Question about Bosch AquaStar 2400ES-NG

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BOSCH AQUASTAR 2400ES NATURAL GAS TANKLESS HOT WATER HEATER

ERROR CODES A3 & E3 COME UP ALMOST DAILY, SOMETIMES THE HOT WATER TURNS COLD AND SOMETIMES ALL WATER STOPS FLOWING FOR A SECOND AND RESUMES COLD ONLY, UNIT IS 3-4 MONTHS OLD AND PROBLEM JUST STARTED THIS WEEK, SOMETIMES HITTING RESET DOESN'T BUY ENOUGH TIME TO FINISH SHOWERING

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  • dghbi Dec 31, 2008

    thank you, but have already been there and didn't find anything re: my hot water issues

  • kea957 Jan 12, 2009

    We had the same issues start about 6 months after it worked without an issue. It happens daily for no specific reason.

  • Anonymous Mar 18, 2014

    my water heater pvs50 split the tank near the bottom.it is two years old natural gas presssure is correct,it warped the bottom of the tank enough to pull the hot and cold stubs in toward the power ventor

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There are two issues here: E3 is an unrecognized code that does not appear in the Technician manual.  A temporary fix is to open the control panel and reseat the card edge connectors.  However the problem will most likely return after a period of time.  You really need a new controller board.
For the jumpers some people have experienced slight disconnections due to vibration in the units. Recommend using electrical tape to ensure that the jumper connector remains tight.

Posted on Mar 07, 2009

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Ea error code has two solutions ist. there is water in the gasvalve. unscrew the 4 screws and take the cover carefully off. you find water in the unit. there is also a rubber washer held in with a spring. carefully pull on it and a lot of water will flow out. solved my problem. the other solution might be the 3 electrodes.in the chamber . unscrew and pull them out. with fine sandpaper clean all 3 elektrodes and it will solve this problem. this is part of the annual maitenance that these units require. good luck. r

Posted on Feb 19, 2009

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The A3 & E3 codes are for the back flow sensor on the heater. Could be disconnected or a bad sensor. Call bosch tech support and they will help you with this.

Posted on Jan 18, 2009

  • Tim Hamlin Jan 20, 2009

    The two codes you are getting are for a jumper that is installed on the heater. It was designed so that some day you could cascade two units together and get more heat and water flow. They have not designed that segment for your heater. First of all find the jumper in the wiring, top right hand corner of the tankless unit you will see some wiring. The jumper is roughly 6 inchs long with a black section installed on the green wiring. You will need a digital multimeter to ohm it out. By specs it should ohm out at 120 ohms. If it does not, they will send you a new one from Bosch. You will need to call them to get the part. 1-800-642-3111

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Q. FA - Gas leakage error, gas valve circuit not closing properly
A.

  1. Disconnect power supply cord and check wire connections on gas valve and the two connectors on the control board.
  2. Flow water out of a hot water tap above the minimum activation point of .8GPM. Measure voltage at the gas valve wire connector. The connector should measure 24VDC between the left pair of wires and 24VDC between the right pair of wires when the unit is operating. If voltage is not correct, contact Bosch Water Heating for further instruction.
  3. Gas valve may be defective, contact Bosch Water Heating for further instruction.
Q. EA - No flame ionization detected with water flow
A.
  1. Verify that all manual gas shut off valves are open.
  2. Verify gas type (See Fig. 2 in installation manual) corresponds with the type of gas supplied to the heater.
  3. Reset error code and open a water tap to cycle the heater in an effort to purge air from gas line (especially on new installations). Cycling hot water tap on and off multiple times may be necessary. If heater still faults with EA error code, have a licensed gas technician properly purge air out of the gas line leading to the water heater.
  4. Verify the three yellow wire connections to the set of electrodes (underside of the burner assembly) are secure.
  5. Verify gas pressure meets specifications outlined in chapter 3.8. See Bulletin TWH-G2-03.
  6. Verify venting meets specifications outlined in chapter 3.6 of the installation manual. Improper venting may cause premature failure of the flame sensor rod.
  7. Observe inside the viewing window of the heat exchanger when a hot water tap is opened. Sparking should be followed by a steady blue flame. If not, Call Bosch Water Heating with observations. Readings from above gas pressure test will be required.
Q. C1 - Fan rotation too low on startup
A.
  1. Disconnect power supply cord. Check wire connections on back side of fan and the two large wire connectors on the control unit. Removal of lower access panel on control unit is necessary to access connectors.
  2. Verify that supply voltage is 120VAC and is properly grounded.
  3. Verify that venting meets specifications outlined in chapter 3.6 of the installation manual. Long vent lengths, venting with more than three elbows, blocked vent or combination venting may cause this failure. Verify backdraft flapper inside flue gas collector is not stuck shut.
  4. Check gas pressure. See Bulletin TWH-G2-03. Low gas pressure may cause the fan to change its speed to meet desired temperature.
  5. Possible defective control unit. Call Bosch Water Heating for further instructions.

Posted on Mar 15, 2009

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This answer actually relates to EA, FA, C1 error codes on Bosch 2400E. Tech service dept is extremely unhelpful. This particular model is extremely sensitive to water shorting out electronics, either dripping from ceiling onto unit (I have old house), or my recent experience, very cold inlet water (january) causing lots of condensation on all inlet pipes to heat chamber (mostly lower half of unit). Short-term solution: take off cover and using blow dryer on high about 8" away, dry lower half of unit, all electronics wires and sweating copper pipes (takes maybe 5 minutes), then hit reset button. Longer range solution: install dehumidifier in area to remove moisture from air before it can condense on cold water pipes and cause error codes. If unit draws outside air, try to keep doors closed to heater area, but still warm, to dry the rooms air. Tech service seems unaware of this issue. First time I called them, 20min on hold, then some guy answered the phone and immediately hung up. They su__. But I like the heater, ....when working, which is almost always when not wet inside for various reasons.

Posted on Jan 15, 2009

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Here's a link to a service bulletin regarding the A3 error code. http://www.bosch-climate.us/files/201109161600040.G3-11_A3-E3_Error_Code_Troubleshooting.pdf For some reason though my jumper is not in the location Tim describe, nor where the bulletin shows, but rather it just barely sticks out of the control unit. Mine measures 120.5 Ohms so I am still not sure what the issue is.

Posted on Dec 08, 2012

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Great technical support on this product available in Vermont, USA http://www.boschhotwater.com/HelpfulResources/TechnicalSupport

at Control Energy Corporation - I used to work there!

Posted on Dec 31, 2008

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