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Thread: Hayward H100ID Gas Valve and Control Module Troubleshooting

  1. Back To Top    #1

    Join Date
    Jul 2015
    Minneapolis, MN

    Hayward H100ID Gas Valve and Control Module Troubleshooting

    Hi - PoolGuyNJ helped on a similar thread, seems to know these things inside and out.

    I have studied how these heaters work (all of the safety interlocks and switches), but I need a better level of understanding on how to determine if I have a bad gas valve or a bad control module.

    Unit was purchased used, because the exchanges internal flow diverter spring was loose and rattling (common on these). I resolved that, cleaned everything, learned the schematic and operation very well, had a licensed plumber run the gas line, and we've been enjoying it for days. A few days ago, it showed the behavior identical to another thread. "Hayward H100ID Das Heater - Cycles Once, Then No Heat" but now I am not getting ignition even when the control board sees 120v and the igniter is firing.

    All of the interlocks/limit switches, etc ultimately do only 2 things:
    #1 if at least flow conditions/thermostat/panel interlock met, supply 120v to the fan.. and
    #2 if all conditions met, supply 120v to the control board until the thermostat opens.
    Control board has only 5 connections; ground, neutral, switched line (as in #2 above) and purple out to the gas valve, and the igniter cable. Gas valve rated at 120v, purple line should be supplying 120v or close.

    Here is what I am seeing:
    Plug unit in. Gas line valve is open, pump running, thermostat on high, fan engages, after a few seconds, you can hear the igniter sparking. NO THUNK from a gas valve opening. Igniter continues to fire several seconds and stops. Fan keeps running, no heat felt at exhaust. After awhile, the igniter fires again. Control board is continually supplied with 120v... I'll repeat, I am NOT losing 120v to the control board.

    I am guessing the control board is not supplying 120v to the gas valve (control board bad) or gas valve bad. I have NOT been able to measure anything over a volt or two on the purple line, so my next step is to apply 120v to the gas valve. Don't worry, I'll shut off the gas at the heater and even in the basement at the home's manifold. I know what I'm doing.

    I do wish I understood the gas valvue unit itself better. It gets neutral, the purple line already mentione, but then has some type of jumper block. Can anyone describe in lower detail how the gas valve ITSELF isworking? Example, If I knew that the gas valve is "dumb" i.e., it either gets 120v or it doesn't; it either opens or it doesn't, then if I have to troubleshoot the control board, I know that it is "only" switching 120v on or off. What I cannot figure out, is whether there is any feedback signal back to the control board (not unless it uses that same purple line/feedback is incorrect voltage drop).

    Does anyone know these things well enough to speculate?
    Davids in Mpls - 18' above ground Intex Ultraframe
    Hayward H100ID style 100k BTU hearter

  2. Back To Top    #2

    In the Industry

    ps0303's Avatar
    Join Date
    Jul 2011

    Re: Hayward H100ID Gas Valve and Control Module Troubleshooting

    Yes the gas valve is dumb. It either get voltage to open, or it doesn't. As simple as that. You should be able to put your meter on the wires to the gas valve or at the control module to see if it is supplying the correct voltage to open the gas valve.
    Paul A word of caution: When working with gas and electrical you might want to consider a licensed contractor. Consider the value of your life and others around you. If you would like to provide a review of the help I provided, please use the following link to leave a review. gastek - Google Search,

  3. Back To Top    #3

    TFP Guide

    Join Date
    Jun 2012
    western NY

    Re: Hayward H100ID Gas Valve and Control Module Troubleshooting

    if the control board inside the unit looks like this one...

    Then check the pins coming thru the board for bad solder connections. The pins can be seen in this image...

    I have had to re-solder several of these over the years. Sometimes it takes a magnifying lens to see the cracks.
    Unknown make 18' above ground (bought used in 1999) Sparco sand filter. Hayward 100,000 BTu heater. 2 speed pump

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