Question about Bosch PowerStar AE115 Tankless Water Heater...

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My AE115 has power going to it but no hot water

And the red lite is not on

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Make sure you have the water connections right. the inlet goes on the blue side. Also, your pressure must be a minimum of .8 psi. If not there will be no hot water and the neon will be off. other possible causes might be a crossover in your plumbing or a stuck flow transducer. Here is a link to a guide to explain how to check these items.

Posted on May 28, 2014


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I have a power star ae115 electric tankless water heater. It has performed flawlessly for approximately 5 years. A couple weeks ago it stopped producing HOT water but is still heating to Luke warm. The "...

5 years is about the lifespan for tankless.
You might have shorted element. That would explain cooler water and tripping reset.
Test element: power is off, disconnect wires from element; ohms = voltage squared divided by watt rating of element

Call service technician./ Call Bosch


If you need further help, I’m available over the phone at

Oct 14, 2014 | Water Heaters

1 Answer

The thermal cutout, on the left side, pops up when water stops flowing through the unit. The modules are Polymer. I can press the button, have tons of hot water as long as the water is flowing through...

The left canister probably has a grounded element in it, which will keep power going after the water is off. Either that or you have a bad triac on your control unit

Nov 03, 2013 | Bosch PowerStar AE115 Tankless Water...

1 Answer

I just replaced the circuit board, and the water gets warm, but not hot.

Problem might be crossover from failed single-handle faucet cartridge:

If you need further help, I’m available over the phone at

Oct 22, 2012 | Bosch PowerStar AE115 Tankless Water...

1 Answer

Powerstar AE115. Neon light off - Water not hot.

9:10 times the control board is bad. You are wise to suspect as much.

Mar 31, 2017 | Bosch PowerStar AE115 Tankless Water...

3 Answers

AE115 is 2 years old and stopped heating the water. The red light is very, very dim which tells me it's a power problem. I've had no problems at all until now. I replaced the two 40 fuses and that did not...

Here are some possibilities and checks.
  1. The high temperature thermal cut-out has tripped. This would general shut off the Neon Light as well as the elements. However, even though your light is on check anyways.
  2. The flow switch not activating, Shut off the power to unit. Open the unit and observe if the flow switch activates when the water is turned on. If not then you have a faulty flow switch.
  3. Water flow to high. Turn the hot water tap on at the sink, adjust the outlet service valve until the water comes out of the tap at the required temperature, increase flow for cooler, decrease for hotter.
  4. The power selector screw not turned all the way to high. Check and turn all the way to high
  5. Element not working. Turn of the electricity to unit and test the resistance of the element. Here are the proper resistance for the element (240 volts, 40amps has a resistance of 2x12ohms) if no resistance than one or both elements need replacement.
I hope this gives you some more areas to check. Thanks for using FIXYA, Good Luck to you and have a great weekend. Jeff

Apr 16, 2010 | Bosch PowerStar AE115 Tankless Water...

1 Answer

No Hot water...why Bosch tankless water heater, 2 years old

I dunno ... did you turn it on?

What kind of result do you expect from this kind of question???

Oct 09, 2009 | Bosch PowerStar AE115 Tankless Water...

1 Answer

The water will not get hot and the power light blinks like it is trying to work and sometimes it will work fine but it is getting worse at not working

make sure the flue pipe is clear out side, it needs to vent with no obstuctions, if it is clear it is time to call a tech, the circuit board may be having issue and might have to be replaced

Jun 06, 2009 | Bosch PowerStar AE115 Tankless Water...

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