Question about Hayward H-series Electronic Gas Pool Heater H400

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My H series pool heater won't adjust the temp up, only down. Is the control bad?

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  • Hayward Master
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Bad display control board

Posted on Oct 01, 2017


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Posted on Jan 02, 2017

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are you sure the code isnt FO , which would indicate flame sensor failure.usually can be solved by removing and cleaning fl sensor with fine emory cloth.since htr is calling for heat ,pressure switch does not need adjusting

Posted on Jul 23, 2009

  • 366 Answers

SOURCE: Heater ignites in spa mode but not pool mode

Sounds like you may have a bad temperature sensor. Check for damaged wires or have a technician test the sensors. they should have a certain resistance property, if they are not within the set parameters the sensor will not allow the heater to fire. If there is a separate thermostat for the pool side, check that as well.

Posted on Sep 15, 2009

  • 990 Answers

SOURCE: I can't turn off the unit without shutting off the

You are probally having a problem with your pressure switch in the heater. This is located in the cabnet on the left side about half wau up just above the burner tray. It will have a ferrel nut on the back you can unscrew to get it off the copper tube it is attached to. Do this with the breaker off and once it is removed from the tube start the pump for a second and see if you have a freeflo of water from tube. If you do you need to ck the pre sw by replaceing the unit on the tube and removing one of the wires to it. If this solves the problem you probally need to replace the switch. If you don't get water flo through the tube you will need to follow the tube to where it hooks to the manifold and remove it there and clear the hole it goes into and the tube it self. This is a rare occurence on these heaters as they have plastic headers. My bet is you will find the pressure switch has gone bad. Good lucl I hope this has helped.

Posted on Dec 02, 2009

  • 640 Answers

SOURCE: hayward pool heater h series

It could be that your gas connection has a blockage that is preventing adequate fuel for from getting to the heater. If that is not the case, try consulting your owners manual for these pool heaters. There is an online copy at the link below.

Posted on Dec 07, 2010

  • 310 Answers

SOURCE: I have a haywood h

Allheaters run off of a thermostat just like the heat to your house. It will shut off once heated to the selected temperature. Turn up the temperature, and monitor it for a couple days.

Posted on Dec 29, 2010

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