Question about Bosch Aquastar 125HX Temp Adjustment knob -8702000111

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Aquastar 125hx descaling

My water heater still warms the water slightly, but over time has become less and less warm. I was told it might need descaling. It is a tankless, propane water heater, with no standing pilot, and it ignites the gas pilot by a water wheel system.It used to heat very very well. How can I fix this problem?

Posted by Anonymous on


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SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

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Posted on Jan 02, 2017

  • 25 Answers

SOURCE: Bosch 125 Tankless Water Heater - Water not hot enough

Sounds more like the venturi in the watervalve of the tankless water heater is clogged. I would recommed rebuilding it and paying close attention to properly relubing the pushrod and cleaning the venturi.

Posted on Jan 19, 2009

  • 1 Answer

SOURCE: Tankless water heater pilot light will not stay on

It is most likely the water valve stuck open, telling the controls to heat water, that it thinks is flowing through it, but without actual flow it overheats. Depending on how comfortable you are with taking it apart yourself, you could open the valve to see if it just needs cleaned out, or if you have a ruptured diaphragm or some other cause.

Posted on Apr 22, 2009

  • 3433 Answers

SOURCE: The Pilot burner flame is large & yellow

the pilot is getting too much air and is an indicaiot of dirty or air/ fuel ratio imbalance. The pilot is wimpy and the thermocoupler has alot to do with the gas . Make sure your thermocoupler is on the tip of the flame. You may end up replacing it. because it is showing signs of eminnt failure. When it fals your curners won't fire up. Good luck.

Posted on Jun 09, 2009

  • 332 Answers

SOURCE: Looking for Outdoor Tankless propane water heaters

it will tell you right on the box if it for indoors or out doors either way they have to have a cover over them,,

Posted on Jun 09, 2009

  • 3433 Answers

SOURCE: Bosch Aquastar tankless water heater model

There should be a thermocoupler, it is that bulb that sits in the pilot flame. If it is not functioning properly the main gas valve will not open.. Hmmm, Is the main valve in the on position?

Posted on Oct 10, 2009

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My Bosch Water Heater keeps going off. I reset it and then A7 keeps coming up. We had a power outage for about 6 days. I do not have the manual. Do you know what it is and how to fix it? Thank...

Questions might be asking for a manual, and asks what error A7 means, and asks how to fix error problem, but model number of Bosch heater is not given.
Error codes are start-point for troubleshooting, and can include multiple causes.
So following answer provides general do-it-yourself resources, without saying that problem can be 100% diagnosed or fixed by homeowner.

1) Error code A7 is outlet temperature sensor fault.
Problems include: need for descaling, dirty inlet water filter, debris in faucet aerators, dirty wiring terminals, bad wiring harness, or bad temperature sensor.

2) Before calling service technician who can test failed parts and catch tankless up on yearly maintenance, open following links for Bosch resources including error codes, phone number, possible manual, and descaling instructions, and cleaning inlet filter:

3) Product manual: Question posted under model 125HX-LP
Open following link for possible manual:

4) Do it yourself service bullitens for 125HX-LP

5) Take a moment and rate answer:
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.

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Insufficient gas presure. Check gas presure exiting regulator exrternal of water heater. If presure is at 3.7-inches water column gas valve is defective.

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That particular tankless water heater has hydro-generated ignition. In order for it to function, it requires a certain water pressure and velocity. You can try turning on the hot water in two location in your house to see if that gets it started. If it does, try getting a higher flow shower head, or removing the limiters in your faucets.

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I need to convert this water heater to natural gas. Is there a kit available to do this?

No kits are available to convert his unit to NG. This is because the LP uses copper pipe and is within code, the NG uses black pipe and each unit is specifically designed, entirely, to use the gas associated with the unit.

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Looking for Outdoor Tankless propane water heaters

it will tell you right on the box if it for indoors or out doors either way they have to have a cover over them,,

Jun 09, 2009 | Bosch AquaStar Propane Tankless Water...

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