Hayward Pool Heater LO Code [Fix It In 2 Minutes]

It is not uncommon for Hayward pool heater owners to experience the LO error code in their pool heater. Hayward pool heater LO error codes can be difficult to figure out, even for professional pool repair contractors. In this post, we explain the LO code, its causes, and how to solve it. We’ll also explain the steps you should take to make sure that they don’t appear again.

If your Hayward pool heater is displaying the LO code, it means that the limit string is open and the heater will shut down and enter lockout mode. To fix the problem and close the limit string, you’ll need to wait 2 minutes for the automatic restart.

A malfunctioning temperature limit switch, water pressure switch, or vent pressure switch indicate a problem in the Hayward heater. To fix this problem, ensure you have a functional pump that is backed by sufficient water flow and pressurized properly. Replace components if your heater does not react to these changes. Also clean the filter.

There can be many reasons why your pool heater might trigger the LO code, but don’t worry – there are also plenty of solutions. We’ll go over some of them in the sections below.

Hayward Pool Heater LO Code – Troubleshoot And Diagnosis

Hayward Pool Heater LO Code

You should only hire a professional to do Hayward pool heater troubleshooting if you have no idea how to or don’t have the time to do it yourself. Hiring an expert is always the best way to keep your pool heater in top condition and avoid any major problems from happening.

The LO code can be caused by a variety of different factors, including:

Defective Water Pressure Switch: Operate the water pump, making sure there is enough flow and that all connections are secure. Clean any filters that may be present, and replace the water temperature switch if necessary.

Defective Temperature Limit Switch: Make sure there is enough flow and the connection is good. If necessary, replace the temperature limit switch.

Defective Vent Pressure Switch: Make sure there is enough flow and that everything is properly connected. If necessary, replace the vent pressure switch.

If you want to clear the LO code on your Hayward heater, you’ll need to take care of any issues with the limit switches and wiring. In addition, make sure the water pressure is set correctly for your installation (above or below water level).

Defective Water Pressure Switch

The water pressure switch, located on the outside of the water heater, turns off and on based on the level of water in the heater tank. If there is no water in the tank, it is switched off and vice versa when there is a sufficient level of water. This helps keep energy costs down and ensures that there will be enough steam available during peak hours.

The main function of a water pressure switch is to turn off your water heater when the circualtion pump stops moving.

Symptoms of a faulty water pressure switch in a Hayward heater may include the heater shutting off unexpectedly or failing to turn on. To diagnose and fix this issue, follow these steps:

  1. Check if the pump is running.
  2. If the pump is running, check whether water flow is adequate for the switch to work properly.
  3. If water flow seems good, check for any electrical connection or wiring faults.
  4. check the status of the water pressure switch contacts to see if they are working.
  5. Next, make sure that low pump pressure is not the issue by checking things like dirty filters or wrongly positioned valves.
  6. Then, take a look at the settings on the water pressure switch to see if they are correct.
  7. Finally, check if the water pressure switch itself is in working condition or if it is defective.

There are several reasons why your Hayward pool heater might display a LO code. Most often, this is due to an issue with the water pressure switch. These checks are specific to that component and should help you resolve the problem.

LO Code Fix

Possible remedies for each diagnostic test are as follows:

  1. If you’re getting the LO error code on your Hayward heater pump, it’s likely because the pump is turned off. Make sure to turn it ON.
  2. It is important to ensure that the water flow rate is above the minimum required amount.
    For the H150FD and H200FD, the minimum is 20 GPM. For the H250FD and H300FD, it’s 25 GPM. And for the H350FD and H400FD, it’s 30 GPM.
  3. It is important to ensure that the wire harness terminals are securely connected to the spade terminals on the Hayward heater water pressure switch. This will help ensure optimal performance of the heater and avoid any potential problems.
  4. If you’re troubleshooting a Hayward heater with an LO error code, one potential cause could be the water pressure switch. To test this, disconnect the wire leads from both the water pressure switch and the jumper leads, then operate the heater while measuring continuity across the water pressure switch. If it’s open, then replace the water pressure switch. If it’s closed, simply remove the jumper and reconnect the water pressure switch.
  5. If you’re having trouble with low pump pressure, a good place to start is by cleaning the Hayward heater filter. Make sure all of the valves are in the correct position for maximum pressure, and that should help resolve the issue.
  6. If the Hayward heater water pressure switch is not set up correctly, follow the manual’s instructions to adjust the settings.
  7. If your Hayward pool heater is displaying an error code LO, it may be due to a defective water pressure switch. In this case, simply replacing the switch should resolve the issue.

If you’re unsure if your pool heater is working as it should, we recommend getting in touch with a professional to test what’s wrong — they can fix whatever might be amiss and ensure your whole system is operating smoothly.

Defective Temperature Limit Switch

Your Hayward pool heater may display the LO code for a number of reasons, one of which is a defective temperature limit switch. This switch is designed to keep the pool heater’s temperature within safe limits and is also known as the furnace plenum thermostat. If it’s not working properly, the LO code (among other Hayward pool heater error codes) may be displayed.

1. It is important to check the temperature limit switch wiring on the Hayward heater to ensure it is functioning properly.

In order to keep your Hayward heater temperature limit switch functioning properly, it is important to securely fasten the wire harness terminals to the spade terminals. Additionally, double check that all other wiring and connection issues have been resolved.

2. Inspect the Hayward heater temperature limit switch to ensure that the contacts are in good working order.

In order to check the connections to the Haywards Heater temperature limit switch, you will need to remove the wire leads from both the jumper leads and the limit switch.

Once this is done, operate the heater and measure the continuity across the limit switches. If there is no continuity, this indicates that the LO code is caused by a defect in the temperature limit switch. However, if there is continuity, move on to the next step.

Unplug the temperature limit switch, then remove the jumper.

3. It is important to ensure that your Hayward heater has adequate water flow.

Make sure your Hayward heater has adequate water flow. For the H150FD and H200FD, that means 20 GPM. For the H250FD and H300FD, it’s 25 GPM.

4. Check to see if the Hayward heater temperature limit switch is functioning properly.

If the temperature limit switch on your Hayward heater is defective, you can replace it with a new one. Make sure to get the same type of switch to avoid any compatibility issues.

If your Hayward heater is having issues with the temperature limit switch, it’s best to enlist the help of a professional. These fixes may require someone with expertise to get the job done right. The same goes for when the high limit switch keeps tripping. Let a Hayward professional lend a hand so you can enjoy your pool worry-free.

Defective Vent Pressure Switch

There are a few different reasons why your Hayward pool heater might display the LO code. One possibility is a defective vent pressure switch.

The vent pressure switch is a safety switch that is mounted to the side of the Hayward heaters. This switch is a Normally Closed switch that will open if the pressure in the vent line is too high. This switch is used to shut off the heater if the pressure gets too high and will not allow the heater to turn back on until the pressure has been released.

If the pressure switch is not working properly, the exhaust fumes could potentially poison the indoor air.

To find the vent pressure switch on your Hayward pool heater, consult the manual. If you can’t find it, call a pool heating expert.

1. To troubleshoot your Hayward pool heater vent pressure switch, start by checking the wiring and connections to and from the switch. Inspect the wires for any damage or loose connections, and make sure they are all properly connected to the switch.

In order to ensure that your Hayward pool heater is functioning properly, please check that the wire harness terminals have been securely and correctly connected to the vent pressure switch spade terminals. If they are not, please connect them properly.

2. To check the status of your Hayward pool heater vent pressure contacts, make sure they are secure and in good condition. By doing this, you can determine if they need to be replaced or not.

To troubleshoot the Hayward pool heater, remove the pressure gauge wire leads from the jumpers and vent pressure switch. Turn on the heater and measure for continuity across the switch to determine if it’s closed or open. If it’s open, troubleshoot code LO by removing a different component of the vent circuit (switch, relay or thermocouple).

3. It is important to keep your Hayward pool heater flue clear of any blockages or restrictions.

To ensure your Hayward pool heater is operating safely and efficiently, it is important to check the manual for the appropriate vent sizing. Make sure the vents are not blocked or clogged in any way, as this could pose a safety hazard.

4. If you have a Hayward pool heater, you may need to check the vent pressure switch to see if it needs to be replaced. This can be done by testing the switch with a multimeter.

If your Hayward pool heater’s pressure switch is broken, you can easily replace it with a new one.

Final Thoughts

If you’ve tried the steps outlined in this post, and your Hayward pool heater is still throwing the unwelcome LO error code, it’s time to call a technician. If water flow has been restricted somehow, or you smell a rusted-out exhaust pipe when you fire up your heater, get someone to take a look at it — as soon as possible.

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