Bosch 125FX Tankless WH

Hello everyone, I installed a Bosch 125FX natural gas water heater in my home in 2005. It has been working well up until a month ago. On one day, I noticed there was no hot water at the kitchen sink. I turned the faucet off and then back on again and everything was fine. A few weeks later, it happened to my wife when she turned the shower on. A few days later it happened again while I happened to be standing near by the heater. The heater goes through its normal "tick, tick, tick" but the burners never ignite. Water flow through the heater is normal and, clearly, it tried to start. I figure it is one of two things:
1. The igniter stopped working inspite of the ticking sounds 2. The gas valve isn't opening so there is no gas to ignite
This only happens one out of ten or twenty uses so the temporary fix is a quick off-then-on with the faucet. Being busy (and lazy) has kept me from investigating further. Do any of you have any experience with this model? Is there a common failure that causes this particular symptom?
Thanks, Pat
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On 8/26/2013 9:29 AM, Pat wrote:

Has anyone suggested cleaning the unit by disconnecting it from the water supply and pumping vinegar or other descaling solution through it? When the units hit the U.S. market some years back, most plumbers had no idea how to go about cleaning them. There are still a lot of plumbers who don't know how to clean them. Your problem could be due to lime scale buildup inside the unit. O_o
http://www.speedclean.com/products/tankless_water_heater_maintenance.aspx
https://tinyurl.com/mhwxroe
http://www.speedclean.com/bucketdescaler/

https://www.youtube.com/watch?v=VjU6caDOLWk

TDD
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WH:

Thanks for posting this. Unfortunately I can't help with your question, but you have helped me make a decision. I was considering replacing my 28 year old conventional 40 gal NG water heater with a tankless unit. My water heater has never had a problem until recently, but in the past month it occasionally will leak an once or two of water and I can't figure out where it is coming from. Some of the fittings are looking fairly corroded, so I thought I would just bite the bullet and replace.
I was considering a tankless, but it is twice the cost of a conventional 40 gal heater, so I decided to stick with a conventional unit rather than the more troublesome tankless.
Good luck with your problem.
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Maybe the TP valve weeps. In any case, 28 years is pretty ancient for a WH.
. Christopher A. Young Learn about Jesus www.lds.org .
On 8/26/2013 2:42 PM, CRNG wrote:

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