obstruction in the filter that needs cleaning to more complex electrical problems within the heater’s circuitry. Regular maintenance checks usually prevent these issues by keeping your heater in optimal working condition.

If you encounter the ‘LO’ code, it’s essential to act swiftly. By addressing it early, you can sidestep further complications that could lead to costly repairs or replacement parts. Moreover, ensuring the heater operates correctly extends its lifespan, meaning more warm swims in your future.

Reasons Behind the ‘LO’ Code

When your Hayward heater flashes the ‘LO’ code, it’s alerting you to potential problems that need your immediate attention. Understanding the common causes helps you to troubleshoot effectively and get your heater back to its normal function swiftly.

Insufficient Water Flow

A primary reason for the ‘LO’ code is inadequate water flow through the heater. This can occur due to:

  • Obstructed pump baskets
  • Skimmer baskets filled with debris
  • A clogged filter

Regular cleaning of these components ensures unobstructed water flow, preventing the ‘LO’ code from appearing on your heater’s display.

Faulty Pressure Switch

The pressure switch plays a critical role in monitoring water flow and pressure. When it’s not working correctly, the ‘LO’ code may appear. This could be due to:

  • Scale build-up
  • A loose or damaged wire
  • An actual pressure issue

Replacing or repairing the pressure switch often resolves this issue.

Blocked Filters

Blocked filters restrict water flow, causing the heater to overheat or malfunction, which results in the ‘LO’ code. Cleaning or replacing filters regularly is a simple yet effective way to maintain optimal water flow and heater performance.

Temperature Sensor Failure

A defective water temperature sensor could also trigger the ‘LO’ code. Indicators include:

  • Erratic temperature readings
  • Heater turning on and off randomly

Replacing the sensor is typically the most straightforward solution to this problem.

By addressing these common causes, you’ll not only clear the ‘LO’ code but will also prolong the lifespan of your Hayward heater. Regular maintenance, including checking filters, sensors, and switches, will keep your heater functioning efficiently and reliably.

Steps to Diagnose the ‘LO’ Code

When the ‘LO’ code flashes on your Hayward heater, it’s vital you identify the problem quickly. With a systematic approach, you can troubleshoot effectively.

Check the Water Flow

Verify that your pool or spa water is circulating properly. Insufficient flow can trigger the ‘LO’ code.

  • Ensure the pump is operational
  • Clean out any debris from the strainer basket
  • Inspect filter pressure for irregularities

Assess the Pressure Switch

A malfunctioning pressure switch might be the culprit.

  • Turn off the heater and the pump
  • Locate the pressure switch for inspection
  • Test it with a multimeter to ensure it’s functioning

Evaluate the Filters

Clogged filters impede water flow, leading to the ‘LO’ code.

  • Remove and inspect the filters
  • Clean or replace them if they’re dirty or worn out

Inspect the Temperature Sensor

The sensor’s failure can directly result in the ‘LO’ code.

  • Find the sensor usually near the heater’s control panel
  • Check for any visible damage
  • Use a multimeter to check its resistance

Through these steps, you can identify the reasons behind the ‘LO’ code and take necessary actions to remedy the issue, ensuring your heater operates efficiently. Remember that regular maintenance is key in preventing such disruptions and prolonging the lifespan of your Hayward heater.

Solutions for Resolving the ‘LO’ Code

When your Hayward heater flashes the ‘LO’ code, rectifying the issue quickly is key to maintaining a warm and welcoming pool. Here’s your step-by-step guide to get your heater back up and running.

Check and Clean the Filters

Begin with your filters; a dirty filter can significantly hinder water flow. Ensure your filters are clean and free from debris. Simple rinsing or a chemical soak might be all that’s needed to restore proper flow and clear the code.

Verify Water Flow Rate

It’s crucial to verify the water flow rate, which should meet the heater’s minimum requirements. Poor flow can trigger the ‘LO’ code, and adjusting the valves or pumps may increase the flow to the necessary levels.

Inspect the Pressure Switch

A faulty pressure switch might inaccurately signal low water flow. You’ll need to inspect the pressure switch and ensure it’s properly connected and functioning. In some cases, replacing the pressure switch will resolve the issue.

Evaluate the Temperature Sensor

The temperature sensor’s accuracy is paramount. If it’s malfunctioning, it could display the ‘LO’ code. Test the sensor to see if it provides an accurate reading and replace it if necessary.

By systematically tackling each potential problem, you’ll often find the source behind your heater’s ‘LO’ code. Regular maintenance keeps these problems at bay and ensures uninterrupted pool enjoyment. Remember, it’s always best to consult your Hayward heater’s manual or a professional for specific guidance and troubleshooting.

Preventative Measures for Future ‘LO’ Code Occurrences

Regular maintenance of your Hayward heater can significantly reduce the chance of seeing the ‘LO’ code flash up again. By taking a few simple steps, you’ll keep your heater running smoothly and dodge unnecessary interruptions to your pool enjoyment. Here’s what you need to focus on:

  • Monthly Filter Cleaning: Dirt can accumulate in your filters, causing restricted water flow which, in turn, might trigger the ‘LO’ code. It’s therefore crucial to clean your filters monthly, or more often if your pool sees heavy use.
  • Adequate Water Flow: Ensure your pump is delivering the right flow rate to the heater. Check the manual for your model’s optimum flow rate and monitor regularly.
  • Regular Pressure Switch Tests: A faulty pressure switch could repeatedly signal the ‘LO’ code. Test this switch periodically to ensure that it’s in good working order.
  • Temperature Sensor Checks: Given that temperature discrepancies can cause the ‘LO’ code, yearly checks of the sensor can prevent future occurrences.
  • Annual Professional Servicing: Don’t overlook the benefit of a professional servicing your heater. They can catch issues that might not be obvious to you.
  • Proper Shut-Down Procedure: When shutting down your heater for extended periods, follow the correct procedure as stated in the manual to avoid system shocks that might cause errors.

By adhering to these preventative measures and incorporating them into your routine maintenance schedule, you’ll greatly decrease the odds of facing the ‘LO’ code, ensuring your Hayward heater remains a reliable source of warmth for your pool.


Armed with this guide, you’re now well-equipped to tackle the ‘LO’ code on your Hayward heater. Remember, regular maintenance is key to preventing issues and keeping your pool ready for a dip at any time. By following the preventative measures outlined, you’ll not only address the current problem but also safeguard against future occurrences. Keep your heater running smoothly and enjoy the comfort of your pool without interruption. Now, go ahead and put these tips into action – your Hayward heater will thank you for it.