We had been noticing that the hot water was becoming limited. It would get really hot, then cut out. Usually, you should be able to just turn it off, then on again, and it should resume heating; but now you'd have to leave it off for 10 minutes. Then a half hour. Then longer.
Remember that this is a tankless. The water flows through copper tubing over the gas flame and is quickly heated as it's being used. There is a sensor on the line which indicates whether the water has gotten too hot and sends this info to a computer chip which shuts it down.
Well, there had been a water leak on top of the heater, about 3 inches above it. Serious leak - the CPVC pipe had split. I replaced it, but the heater got pretty well soaked. I removed the batteries and thoroughly dried it out before attempting to use it again, but that was when the symptoms started. Or at least when they became really noticible and quantifiable. I'm thinking now, though, that water getting too hot may have been what made the pipe split.
I got really daring and took the front cover off. (WARNING: no user-servicible parts inside!) Looked it over. Turn on water, it sparks. No gas. How about this? I'll bet that's the heat sensor - what happens if I disconnect it? Many, many trips up and down the stairs.
I had long since lost the name and number of the on-line guy I got it from, but searching online got me to Omega2000, and I tried to find a diagram or something which would explain the workings of the things. Eventually I found the phone number and called, and sure enough it was the same person. I remembered him. His name is George, and he's Japanese. His English is rocky, but he knows his product, and to give him his due, he spent an hour and a half on the phone with me, having me try various things, testing different components. This is two years after I bought the thing. I'm not sure I like the tankless, it has it's problems, but I certainly have gotten my money's worth. He could have told me to take a flying leap.
He finally said that since I couldn't turn off the gas to just the heater, he couldn't have me take apart the solonoid to make sure that part worked. So I went out and bought parts, shut off the gas to the house, and installed a gas shut-off valve. Then tried to take the solonoid out. It wasn't cooperating. The screws just chewed up.
When Dale got home from work, we took the whole blinkin' thing apart, then drilled out the screws. Broke 5 drill bits. With the exposed solonoid in my hand, I could plug it in, trip the switch, and determine that indeed the plunger inside retracts as it's supposed to.
The next morning, I bought bolts to replace the screws, and we put it back together. It still didn't work: no surprise, since every part had been tested and was found to work. Which means that the only part left that can be bad is the computer chip.
I called George, told him my findings, and asked him whether I had put the spring back in right. He kind of had a fit. "No, no, no! You shouldn't have taken the whole thing apart! It it isn't back together right, you could have a bad accident! I'm going to send you a new gas assembly. Send me your address."
I reminded him that the part that was probably bad was the computer chip and that I was willing to buy one, so he told me where to find the parts list on the internet site. The computer chip is $50. The gas assembly which he is sending me (free) is $60. I paid the $20 for 3-day shipping. Probably will come on Monday.
At least I'm now confident that we will have hot water again at least by this time next week. It really shouldn't be difficult to put it back together now that I know what I'm doing.