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Bosch gwh-425ef nat gas on demand heater

This unit is 4 years old and has run perfectly until recently. It ignites ok and the pilot stays lit and the burner will light all the way but when the unit goes to high fire it shuts down and tries to ignite again. This problem is sporadic - sometimes its fine for a couple of days and then it just decides to quit. Water is town water on a softener. Unit is clean throughout and water valve filter is clean. Exhaust has no obstructions and blower is working fine. Unit will sometimes shut down after a few minutes of use and then reignite after water is tuned off and then on again. The heat exchanger is clean and free from dust buildup.

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  • jackblack161 Feb 21, 2009

    I Have The Same Problem, What Was Your Final Fix

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Actually this sounds more like a bad ECO on the outgoing hotwater pipe. Disconnect it and ohm it out for about .5 ohms with a digital multimeter.

Posted on Jan 19, 2009

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Sound like pcb board is failing - control board

Posted on Nov 11, 2008

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