I don't know how to restart my old bosch water wizard 10p, pilot light has gone out.

Do you live in a climate where the hot water line could have frozen? If your heater did freeze up, that could be very bad. This is because water actually expands when it freezes and can do a lot of damage to pipes and to the water heater itself. My other thought is possibly a clogged in line water filter. But typically a clogged water filter would make it run with reduced pressure rather than a complete shutdown all water flow.

http://waterheatertimer.org/pdf/Bosch_10P-water-wizard.pdf

Gene

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Open following link for Bosch troubleshooting resources:
http://waterheatertimer.org/Troubleshoot-Bosch-Tankless-water-heater.html

Typical Bosch 10P manual shows temperature control illustration on Pg4, and includes low water temperatures on troubleshoot on Pg6
http://waterheatertimer.org/pdf/Bosch_10P-installation.pdf
Water flow rate too high, low gas pressure, faulty thermostat.

Two other things might be causing problem
Crossover:
http://waterheatertimer.org/Crossover.html
Lime build-up
http://waterheatertimer.org/pdf/Rheem-De-lime-tankless.pdf

What leads you to suspect that pilot blew out instead of another problem?
Fact that pilot will not relight, indicates other factors at play.

Open following link for Bosch troubleshooting resources including manual, and Bosch contact info:
http://waterheatertimer.org/Troubleshoot-Bosch-Tankless-water-heater.html

Best place to start is your manual.
http://waterheatertimer.org/pdf/Bosch_10P-installation.pdf

1) Manual recommends 'cleaning by authorized person, never less than once a year.'
Tankless water heaters, and most newer tank-type gas water heaters, are highly technical and finicky devices that require continual maintenance, with tankless requiring 'yearly' maintenance while tank-type require 'periodic' maintenance.
2) Troubleshoot in manual says 'no gas supply' or 'blocked pilot' replace pilot injector

Upvote the help.
And take advantage of fixya expert assistance live.
For a price, expert works with you while you work on water heater or any do-it-yourself project.
Fixya is always less expensive than a service call.

The manuals don't mention a battery.
Open following link for Bosch contact information and troubleshoot resources.
http://waterheatertimer.org/Troubleshoot-Bosch-Tankless-water-heater.html

Bosch gas 10p.
Word search of manual does not show battery.
Save the manual for future problems.
http://waterheatertimer.org/pdf/Bosch_10P-installation.pdf
http://waterheatertimer.org/pdf/Bosch_10P-water-wizard.pdf

Bosch electric under-counter P10-P15 resources:
http://www.boschhotwater.com/HelpfulResources/TechnicalSupport/AristonModels/P10P15Models/Troubleshoot/tabid/653/Default.aspx

Bosch P10 manual does not show battery during word search
http://waterheatertimer.org/pdf/Bosch-P10_P15_English.pdf

Open following link for Bosch tankless troubleshooting resources, including Bosch contact information, typical manuals, error codes, tech support, parts, fuel-saver calculator, service bulletins, water heater forum, fixya links, disclaimers, and links for finding service technician.
http://waterheatertimer.org/Troubleshoot-Bosch-Tankless-water-heater.html

Before calling service technician, read manual for fault finding and possible solutions.
Read manual cover to cover, make sure tankless receives yearly maintenance as outline in manual.
http://waterheatertimer.org/pdf/Bosch_water-wizard.pdf
http://waterheatertimer.org/pdf/Bosch_13P_16P_In.pdf

Following links talk about keeping pilot lit, and describe location somewhat. Bosch water wizard has standing pilot light.
http://www.fixya.com/support/t2961646-water_wizard_10p_pilot_light_keeps_going
http://www.fixya.com/support/t2960079-bosh_water_wizard_10p_pilot_light_keeps
http://www.fixya.com/support/t6182021-bosch_10p_tankless_hot_water

1) The manual does not show diagrams you asked for.

2) Website that sells Bosch parts does not show parts for water wizard, nor does Bosch site for parts: Instruction manual says: replace pilot injector
http://www.boschhotwater.com/HelpfulResources/PurchaseParts/tabid/837/Default.aspx
http://www.houseneeds.com/shop/heatingproducts/waterheating/parts/bosch2400espartsbuy.asp#

3) Searching "pilot injector for Bosch Water wizard" turns up fixya questions which is generally bad news for do-it-yourselfer because it means information sources are through service technician.

4) As a general rule, tankless are not do-it-yourself repairs or installation because they are affected by so many internal and external factors, including air quality, air flow, venting, other gas appliances, gas pressure, gas supply, water pressure, water flow, plumbing problems, water quality, plus internal parts and including any combination of things listed above..
Replacement parts each come will disclaimer.

Add a comment with your experience so others with same-similar problem can benefit.
Send some photos so the internet can see the problem.
http://www.fixya.com/support/r6568559-post_photograph_fixya_questions_answers

Also take advantage of fixya expert assistance live.
For a price, expert works with you while you work on water heater or any do-it-yourself project.
Fixya is always less expensive than a service call.

Check to make sure the flame of the pilot is hitting the thermocoupling. If not then you can use compressed air to clean the pilot port and relight and check again. If the flame is hitting the thermocouple, then it may need to be replaced.

If the thermocoupler is defective the gas to everything is shut off. The coupler is the bulb that sits ib the pilot flame If it doesn't heat up it will sense no pilot and shut the gas off. They don't cost much and are easy to change. Good Luck, Ned

Very possible the thermocoupler is no good. The thermo coupler is that bulb that is in the pilot flame. It controls the main valve It's not expensive and fairly easy to change out.. Make sure you get no dirt in the cspillary tube hole.brass screw end. The bulb must be just in the flame tip when adjusting. Good Luck, Ned-

You need a new thermocouple. Its the little stick like thing that the flame heats up to tell gas valve to open.