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WCohn
WCohn, Journeyman Plumber
Category: Plumbing
Satisfied Customers: 511
Experience:  Journeyman Plumber/Estimator
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I have a Bosch ProTankless GWH 425 HN L with serial number

Customer Question

I have a Bosch ProTankless GWH 425 HN L with serial number beginning with 584. It will not light on it's own...red light flashes as water flows. However, it will light and burners will stay lit as long as I'm holding in the power button. Unit has just been flushed per manual and water inlet screen has been cleaned.
Submitted: 21 days ago.
Category: Plumbing
Expert:  WCohn replied 21 days ago.

Hello my name is ***** ***** I look forward to helping you!

I am a Bosch factory trained and certified repair technician

Expert:  WCohn replied 21 days ago.

It sounds like the water valve needs rebuilt.

Expert:  WCohn replied 21 days ago.

The water valve has a diaphragm in it that engages the gas valve allowing the unit to light. If it has a build up on it or a hole it will not flex enough to engage the gas valve.

Customer: replied 21 days ago.
Ok, that's what I was thinking, but not knowing enough about the unit, I couldn't figure out why it works by holding in the power button?
Expert:  WCohn replied 21 days ago.

You are overriding the water valve. You can only get parts at www.houseneeds.com.

I'd appreciate a five star rating for my advice

Good luck and thank you for using JustAnswer.

Expert:  WCohn replied 19 days ago.

Well, are you needing more help or are you satisfied with my answer?

Customer: replied 19 days ago.
Thanks for your help, but this has not solved the problem. I have cleaned and rebuilt the water valve with the kit from Houseneeds.com. I also replaced the diaphragm. Yet, I am still experiencing the same issue as first described. Do you have any other suggestions?
Expert:  WCohn replied 19 days ago.

I am sorry I am at a loss. Its so hard to diagnose remotely.

Customer: replied 19 days ago.
that's it then?
Expert:  WCohn replied 19 days ago.

I can opt out and allow some one else to answer you!

Customer: replied 19 days ago.
Ok, thanks!