Question about Bosch PowerStar AE125 AE125 Whole House Electric Tankless Water Heater...

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No hot water!!!!!

I have had the A125 electric Powerstar for a little over a year now and it has NEVER put out really hot water. Just for a couple of seconds and that is rare!!!
We have it turned up all the way.
It has always clicked when the hot water is turned on also.
Now we have NO hot water at all.
The electrician is gone that installed it and we can't seem to get anyone that is interested in coming out to fix it!!!

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  • Anonymous Dec 10, 2008

    Have had the until 2 years. Had periodic problems last 6 months with water going hot then cold then hot erratically. Now no hot water at all. Certified plumber (by Bosch) came out and charged $139.00 to diagnose bad circuit board. Bosch says I have to buy a new board for $278.00. Then also have to pay plumber to change out the board $175.00. That is a total of $593 - about same price as a brand new unit!! Why doesn't the warranty cover this?? What a waste of money!

  • Anonymous Dec 16, 2008

    we had it for 6 months and worked perfectly till today... no more hot water, no light on...

  • christichesl Mar 21, 2009

    We are on our 3rd power star 125. The first cylinder clicks off and to get any hot water at all we have to go click the reset. This happens every time we use hot water. We spend more time in the garage clicking the reset than in the actual shower! In addition to that, we now have hot water for about 3 minutes, then cold for 3 minutes then luke warm.



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It is difficult to diagnose tankless water heaters remotely since there are so many variables to take into account. It might be helpful to check the troubleshooting information on your model at boschhotwater to see if a handy solution is available before calling out a service tech. There are PDF's viewable with more detailed information on troubleshooting (flow rate, power supply, inlet temp, graphics, etc.) and they have a tech support phone # which is very helpful.
If the light is on and you still don't have hot water, I would start by checking the thermal cutouts (breakers) on top of each heating module that could be tripped and need reset.

I can attempt to post walk-through if needed.

Posted on Dec 11, 2008


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Related Questions:

1 Answer

I have a Bosch Powerstar Ae115 and the left cutout keeps tripping. It has worked great for 5 years. When i reset it, the water gets warm again(never hot as it was before). What could be causing it to trip?

Water leaking into elements. Bad PC board. Undersized breakers. Undersized main panel.
Bosch Powerstar is a computer that happens to heat water.
If your 5-year-old laptop computer was malfunctioning, you would not be surprised.
But for some reason (false marketing by manufacturers?), folks believe a tankless computer is going to last 20 years.
Moreover folks also believe tankless will provide endless hot water while saving money.
The whole idea of tankless saving money is a load of sales-BS that defies physics and common sense.
There are no service manuals... except bosch website has troubleshoot section in product manual.
Call a bosch-qualified service tech.
Go to Lowes and buy ordinary tank heater, and fix your heater today for only $250.
Tank-type electric water heater can be easily repaired and maintained by homeowner to last forever... that is a fact


Jan 12, 2014 | Water Heaters

1 Answer

We need to replace the 6 way terminal on our Powerstar A125 tankless hot water heater due to a loose wire that got hot and melted the terminal at the end. How do you do this. We have the part to rep

What happened to the screws from the old terminal strip?
If it is a different size you need to drill new small holes in the box (not the tank or pipes) and attach it with self tapping screws. Make sure each wire of the unit matches the same wire being connected as the original connections.

Jan 27, 2012 | Bosch PowerStar AE125 AE125 Whole House...

1 Answer

Electric bill doubled last month, and we've had the Powerstar AE125 tankless electric for over a year. There are no leaky faucets.

There are a lot of other things that eat electricity. Like space heater and using ovens for heat. Heat pump.Central heat fan running all the time. House lights left on. Outside flood lights. Clothes washer using HOT water. Look around real good. It all adds up. Also the power co. may be charging more for "fuel" costs surcharges. Here in GA I'm paying a bit more now to pay for a nuclear power plant.

Dec 26, 2011 | Bosch PowerStar AE125 AE125 Whole House...

1 Answer

My water heater will not put out hot water. I have well water. My unit is 3 years old. The water would come out hot and cold and the started to come out warm, now its not heating at all. Please help.

Might be the flow sensor, these Bosch units have a lot of problems. Just to be sure, you do have electricity going to it and have not tripped a breaker? The specs. also say the inlet water should be 60 degrees at least. take care.

Feb 23, 2011 | Bosch AE125 PowerStar 4 GPM Indoor...

1 Answer

Heater is ae125 is about 2.5 years old no problem until now turned on water and but no hot water light or anything checked breakers,checked cutouts,plenty of flow,still no hot water

Hey did you ever get this fixed mine is almost the exact same thing we've been using ours for about 3 years and today nothing. Thanks for your help.

Dec 07, 2010 | Bosch PowerStar AE125 AE125 Whole House...

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I have had a PowerStar A125 for about a year and now the water is hot in the beginning and goes cold and then hot again. I have observed the light when the shower is on it cycles on and off. My wife wants...

If on a well, you can install a regulating valve in the line to help with this problem. You may have to play with the valve a little to find the right pressure to avoid those highs and lows. I installed a Bosch A125 and had this problem from the start. A little research un-earthed the regulating valve (I think around $25 at Lowe's or Home Depot) and we have had even hot water ever since.

Jun 15, 2009 | Bosch PowerStar AE125 AE125 Whole House...

2 Answers

Water doesn't stay hot PowerStar AE3.4

Are you using a single lever faucet? The install guide does indicate that you may need to reduce the input from the cold water side to ensure that water stays at a consistent temperature (see page 7 of the installation and service manual). Also, remember, this is a SMALL hot water heater. So if you're running for any length of time at full output, it may not keep up with you (see page 8 of the service an installation manual). I found the manual online at

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