Bosch Tankless GWH 715 Powers on but does not ignite. Reset does not do anything. Diagnostics not working i.e., water flow 00 but water flowing. May be faulty control unit but how do I confirm?

Check for obstruction in your watervalve. It has a flow meter, that needs to spin freely. Remove the watervalve and blow through it, you should hear it spin.
Also make sure you dont have an error code showing. Hold down your reset button for 5 seconds to reset an error code and get back to your set temp.

Is this a water heater? Bosch site might have manual. And service bulletins, but I have not heard of that model.
http://www.bosch-climate.us/Bosch-Hot-Water/
Call local service technician who is qualified to work on tankless computer that heats water.
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Are you looking for sell sheet pdf, or install-care manual, or service manual.
Search: GWH 715 ES manual .pdf
Adding .pdf to search parameter helps locate manuals.

Sell sheet with venting overview, technical and product specs:
http://www.globaltowne.com/manuals/sell_sheets/715-800SellSheetFINAL.pdf

Manual for ES high altitude, with installation, error codes and troubleshoot:
http://www.bosch-climate.us/files/201009031238250.GWH715ES_English_12.2008.pdf

I cannot find a service manual, or service bulletins:
http://www.bosch-climate.us/support-center/downloads/bosch-manuals/earlier-models.html

Before calling service technician, open following link for Bosch troubleshooting resources:
http://waterheatertimer.org/Troubleshoot-Bosch-Tankless-water-heater.html

Error codes are starting point for troubleshooting, and solutions vary by model and unit.
E4 is Backflow temperature sensor over 309 degrees F. Appliance will close burner and lock.
Check combustion air and backflow vent piping for blockage.
Check if secondary fan connections are disconnected.
Check venting specifications are met. Long vent lengths, venting with more than three elbows, blocked vent or combination venting may cause this failure.
Check sensor resistance

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http://www.bosch-climate.us/files/201008311810050.G3-11_A3-E3_Error_Code_Troubleshooting.pdf
Check out Link for help.
I have same problem.

either you main controller is bad, or the thermo couple is faulty


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suggest you complain to Borch sometimes lemons get through best of luck

The manual says to hold a match near the pilot while the ignitor is trying. It says that if the unit lights the pilot orifice may be dirty or clogged. Then the manual says to check the voltage on the igniter. It should be 1.3 volts DC minimum if it is not means the electronic control box is defective.

Let me know the status ...Kevin

The vent pipe you use is the correct size for the heater.Longer runs require bigger pipe.I also would check to see if the water is getting to hot.

Try this web site!
http://www.protankless.com/BoschProHome/GasProducts/BoschGWH425HN/tabid/506/Default.aspx
Copy & Paste to Google search engine.