Hayward Pool Heater Problem

  • Last Post 04 January 2022
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Rick54 posted this 28 November 2021

I have a Hayward H350FDN natural gas pool heater, it's worked fine for about 4 years.  Now it won't ignite, and has no error codes.  During the start-up process, when the gas valve is normally triggered to open, the fan motor seems to stutter and slow.  I put a multimeter on the valve circuit and it registers 24 volts (the correct amount) for only a brief moment during the startup process (when the fan motor slows briefly), so I think that the valve is OK.  Right now I suspect that the low-voltage transformer may be defective, but am curious if anyone else has seen these symptoms before.  Thanks.

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InyoRob posted this 29 November 2021

We contacted Hayward and this was the response from their tech. 

This doesn't sound like a gas valve nor a transformer issue.  The gas valve gets 24vac on each ignition attempt (3 times) unless it lights successfully.  After 3 failed attempts it should register an "IF" code for ignition failure.  The blower does pause for each ignition attempt, but if the blower motor is struggling then there should be a reduced amount of air flow which would trigger either the vent pressure switch or the blower vacuum switch and then triggering either an "AC" error code or "AO" error code.

Rick54 posted this 29 November 2021

Rob, thanks so much for the response.  I should have mentioned that if I let the heater go through 3 ignition attempts, it will result in an "IF" failure code.  But, this is the only error code.  The fan seems to spin up fine at first, and plenty of air is coming out of the vents on the top when the fan is running.  The fan does not "struggle" except for the brief moment when the 24v signal is being sent to the gas valve.  It should also be noted that the 24v sent to the gas valve is so brief that I cannot imagine that there would ever be enough gas in the combustion chamber to have any sort of ignition or flame.  Never have seen an "AC" or "AO" error code.  The heater interior is remarkably clean given its age and I've pulled and reseated all of the various electrical connections on the 3 circuit boards.  This really has me stumped.

InyoRob posted this 29 November 2021

I'd suggest having a gas appliance technician put a manometer on the gas valve and test the incoming fuel static, dynamic, and manifold pressures against the rating sticker in the unit before further diagnostics.

Rick54 posted this 29 November 2021

Rob, sounds like a good plan, but I'll be surprised if there are any gas pressure issues since there are some other gas appliances on this same "trunk" which still work fine.  Thanks so much for the input and I'll let you know what I find.

Rick54 posted this 30 November 2021

Rob in rooting around and mulling over this problem, I noted that the Hayward Installation and Service Manual states the following on page 37:




If the first ignition attempt fails during a normal heating cycle the control will make two (2) additional ignition attempts:

1. The control de-energizes the gas valve after the 4-second ignition trial ends. 


The foregoing has me a little stumped since the 24 volt input to the gas valve (the "ignition trial") on my heater lasts only for a second or so, not the 4 seconds specified above.  Would this indicate that the integrated control board has some sort of failure which would necessitate its replacement?

InyoRob posted this 01 December 2021

It could be the board. However, I reached out to the Hayward tech one more time for his input. Posted below was his reply.  

The sequencing is (1) heat up the ignitor, (2) open gas valve, (3) check flame sensor.  All that happens in less than 4 seconds.  If the flame sensor does not report a strong efficient flame then the gas valve closes and tries again.  After the third unsuccessful ignition then the unit reports "IF".  If any of the attempts are temporarily successful then the unit will re-start the ignition process.  

I'm a bit reluctant to tell a non-professional how to examine, test, and service a gas appliance, but with the professionals that are not familiar with these units I generally suggest the following.  First, check each device (listed above) for defects and proper connections.  Next, if the ignitor heats up, the gas valve opens, and the flame sensor is clean, wired, and mounted properly (grounding to the cabinet), then it's time to check the dynamics.  The fuel gas supply, both static and dynamic, should be verified, then the manifold pressures checked - if incorrect then they need to be addressed.  The burner tubes, burner try, orifice jets, and manifold should be cleaned - dust, cobwebs, foreign matter will either block the gas-air pathway or burn off, which appears as a weak flame and is reported as such by the flame sensor to the control board thus stopping the ignition attempt.  

It is possible that the control board is compromised and causing the problem, but without any evidence of that directly, all these other factors could prevent successful ignition.  If the questioner is not a gas appliance tech then I'd suggest they contact one for both expediency and safety.

Rick54 posted this 01 December 2021

Ron, once again I very much appreciate your efforts here.  And to put you at ease somewhat . . . I'm retired, but I was a Master Electrician and also a licensed Airframe and Powerplant mechanic with the FAA, so there is nothing in this heater which is a mystery to me.  I really appreciate you reaching out to the Hayward folks on my behalf.

I'd already removed and checked the igniter operation during the run-up process and it definitely heats up, but, like the gas valve, the input voltage is too brief to make it hot enough for ignition.  I'll pull the fan and make sure that there is a clean pathway for the heater's airflow and also check that the flame sensor, vacuum switch, and vacuum hose are in good shape and working properly. 

I guess if all of the various components are functioning and wired properly, then perhaps the ignition control board is the final step.  I'll let you know what I figure out, thanks so much.

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InyoRob posted this 01 December 2021

No problem at all. Keep us posted on what you find.

Rick54 posted this 01 December 2021

Rob, here are this afternoon's findings. 

1.  Disconnected one of the blower vacuum switch leads, fan started up, but got the correct error code on the keypad, "AO." 

2.  Disconnected one of the leads on the water pressure switch and one of the leads on one of the temperature limit switches, got an "LO" error code, jumpered the two wires (red and violet going back to the Control Module) and everything returned to "normal" (such as that is now).

3.  Disconnected power to the heater and turned the gas valve switch to "Off," no error code on re-powering and attempting a startup.

4.  Pulled out the ignitor, hung it over the side of the unit on an insulating pad with the wires still connected.  Upon startup, a few seconds prior to the gas valve being signaled to open, the ignitor glowed bright red, so it seems to be working fine. 

5.  Disconnected one of the ignitor wires and initiated a startup, got an "IO" error code.

6.  Removed and inspected the flame sensor, it appeared to be in good shape, but there is nothing in the Hayward Manual indicating if and how it can be tested (such as the ohm reading for the ignitor).

7.   Pulled the fan off of the burner housing, cleaned out everything I could see, mostly fine dust.  The burner area appeared pretty clean and soot-free.

8.   Removed the upper access panels on the heater and cleaned and vacuumed all areas I could reach, but it was pretty clean as well.

9.  Tested the voltage at the terminals on the gas valve with the valve connected, and just across the valve wires with them not connected to the valve.  In every instance, the digital multimeter would read zero, then spike to 24v for a second or less, then drop back to zero.  Never got a wiff of any gas at any point since I've been trying to get this issue resolved, but I don't think that the gas valve is ever open long enough to release any detectable amounts of gas (if it even opens at all).

10. Double-checked that the other two gas appliances on the gas line feeding the heater were still working fine.

11.  Checked all of the various fuses on both circuit boards (and re-seated each of them), they all appear fine with the fuse elements intact.

So . . . I may be at the point where I need to replace the Control Module, but, thus far, I can't seem to find any other reason for the abbreviated 24 volt signal to the gas valve.  In looking over the gas valve, it seems to be a pretty standard off-the-shelf 24 volt actuated unit with a 90 degree manifold attached to one end.  I suspect that the valve is fine, it's just not being told to open properly.  The valve does not appear to be of a type that would shut itself down if an over or under-pressure situation was present in the gas line feeding the heater (but, I may be mistaken about this).

If you would be so kind as to run all of this by those smart guys at Hayward, perhaps they have some other suggestions for steps I can take.  Thanks again.

Rick54 posted this 02 December 2021

Rob, just as a process of elimination, I ordered a new flame sensor to see if that's the issue.

InyoRob posted this 02 December 2021

Since the gas valve is receiving 24vac three times during an ignition sequence then I would not suspect the control board is at issue, but the gas valve exhibiting no gas, preferably measured with a manometer, then it is possible that the gas valve is internally shorted or shorted to ground and doing no work - not delivering gas into the burner tubes.  

This would be evidence of a failed gas valve:  

Never got a wiff of any gas at any point since I've been trying to get this issue resolved, but I don't think that the gas valve is ever open long enough to release any detectable amounts of gas (if it even opens at all).

Rick54 posted this 02 December 2021

Rob, thanks once more.  I'll keep you abreast of any developments.

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Rick54 posted this 20 December 2021

Rob, I had to take a bit of a break on this issue since I was having my pool re-plastered.  Once the plastering was completed, I replaced the flame sensor (problem persisted) and then the gas valve (problem persisted after this as well).  During the gas valve replacement process I also re-inspected and cleaned all of the gas jets (I had tried this earlier).

So, I'm at the point where I think that the only option left is to replace the control board and I ordered a new one today.  I'll let you know what happens when I install it.  Thanks again.

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InyoRob posted this 20 December 2021

Thank you for the update, Rick. Sorry to hear the flame sensor and gas valve didn't fix the issue. Keep us posted.

Rick54 posted this 28 December 2021

Rob, got the new control board in today, it took about 5 minutes to install it, turned on the power and the gas, switched the heater on and it fired right up . . . Success!

But, I sure wish I hadn't replaced the gas valve, flame sensor, and ignitor in the search for the problem.

Your help was invaluable and I can't thank you enough for your help and acting as a go-between with the folks at Hayward.

Hope you had a great Christmas and that 2022 is a wonderful, and bountiful, new year for you.

Thanks so much!

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InyoRob posted this 04 January 2022

That's awesome, Rick. I really appreciate you coming back and giving us updates. I'm sure this thread will help a lot of pool owners in the future.