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Bosch Tankless Water Heater - EA Error code; Help!

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  • Jul 8th, 2012 12:11 am
[OP]
Newbie
Apr 14, 2007
9 posts
Mississauga

Bosch Tankless Water Heater - EA Error code; Help!

I need some advice here. Have a Bosch Tankless Water Heater for slightly over three years now. First time, a Reset doesn't resolve problem of no hot water. EA error code shown, where code description is "No Flame ionization detected with water flow". Had a technician come in for Service and he debug it to motherboard!! Now have to wait till manufacturer ship it and then have to pay tech to install. Good grief. What are my other options? Is it the real cause? Anyone has similar experience?

He opened and checked different parts in the heater machine and everything looked fine, and he also tested with a new heat sensor(?) but to no avail. No hot water for a week, well at least it is summer but still...
7 replies
Deal Guru
Jan 27, 2006
10679 posts
4236 upvotes
Vancouver, BC
unleash88 wrote:
Jul 6th, 2012 7:17 pm
I need some advice here. Have a Bosch Tankless Water Heater for slightly over three years now. First time, a Reset doesn't resolve problem of no hot water. EA error code shown, where code description is "No Flame ionization detected with water flow". Had a technician come in for Service and he debug it to motherboard!! Now have to wait till manufacturer ship it and then have to pay tech to install. Good grief. What are my other options? Is it the real cause? Anyone has similar experience?

He opened and checked different parts in the heater machine and everything looked fine, and he also tested with a new heat sensor(?) but to no avail. No hot water for a week, well at least it is summer but still...
Question - when you start the flow of water, does it attempt to light? Do you hear the igniter working? Do you see a flame?

I have a 12 year old Bosch unit (no motherboard) but the principles are the same.
[OP]
Newbie
Apr 14, 2007
9 posts
Mississauga
When I restart the Heater Tank, the pilot light comes on for a couple of seconds and then dies out. It does it 2-3 times before the EA error code kicks in. Any opening of hot water tap will just provide cold water. Hope that answers your question. Thanks for the quick reply. Just went out to buy a pail so that I can mix hot water with cold for showers. Sigh.
Deal Guru
Jan 27, 2006
10679 posts
4236 upvotes
Vancouver, BC
unleash88 wrote:
Jul 6th, 2012 8:49 pm
When I restart the Heater Tank, the pilot light comes on for a couple of seconds and then dies out. It does it 2-3 times before the EA error code kicks in. Any opening of hot water tap will just provide cold water. Hope that answers your question. Thanks for the quick reply. Just went out to buy a pail so that I can mix hot water with cold for showers. Sigh.
If the pilot light lights, then we know that:

1. the flow sensor is working (ie - it knows that water is flowing)
2. the gas flows
3. the igniter works

The pilot light warms up a sensor (the thermocouple) when it's lit. The thermocouple looks like a thick wire that sits in the middle of the flame. The thermocouple's job is to tell the system that the pilot light is lit so gas can proceed to the burners where the pilot light will then light. If the thermocouple isn't doing it's job, the pilot light will light as you see now and then go out after a couple of seconds because the thermocouple isn't sending the correct single back to the system.

You can try cleaning the thermocouple. The Bosch service guy told me that you can use weak abrasive like a new $5 bill and rub all of the surfaces that come in contact with the flame to clean it off. Don't use any chemicals or anything else to clean it off. I know when I made the mistake of cleaning it in the past, I had to use a pencil eraser to clean off the residue before my tankless would light consistently again.
[OP]
Newbie
Apr 14, 2007
9 posts
Mississauga
Thank you for your advice so far. Looked for thermocouple part and can only guess that Overheat Sensor (ECO) is equivalent. The technician tested the ignition group, even tho the pilot light comes on when started. I can send you the diagram, if only I can figure out how to attach diagrams to this thread. No success so far.
Deal Guru
Jan 27, 2006
10679 posts
4236 upvotes
Vancouver, BC
unleash88 wrote:
Jul 7th, 2012 9:54 am
Thank you for your advice so far. Looked for thermocouple part and can only guess that Overheat Sensor (ECO) is equivalent. The technician tested the ignition group, even tho the pilot light comes on when started. I can send you the diagram, if only I can figure out how to attach diagrams to this thread. No success so far.
You probably need to host the picture somewhere and point to it... That's what I've done in the past.

What's the model of the unit?
Deal Guru
Jan 27, 2006
10679 posts
4236 upvotes
Vancouver, BC
I can access those files.

First off - you can buy any parts you need from the distributor - Astrovan - http://www.astravan.com/. They are a small outfit here on the West Coast but they are great to deal with and will also help you troubleshoot over the phone.

Second - from reading some of the troubleshooting stuff and the installation guide, the unit should be trying to light 3 times before flashing the code. Also, a lot of the other Bosch tankless units use the same error codes so a fix for them might be a fix for you as well.

Third - have you tried the on-board diagnostics as pointed out in the manual?

Looking at the documents, it doesn't have much detail on the gas and the flow of the gas (I'm assuming that there is a service manual that goes into the detail). However, the ignition group (item 7 on page 52) probably contains the 3 parts needed for a pilot - gas outlet, igniter, sensor (thermocouple). That's where I would look. You might be able to get some instructions on the 'net on how to replace that piece which will show you how to get access to it. Be careful as you are dealing with a gas appliance.

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