Rinnai tankless water heater code 71: meaning and exact next steps

Reset the water heater's power once.

Rinnai's checks: the dip switch on the PC board is in the OFF position, the gas control wire is not loose or damaged, the heater circuit is not grounded, and if these are fine, replace the PC board.

Code 71 means a fault in a gas solenoid valve circuit (SV0 to SV4). Switch the heater off and on once. Moisture inside the gas valve can cause it, which means the valve needs replacing.

Use the controller's power key or the isolating switch to switch the heater off. Write down that code 71 appeared, the time and whether any hot water had been running. A code 71 means the heater has found a fault in the solenoid valve circuit, which controls the gas.

Switch the heater back on after a minute and open a hot tap. If the code does not return, record the date. If it returns, do not keep restarting, because the valve circuit has a fault that a reset will not remove.

Rinnai's checks include whether a dip switch on the PC board is in the wrong position, whether the gas control wire is loose or damaged and whether the heater circuit is grounded. All of these require opening the heater, which is not an owner task, and a wrong dip setting can stop the heater working.

A solenoid valve controls the gas flow, so any smell of gas is a reason to close the gas valve to the heater, leave the building and call the gas utility from outside.

Give a licensed technician the heater's model number, the code and the checks you made. Rinnai's last step, if the wire and switch are fine, is to replace the PC board, so ask for the fault to be confirmed with a meter first.