Bosch Aquastar 125X Main Burner NG w/ Washer - Part 8708120298 Logo
L
Lawrence Koenig Posted on Oct 02, 2014
Answered by a Fixya Expert

Trustworthy Expert Solutions

At Fixya.com, our trusted experts are meticulously vetted and possess extensive experience in their respective fields. Backed by a community of knowledgeable professionals, our platform ensures that the solutions provided are thoroughly researched and validated.

View Our Top Experts

Main burner fire does not ignite despite good pilot fire, new thermocouple ??

Although the pilot light fires up briskly in response to a hot water tap opening and the ignitor continues to intermittently spark (for a few seconds after the pilot has fired up) the main burner does not fire up and after those few seconds of pilot light fire ... the pilot goes out, no main burner burns and my showers are brisk. I've changed the thermocouple (flame detector) and no change. any suggestions?

1 Answer

Gene Haynes

Level 3:

An expert who has achieved level 3 by getting 1000 points

Superstar:

An expert that got 20 achievements.

All-Star:

An expert that got 10 achievements.

MVP:

An expert that got 5 achievements.

  • Bosch Master 5,391 Answers
  • Posted on Oct 02, 2014
Gene Haynes
Bosch Master
Level 3:

An expert who has achieved level 3 by getting 1000 points

Superstar:

An expert that got 20 achievements.

All-Star:

An expert that got 10 achievements.

MVP:

An expert that got 5 achievements.

Joined: May 07, 2012
Answers
5391
Questions
0
Helped
2604521
Points
14124

5 Related Answers

co7196

Ned C Cook

  • 3433 Answers
  • Posted on May 06, 2009

SOURCE: no hot water, pilot light lights but no burner ignition

Thermo coupler may be defective. it controls the main gas valve by closing main if pilot is out. make sure thermo coupler bulb is positioned over and near tip of pilot flame, but not in the flame. Thermo couplers are inexpensive and easy to change out.

Ad
co7196

Ned C Cook

  • 3433 Answers
  • Posted on Jun 09, 2009

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.

Anonymous

  • 518 Answers
  • Posted on Jul 05, 2010

SOURCE: I have a Bosch AquaStar AQ-125-BNG tankless water

there is a small dia copper pipe which has a thermal coupling on it the end of it sits in the flame of the pilot light,
if it fails which it does after about 25-15 months,it shuts down the gas burner

Anonymous

  • 248 Answers
  • Posted on Oct 09, 2010

SOURCE: When I am taking a shower the pilot lite goes out,

sounds like thermalcouple/heat sensor

A

Anonymous

  • Posted on Apr 17, 2011

SOURCE: Replaced thermocouple on Bosch TF250.

Before calling service technician, open follow links for troubleshooting resources.
Bosch site does not show TF250, but shows 250SX and 250SXO.
Gas Products Technical Support: 800-642-3111
http://waterheatertimer.org/Troubleshoot-Bosch-Tankless-water-heater.html
http://www.boschhotwater.com/HelpfulResources/TechnicalSupport/BoschAquaStarModels/tabid/370/Default.aspx

At no time when visiting tankless website have I read suggestion that people fix tankless as a do-it-yourself project. In fact each site says repeatedly to call service technician for installation and repairs.
When reading service bulletins, the repair protocols are generally long and very sequential, even if a thermocouple seems straightforward there are many interrelated parts and sensors that must communicate exactly with each other.
Example: following pdf outlines operation sequence for non-standing pilot model
http://waterheatertimer.org/pdf/Tankless-gas-operation-overview.pdf

The dirty water also suggest that tankless has not gotten regular maintenance that is required for continued operation. Tankless are not install-it-and-run-flawless-for-years type of machine.
Read manual for specific maintenance required for your model. For example yearly flushing the heat exchanger with vinegar to avoid lime build-up is suggest most models. Tankless are succeptible to lime build-up.
All costs are energy. Maintenance alone can easily eat up the promised $1-8 monthly savings from tankless vrs tank-type water heater. One service call can wipe away years of expected savings, plus replacement part can sometimes cost as much as whole new tank-type water heater, installed.

Ad

Add Your Answer

×

Uploading: 0%

my-video-file.mp4

Complete. Click "Add" to insert your video. Add

×

Loading...
Loading...

Related Questions:

0helpful
1answer
0helpful
1answer

I can get the pilot light to stay on but main gas burner won't fire up

If the pilot is lighting and the thermo couple is in the fire and turned red and the pilot still does not stary on change the thermo couple. They are available in any home improvment store.
0helpful
1answer

We have a Bradford White Hydrojet Gas Water Heater. Model# MITW5016CX12. The blower comes on and stays on and the the igniter flame does not light. We are afraid that the blower will get too hot when we...

here's what Bradford White lists....
Burner Will Not Ignite
REASON REMEDY Excess primary air Adjust air shutter to reduce air supply -- if supplied No gas Check with utility Dirt in main burner orifice Clean orifice -- check for source of dirt and eliminate Dirt in gas lines Notify utility -- install dirt trap in gas line Venturi clogged Clean -- check for source of trouble and correct Pilot line clogged Clean -- check for source of trouble and correct Main burner line clogged Clean -- check for source of trouble and correct Defective thermocouple lead Replace with new thermocouple lead Defective thermostat Replace Defective magnetic valve Replace entire control Thermostat set too low Turn temperature knob to desired temperature Heater installed in confined space Provide ventilation by use of louvers in wall or door time for a service tech.
0helpful
1answer

Gas hot water heater will not automatically heat water, i have to manually start the burner to heat the water

Sounds like you have a bad thermostat. You can change the thermostat, but if the heater is more than 8 or 10 years old you might be better off to replace the entire heater. Thermostat replacement is easy:
1 turn off the gas 2 drain the heater 3 unscrew pilot, main burner, and thermocouple lines from bottom of thermostat. 4 unhook gas line from thermostat. 5 unscrew thermostat from heater tank. Use pipe sealer when you install new thermostat, and gas line fittings. burner and thermocouple lines seal on a taper seat and do not need sealer. after reassembly check for leaks with soapy water, not a match, light the pilot and turn up the temp. The heater may sweat quite a bit while it is heating up the first time, this is due to the cold water on the inside and the fire on the outside. some water may drip in the bottom of the heater and you might think you have a leak, but let it heat up completly, if the water is still dripping after the tank is hot then you need to find the leak.
0helpful
1answer

Gas water heater: burner doesn't fire, replaced gas control valve

Hello,Don't worry about the rust flakes as every burner collects then and is normal.The new control should click.Please check incoming gas pressure supply 3.5"WC natural gas / 9"WC for LP.Check it at the piolt tube with a pressure dial meter,I assume the water temp now is cold.Did you change the thermocouple also as this provides the power to run the control?
1helpful
1answer
0helpful
1answer

We dont think our cylinder is on we have just moved in and have no hot water

The question is? I'll assume you cylinder is the water heater, right?
On the heater (water) you will find or see the red controls and a sheet metal cover over a hole. Remove the cover and this is where you light the pilot light. Press down on the red dial and turn it to pilot. In that position you will be able to press the red button . Geyt a long match or bbq lighter, then, holding down the red button dow for a minute or so and place a match or lighter into yhe area where the lines go The flame will catch the gas and lite the pilot if yo simply move your glame around. When the flame catch on the pilot, continue holding the button down for sveral minutes until the buld the flame isheating gets hot. Then release the buton and turn the main dial to on. The main burner should fire up. If not, and the pilot goes out, repeat the process. The bulb in the pilot flame is a thermocoupler that shuts all gas off if it doesn't detect a pilot flame, so hold the button down longer. If the pilot goes out when you release the button, The thermocoupler is no good and needs replacing. Good Luck_Ned_
3helpful
2answers

My bosh water wizard 10P pilot light keeps going out.

Very possible the thermocoupler is no good. The thermo coupler is that bulb that is in the pilot flame. It controls the main valve It's not expensive and fairly easy to change out.. Make sure you get no dirt in the cspillary tube hole.brass screw end. The bulb must be just in the flame tip when adjusting. Good Luck, Ned-
Not finding what you are looking for?

1,364 views

Ask a Question

Usually answered in minutes!

Top Bosch Water Heaters Experts

john h

Level 3 Expert

29494 Answers

ZJ Limited
ZJ Limited

Level 3 Expert

17989 Answers

Brad Brown

Level 3 Expert

19187 Answers

Are you a Bosch Water Heater Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides

Loading...