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My propane Rinnai was installed 6 years ago, it's been cleaned regularly, and worked without issue until last fall. Then it failed to light several times (code 14), always fixing itself after 12 - 24 hours. Finally, it wouldn't light off at all. My plumber, troubleshooting on the phone with Rinnai, determined the problem to be a thermal fuze failure. Rinnai sent a replacement, it was installed, and the unit was back on line. One month later, code 14 again. Same discussions with Rinnai, they suggested a heat exchanger replacement, and a new part was sent. While waiting for the part, after being off-line for 3-4 days, it fixed itself again - and lasted 3 more weeks until another code 14 failure. The new heat exchanger was installed. It worked for 4 months, then failed for two days, but again fixed itself for a week. Now I'm waiting for the plumber once again. Vents, gas pressures, water flow - all have been checked many times. The plumber and I are at wits end. It's basically a new unit except for the motherboard, and I've spent $900 so far. I'm ready for a plain electric tank. Any thoughts?