Help! Bosch just quits. No error code.

[cgl5150]

Hello, I have a Bosch GWH 715 ES tankless water heater. It has been in service for a year and has worked great. I have cleaned it twice (vinegar flush). Here's the problem: Its fires and starts to heat, runs until it reaches temp, then it shuts off and starts again the repeats this over and over. I don't receive an error code. I thought it may be the sensor on the out side (hot) of the unit, replaced it, no dice. Here's why I thought it might be that sensor: If I take it off the pipe, the unit runs continually until I shut the faucet. Clip the sensor back on the pipe and it it does the start/stop thing again. It has good pressure to it, the little witches hat filter is clean, I'm stumped!
Thanks for any help.

 

[Justin B. Williams]

im fairly new to the whole tankless trouble shooting .. but perhaps and bad overheat sensor or waterflow sensor??? the troubleshooting manual doesnt really give you alot of options.. ill ask one of the certified techs we have at work. have you checked the actual output temp at the unit ?

 

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[RANDELL]

Sounds like you're having the same Bosch luck I'm having. In my case the error code is SHBAB or "Shouldn't Have Bought a BOSCH"