Thermocouple
Common pilot and ignition part on gas water heaters.
Rinnai Error Code 16 — What It Means
Error code 16 on a Rinnai tankless water heater indicates the combustion fan (also called the exhaust blower or induced draft fan) is not operating within the expected speed range. The control board monitors fan RPM via a Hall effect sensor on the fan motor. If the fan runs too slow, too fast, or not at all, code 16 is displayed and the unit shuts down — without confirmed fan operation, the board will not open the gas valve.
Common Causes
- Failed fan motor — The fan motor bearings seize or the motor windings fail, preventing the fan from reaching target RPM.
- Blocked fan or flue — Debris, bird nests, or ice blocking the exhaust cap or the fan housing prevents the fan from spinning at speed even with a working motor.
- Fan speed sensor (Hall effect) failure — The magnetic RPM sensor reports incorrect speed data to the board even if the motor is physically running correctly.
- Control board fan drive failure — The board’s fan motor driver circuit can fail, cutting power to the fan motor or misreading fan speed.
Step-by-Step Fix
- Check the exhaust vent termination — Go outside and verify the exhaust cap is clear of ice, debris, and bird nests. On Direct Vent models, check both the exhaust pipe and combustion air intake.
- Power cycle the unit — Turn the unit off and on at the power switch. For temporary fan stalls (vibration loosened a connector), a power cycle will clear code 16.
- Inspect the fan for physical obstruction — With power off, access the combustion fan (typically in the rear or top of the unit). Manually spin the fan wheel — it should rotate freely and smoothly. Resistance or grinding indicates bearing failure.
- Check fan motor power — During a heat demand attempt, verify voltage is present at the fan motor connector (typically 120VAC or DC depending on model). Voltage present but fan not spinning = failed motor. No voltage = board or wiring issue.
- Replace the combustion fan — If the motor is confirmed failed, replace with the Rinnai OEM fan assembly for the specific model (V53e, RU199, RLX94, etc.). Wiring connections vary by model.
Parts Often Needed
| Part | Notes |
|---|---|
| Combustion fan motor assembly | Rinnai OEM; must match model (V-series vs. RU-series differ) |
| Fan speed sensor | Hall effect sensor; often integral to the motor assembly |
| Control board (PCB) | Replace only if board fan driver is confirmed failed |
Need Replacement Parts?
Before ordering, match the water-heating part to the model number, electrical rating, and failure symptom. Check current prices on Amazon - prices and availability change frequently.
When to Call a Pro
Gas appliance fan replacement involves working inside the combustion enclosure. If you are not confident in safely accessing the combustion section and verifying electrical circuits, have a Rinnai-authorized technician service the unit.