You need to have the flow switch looked at. The low flow of the water to the lavs and the kitchen sink, they all have as small demand next to t bath or shower,
Tom
Tankless water heaters require yearly maintenance to check gas pressure, inspect and clean burner and combustion parts, inspect vent and vent drain, clean air filter, check water flow, de-lime the heat exchanger etc. This maintenance can stop ordinary problems from occurring, and can be done by the homeowner by reading Bosch service manuals for specific model number. The continual maintenance, and cost of repairs and parts, and cost of professional service are more expensive than expected $1-8 monthly energy savings from owning tankless.
Before calling service technician, open following link for Bosch troubleshooting resources. This is a handy page to have on file. Read your manual cover to cover several times to identify troubleshooting and yearly maintenance protocol. http://waterheatertimer.org/Troubleshoot-Bosch-Tankless-water-heaters.html
There is a long list of plumbing and minor/majot tankless problems that cause unit not to work. And as you correctly surmise, you might need a plumber first, and gas company second, and electrician next. http://waterheatertimer.org/pdf/No-Error-Code.pdf
Add a comment for more free help. 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.
The manual mentions 'switch' several times, but does not say on-off switch http://waterheatertimer.org/pdf/AQ1-425HN-manual.pdf linear spill switch reset button linear spillage sensing switch linear spillage switch gas pressure switch safety switches
I am not aquainted with the Bosch..... But it is a heater. I am going from past experience with gas furnaces and how the process works..... You said that you can get the pilot to stay on if you unhook the Main Gas Valve wire. Do you have 24 Volt power on that wire to Common? Does this have a Flame Sensor? Maybe it got damaged. Does it have a good ground from the burner to the ignition control module? Does that wire to the electro valve go into a plug that plugs into the ignition control.... Maybe that pin is not making contact to the board. Hope this helps If no one else answer right away repost Or call and see if you can get Tech support from Bosch..... I know how frustrating it is you buy something brand new and it doesn't work
Sounds like you're dealing with a pesky issue. It could be a technical glitch or just a setting hiccup. Have you tried resetting the timer or checking the settings? If that doesn't do the trick, it might be worth getting a professional to take a look.U can also check some info about alphamechanicals. They got my air conditioning installation in Orangevale, CA https://alphamechanicals.com/service-area/orangevale-hvac-service/ and as I know they has to know something about bosch devices
Losing pendant displays on cool to cold mornings with your Bosch Highflow 25 EC hot water heater could be caused by temperature-related issues affecting the display module. Cold temperatures can affect electronic components, causing them to malfunction. It's possible that there could be a loose connection, moisture buildup, or a fault in the display module itself. I'd recommend contacting Bosch customer support or a qualified technician to diagnose and fix the issue.
If your Bosch Highflow 21e hot water system is experiencing fluctuations in water temperature while showering, it could be caused by a few different factors. Here are some possible reasons for this issue:
Flow rate too high: The hot water system may not be able to keep up with the demand if the showerhead or tap is allowing too much water to flow through. This can cause the water temperature to drop suddenly. Try reducing the flow rate by turning down the tap or using a low-flow showerhead.
Water pressure fluctuations: If the water pressure in your home fluctuates, it can cause the hot water temperature to vary. This can be caused by various factors, such as other appliances using water at the same time, or changes in municipal water supply pressure. Installing a pressure regulator or a flow restrictor may help to stabilize water pressure.
Blocked or dirty water filter: A clogged or dirty water filter in the hot water system can restrict water flow, causing the water temperature to fluctuate. Check the filter and clean or replace it if necessary.
Malfunctioning thermostatic mixing valve: The thermostatic mixing valve (TMV) regulates the water temperature in the hot water system. If it's faulty or dirty, it can cause temperature fluctuations. A licensed plumber or technician can inspect the valve and replace it if necessary.
Faulty temperature sensor or control board: If the temperature sensor or control board in the hot water system is faulty, it may not be able to maintain a consistent water temperature. A technician can diagnose the issue and repair or replace the faulty component.
If you're unsure about how to diagnose or fix the issue with your hot water system, it's best to contact a licensed plumber or technician for assistance.
The Bosch JSRZ 5-T PG tankless gas water heater may not start automatically because of problems with the magnetic sensor valve, power supply, or control unit/thermostat. Possible troubleshooting steps are:
inspect the water inlet valve and replace if faulty
confirm that power to the unit is functioning
if the problem continues, seek professional repair service.
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.
your not making sense with you question --state it goes cold in middle of shower --but state it will stay hot or cold forever ----if its the latter continued hot till you shut off water that normal working if the unit shuts down during shower then you have a problem ----unit is set at one temp and runs at that temp and you use shower 1 handle / 2 valve what ever you own to adjust temp their are really only 4 reasons stops making hot water ----2 are usually well water supply --incoming water pressure /flow or to cold ----other are gas valve -or sensor so i would look into your shower handles since almost all have adjustments and anti scold safety