Why does my tankless water heater keep short cycling?
Tankless water heaters short cycle when flow rates drop below the activation threshold or when internal components like blower motors malfunction, leaving homeowners with intermittent hot water. Manufacturers often refuse direct homeowner support and require certified contractors, forcing users to troubleshoot complex mechanical issues independently.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
- 1change flame rod
- 2change the water flow sensor into the heat chamber
- 3replacing the blower motor
- 4replacing the thermostat
- 5replacing the capacitor
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
“Recently, I noticed the unit is short cycling (see video with sound).”source ↗
“if we turn on the water for the tub which is pulling 2.5gpm, after a while we get cold water.”source ↗
“I tried calling Navien but they won’t talk to homeowner about it and require a contractor.”source ↗
“After some troubleshooting, I thought it may be the blower motor. I replaced the blower motor and it improved the amount of time it stays on, but overall, it still short cycles.”source ↗
Where this came up
People with this problem also raised
- 4How to trace an intermittent short circuit in a car wiring harness
- 6How to diagnose an intermittent equipment problem that only happened once
- 13Why is my truck shaking and popping after replacing wheel hubs?
- 23Intermittent car hesitation with no trouble codes
- 2Why keeps my car killing alternators with no visible electrical issue?
- 3Refrigerator stops cooling properly after being moved on its side