Question about Bosch AquaStar 125FXKIT-NG 125FX Natural Gas Tankless Water Heater w/ Hood

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My Bosch on demand water heater won't stay lit

The pilot lights the emission array momentarily then it seems to run out of gas supply, then the pilot tries again, lighting momentarily then again goes out, seeming to run out of gas supplied. I think it might be a sensor telling it not to supply gas, or maybe a regulator that may need to be turned up? I see a spot on what looks like a regulator (manifold?) that has a groove on the front of it that looks like it may be adjustable with a flat blade screwdriver.

Any suggestions?

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  • Ned C Cook
    Ned C Cook May 11, 2010

    usually it's the thermocoupler that control the gas. It's that small copper or silvwe tube goin from the valve into the cobustion chamber of the heater. Is this equiped w/ pilot light or electronic ignitor?

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DO NOT try to adjust gas pressure unless you have the appropriate tools and gauges to do it right. You don't want to burn your house down.

First make sure all of the gas valves are fully opened. If that checks out and the problems continue, call an HVAC technician or your gas supplier to have them evaluate the adequacy of the supply line as well as the gas pressure at your appliance. Go with whatever they say or ask you to do.

Posted on May 24, 2009

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