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Thread: Hayward H300 Propane Milivolt not firing

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    Hayward H300 Propane Milivolt not firing

    Hello...I recently picked up a used Hayward H300 milivolt propane heater on CL...Before I became the proud owner, the heater had been bought and sold a couple times, with both of the previous owners never having actually hooked it up...so no one really 'knew' anything about it. I now have it all hooked up and of course, it isn't working.

    I can get the pilot to ignite and stay lit, as long as I continue to hold down the pilot gas knob on the gas valve, and while holding down the knob, there is a strong blue flame...but once I let it go, the flame either goes out completely, or is very faint and when I attempt to turn the gas knob to the 'on' position, nothing happens.

    I traced the troubleshooting flowchart from Hayward and it seems to indicate a bad gas valve? Can anyone substantiate this? The HAXGSV0003 MV gas valve seems pretty expensive and I would prefer to have an accurate diagnosis, before purchasing it...

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    cubbybeave08's Avatar
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    Re: Hayward H300 Propane Milivolt not firing

    Quote Originally Posted by cveino
    Hello...I recently picked up a used Hayward H300 milivolt propane heater on CL...Before I became the proud owner, the heater had been bought and sold a couple times, with both of the previous owners never having actually hooked it up...so no one really 'knew' anything about it. I now have it all hooked up and of course, it isn't working.

    I can get the pilot to ignite and stay lit, as long as I continue to hold down the pilot gas knob on the gas valve, and while holding down the knob, there is a strong blue flame...but once I let it go, the flame either goes out completely, or is very faint and when I attempt to turn the gas knob to the 'on' position, nothing happens.

    I traced the troubleshooting flowchart from Hayward and it seems to indicate a bad gas valve? Can anyone substantiate this? The HAXGSV0003 MV gas valve seems pretty expensive and I would prefer to have an accurate diagnosis, before purchasing it...
    Is there anything around the pilot light or igniter that looks like a sensor...many flamed pilot lights have a clean burning sensor...that if the sensor is dirty it will shut the gas flow off since it senses that the burners may be dirty thus sensing an unsafe situation. If you clean the sensor, usually with a piece of emory cloth...and then put it back in place it will usually start. If there is no sensor there than you are probably right the gas valve or the pilot light itself may need to be replaced...but I have this same issue with my gas burning fireplace...and all I have to do is clean that sensor. Give it a look.
    Beave
    Aqua Leader 24ft Round AG Wil-Bar Influence w/54 inch walls 13,500 gallons
    Swimline J-Blue Opal Liner, 1 4X20 Fafco Solar Bear Solar Heater
    Hayward 2 HP Swim Pro Voyager Pump Micro 150 with 4 way timer
    Swim Pro Voyager Filtration System with Hayward ABS Pearl wide mouth skimmer

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    Join Date
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    Re: Hayward H300 Propane Milivolt not firing

    That sensor is called the Pilot Generator. When heated, it needs to produce at least 250 mV-DC to keep the pilot lit and 400 mV to open the maIn gas feed when the thermostat calls for heat.

    By pulling the two wires off the pressure switch and check for the presence of the required voltage when the pilot is lit (your holding the knob down so it stays lit), you can tell if it's still good.

    Scott
    Owner of - PoolGuyNJ LLC
    Expert Pool and Spa Repairs, Renovations, and Augmentation. Helping people decide what is the right gear for meeting their needs. Expectations Set, Expectations Met, No Surprises.

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    cubbybeave08's Avatar
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    Re: Hayward H300 Propane Milivolt not firing

    Quote Originally Posted by PoolGuyNJ
    That sensor is called the Pilot Generator. When heated, it needs to produce at least 250 mV-DC to keep the pilot lit and 400 mV to open the maIn gas feed when the thermostat calls for heat.

    By pulling the two wires off the pressure switch and check for the presence of the required voltage when the pilot is lit (your holding the knob down so it stays lit), you can tell if it's still good.

    Scott

    Yeah what Scott said!!!! I knew it was something like that!!! That is why I have someone come out and service my fire place...I know just enough to be dangerous!

    Thanks for giving the correct answer and what to do!
    Beave
    Aqua Leader 24ft Round AG Wil-Bar Influence w/54 inch walls 13,500 gallons
    Swimline J-Blue Opal Liner, 1 4X20 Fafco Solar Bear Solar Heater
    Hayward 2 HP Swim Pro Voyager Pump Micro 150 with 4 way timer
    Swim Pro Voyager Filtration System with Hayward ABS Pearl wide mouth skimmer

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