Doug's Sounding Board

Short version: The on-demand water heater is working again.

Long version:
For most of the winter the on-demand water heater wasn’t paying attention to our demands. Sometimes it would take several tries to get hot water, sometimes it would come right away, sometimes it would never come. It seemed to work better with the cover off and seemed like it might be tied to the temperature outside (it’s an outside mounted unit).

We had a plumber that works on Takagi water heaters come out to try and figure out what was wrong. Various searches on-line turned up some people with similar problems but with no answers. The blink code from the heater itself indicated one of three things and I never purchased the remote temperature unit because I never saw a need to change the temperature once it was set. It turns out it’s more useful to let it tell you specific error codes. The plumber tore apart the unit and found everything looked good, even the heat exchanger which is usually the part that causes intermittent problems with hard water deposits.

The plumber called the Takagi support people. They conferred and the plumber came back another day (no extra charge) and he checked some more things and then called the Takagi guy and did some more things with him on the phone. Still no answers. The plumber called back a few days later saying there had been more conversations with the Takagi guy and they came to the conclusion that it was probably a little internal spinning part that was frozen with hard water deposits and that it needed to be flushed. I was skeptical because the gas was flowing and a spark could be seen which means everything is starting up normally, it just wasn’t actually igniting.

The plumber gave me the Takagi guy’s phone number and after telling him everything and saying I disagreed with the stuck part theory because it wouldn’t be so reliably related to temperature and it wouldn’t be affected by the front cover being off. The Takagi guy said I needed to check the spark by pulling off the ignition wire and holding it an inch from the manifold. I should see a nice blue spark but instead I saw nothing. At about 1/4″ I saw a weak orange spark. Takagi guy said the problem was the ignition wire and that I should try cutting an inch off the end and reattaching the connector. When I did that I realized the connector was glued on and wasn’t going to be reconnected. I jammed the end on to the terminal and sure enough it was more reliable, even without the normal connector on there. Unfortunately the cable was glued into the igniter as well so I needed a new igniter and cable. It was out of warranty so it was $42 including shipping and handling. The installation took five minutes and the new one has a cable that isn’t glued in which will be helpful if this happens in the future.