Question about Bosch AquaStar Indoor Natural Gas Tankless Water Heater with Vent Hood #125

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Bosch AQ125BNG gas water heater

My water heater all of a sudden stopped working. It will only produce a luke warm water. When it comes on, the flame doesn't seem to be as big as it used to be. also, the thermostat doesn't seem to adust the water temperature at all. any ideas? thanks, Justin

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  • hema18 Feb 06, 2009

    My Bosch 125B tankless water broke yesterday. It's not giving hot water, instead cold water is coming. When I turn the tap for hot water, I don't see the gas supply to the water heater.



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First thing I would do is clean and rebuild the watervalve. The watervalve on this heater mandates everything. This watervalve has a maintenance schedule in the manual. She be rebuilt every 3 years. Also sounds like the diaphram in the watervalve may be damaged.

Posted on Jan 19, 2009

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Hi Jason, it sounds as though you have a gas supply problem with it, now that could be due to a gas valve problem on the heater or a low pressure problem at the gas meter, 1st instance you should seek a Corgi engineer who will diagnose the prob if its a supply problem then you should contact your gas supplier, who will probaly change the gas regulator.

If its the gas valve it could be sticking or a blocked burner injector. This can be tested by the engineer with a manometer gauge which measures gas pressure. if there is a flow prob the thermostat will not function properly.

Hope this helps


Posted on Dec 15, 2008


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