Question about Bosch 1600H-NG Natural Gas AquaStar AquaStar Natural Gas Tankless Water Heater...

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How do i know if the control unit is bad on an aquastar 1600H

The unit just stopped producing hot water. the voltage on the hydro generator is 0.5 vac. how do i know if the control board is good or bad

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  • Peter Klepl
    Peter Klepl Nov 20, 2014

    i took the hydrogenerator off last night and found that the parts inside were broken. there was a rubber washer curled up, looks like it was coming apart for quite some time. possibly this was a defective hydrogenerator


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That voltage does not seem high enough. Supposed to be 1.6 VAC and I got 2.5 VAC. Do you have the water flow turned to the maximum? Is there something blocking water flow? The hydro voltage should be checked separetly from everything else, so if you can't get the VAC higher, my guess would be that's the problem.

Posted on Nov 19, 2014

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  • Peter Klepl
    Peter Klepl Nov 19, 2014

    so cleaning the hydro generator might raise the voltage?

  • zawy Nov 20, 2014

    If it's clogged, and if it can be cleaned, then maybe. I assume you have good and strong water flow when you turn on a hot water faucet. If you do, and if you disconnected one of the 2 wires of the hydrogenerator like you are supposed to (so that voltage is not drained off of it) and set your voltmeter to AC and it said 0.5, then something is wrong with the hydrogenerator.

  • Peter Klepl
    Peter Klepl Nov 20, 2014

    i took the hydrogenerator off last night and found that the parts inside were broken and had been deteriorating for quite some time. waiting for a new part to arrive

  • zawy Nov 20, 2014

    hmm, that's not cool.They should make water heaters to last a long time. I'm disappointed with Bosch. Since when did Germans starts doing shotty engineering (microswitch) or going cheapo on parts (hydrogenerator deteriorating)?

  • Peter Klepl
    Peter Klepl Nov 20, 2014

    i have no idea, but i wish that Rheem or one of the other popular brands would come up with a hydrogenerated tankless water heater as i would gladly upgrade to their equipment.

  • zawy Nov 20, 2014

    For 32 years I

  • zawy Nov 20, 2014

    For 32 years after reading about them in popular science I've wondered why tankless is not standard.


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Posted on Jan 02, 2017

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SOURCE: Bosch Aquastar 2400E LP Does Not Heat Water

Sounds like the water flow sensor and servo, may just need cleaning, get it checked out by a Bosch agent

Posted on Jan 17, 2010

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SOURCE: i have a 250SX aquastar bosch tankless hot water

The 250 MUST have the condensate line connected. EC comes from gas supply problems and CO2 levels not being adjusted. LP units require 3/4" smooth gas pipe or 1" corrugated pipe minimum size. The LP regulator needs to be turned up to about 13 inches of water column and with all the gas appliances on, measure no less than 11 inches of water column. The CO2 levels must be measured by a qualified gas technician with a calibrated (with in 6 months) CO2 analyzer.

Posted on Apr 11, 2010

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SOURCE: bosch aquastar Aq125-hx does not

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.

Posted on Jan 07, 2011

  • 159 Answers

SOURCE: Bosch 1600H-NG Natural Gas AquaStar

Possible flow sensor issue. Check to see if your water pressure fluctuates a lot or is fairly steady. These units are sensitive to the pressure. take care.

Posted on Mar 04, 2011

SOURCE: roblem with the Bosch 1600H-NG

Problem could be air supply, gas supply, venting, part failure or combination of listed things.

Best place to start is manual.

Typical 1600 manual shows troubleshoot starting page 19

Bosch has online tech support form:

BOSCH error codes:

Add a comment for more free help.
Also take advantage of fixya expert assistance live.
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Posted on Mar 05, 2011

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