What causes Rinnai Tankless Water Heater 71?

Loose, broken or damaged wiring harness connections between the gas solenoid valves (SV0 to SV3) and the PC board. On some models, the single DIP switch on the PC board not set to off, or a grounded heater circuit, both of which Rinnai lists in its code 71 checks. Moisture in the plastic tubing from the bottom of the combustion box to the gas valve on indoor models, which Rinnai links to a leaking heat exchanger or vent condensation running back into the heater. A solenoid valve coil that has failed open (no resistance reading). A mechanical obstruction inside the gas control valve, which Rinnai says can cause code 71 even when the coil resistances are good. A failed PC board.

When should I call a pro for Rinnai Tankless Water Heater 71?

Following Rinnai's first code 71 procedure (SENSEI and non-SENSEI): confirming the single DIP switch on the PC board is off, checking the gas solenoid valve harness back to the PC board, measuring the gas solenoid valve resistance or voltage at the board connector against Rinnai's spec, making sure the heater circuit isn't grounded, then replacing the gas valve and, last, the PC board. Following Rinnai's second code 71 procedure for the SV0 to SV3 solenoid valve fault: with electrical, gas and water supply turned off, checking the wiring harnesses to SV0, SV1, SV2, SV3 and SV4 for loose, broken or damaged connections back to the PC board. On indoor models, checking the plastic tubing from the bottom of the combustion box to the gas valve for moisture. Rinnai says to replace the gas valve if moisture is found, then pull the burner manifold and burner to find the source: replace a leaking heat exchanger and any parts it damaged, or add a condensate drain at the top of the heater if vent condensation is running back in. Checking voltage to SV0 and SV1 while the heater is trying to fire. Measuring the resistance of each solenoid coil against the technical data sheet under the front cover. Rinnai says to replace the gas valve and burner manifold if any solenoid reads open. Replacing the gas control valve if code 71 persists with good coil readings, since Rinnai notes a mechanical obstruction inside the valve can still cause it. Replacing the PC board as the last step. On SENSEI models, transferring settings from the old board with the data transfer cable that ships with the new board, or programming the parameters manually.

Code: 71🚿 Rinnai Tankless Water Heater

Rinnai Tankless Error Code 71: Gas Solenoid Valve Circuit Fault (Meaning, Causes, Fixes)

Q: What does Rinnai Tankless Water Heater 71 mean?

Code 71 on a Rinnai tankless water heater means a fault in the gas solenoid valve circuit: the control board isn't getting a proper response from the solenoid valves (SV0 to SV3) that open the gas to the burner. It is an electrical and gas valve fault, not a venting or gas supply problem, so there's very little a homeowner can do beyond a power reset. Rinnai's repair steps (harness checks, coil resistance, gas valve or PC board replacement) are for a licensed professional. Rinnai's VA Indoor Installation and Operation Manual defines code 71 as SV0, SV1, SV2, and SV3 Solenoid Valve Circuit Fault, and the V53De manual lists it as Solenoid Valve Circuit. These solenoid valves sit on the heater's gas control valve and burner manifold and open gas to different burner stages, so the PC board needs to drive each one and see a proper circuit. Rinnai's Troubleshooting Tankless Water Heater Diagnostic Codes manual, which applies code 71 to SENSEI and non-SENSEI models, lists the causes in order: loose, broken or damaged wiring between the solenoids and the PC board; moisture in the plastic tubing that runs from the bottom of the combustion box back to the gas valve on indoor models, which Rinnai traces to a leaking heat exchanger or condensation running back down from the vent; a solenoid coil that reads open; a mechanical obstruction inside the gas control valve even when the coil resistances look good; and finally a failed PC board. The correct resistance values are printed on the technical data sheet under the heater's front cover, not in the owner's manual. Code 71 is different from code 52 (the modulating solenoid valve signal) and code 72 (flame sensing device).

Reviewed 2026-10-23 · Based on 3 manufacturer & service sources

What the code means

Rinnai's VA Indoor Installation and Operation Manual defines code 71 as SV0, SV1, SV2, and SV3 Solenoid Valve Circuit Fault, and the V53De manual lists it as Solenoid Valve Circuit. These solenoid valves sit on the heater's gas control valve and burner manifold and open gas to different burner stages, so the PC board needs to drive each one and see a proper circuit. Rinnai's Troubleshooting Tankless Water Heater Diagnostic Codes manual, which applies code 71 to SENSEI and non-SENSEI models, lists the causes in order: loose, broken or damaged wiring between the solenoids and the PC board; moisture in the plastic tubing that runs from the bottom of the combustion box back to the gas valve on indoor models, which Rinnai traces to a leaking heat exchanger or condensation running back down from the vent; a solenoid coil that reads open; a mechanical obstruction inside the gas control valve even when the coil resistances look good; and finally a failed PC board. The correct resistance values are printed on the technical data sheet under the heater's front cover, not in the owner's manual. Code 71 is different from code 52 (the modulating solenoid valve signal) and code 72 (flame sensing device).

Likely causes

Loose, broken or damaged wiring harness connections between the gas solenoid valves (SV0 to SV3) and the PC board
On some models, the single DIP switch on the PC board not set to off, or a grounded heater circuit, both of which Rinnai lists in its code 71 checks
Moisture in the plastic tubing from the bottom of the combustion box to the gas valve on indoor models, which Rinnai links to a leaking heat exchanger or vent condensation running back into the heater
A solenoid valve coil that has failed open (no resistance reading)
A mechanical obstruction inside the gas control valve, which Rinnai says can cause code 71 even when the coil resistances are good
A failed PC board

Safe DIY checks

⚠ Before you start

Unplug the appliance and shut off its gas valve before working on it; never disconnect or alter the gas line. If you smell gas, leave and call your gas utility.

Write down the code and your model and serial number from the rating plate. A pro will want both, and Rinnai's repair steps depend on the model.
Turn the heater off at its power switch or unplug it, wait a minute, and power it back on, then open a hot water tap to see whether 71 returns. Rinnai's code stops showing once the fault is corrected and the heater supplies hot water.
Look around the bottom of the heater and the vent connector for water, rust trails or drips. Rinnai ties moisture in the gas valve tubing to a leaking heat exchanger or condensation running back down the vent, so tell the technician if you see any.
Don't open the gas valve or burner area yourself. Rinnai's code 71 steps involve turning off electrical, gas and water supply and measuring the gas valve circuit, which is licensed-professional work.
If 71 keeps coming back, call a licensed professional or Rinnai. If the heater is under warranty, contact Rinnai or a Rinnai-authorized technician before anyone replaces parts. If you smell gas at any point, leave the house and call your gas company from outside.

🛠 When to call a pro

Following Rinnai's first code 71 procedure (SENSEI and non-SENSEI): confirming the single DIP switch on the PC board is off, checking the gas solenoid valve harness back to the PC board, measuring the gas solenoid valve resistance or voltage at the board connector against Rinnai's spec, making sure the heater circuit isn't grounded, then replacing the gas valve and, last, the PC board.
Following Rinnai's second code 71 procedure for the SV0 to SV3 solenoid valve fault: with electrical, gas and water supply turned off, checking the wiring harnesses to SV0, SV1, SV2, SV3 and SV4 for loose, broken or damaged connections back to the PC board.
On indoor models, checking the plastic tubing from the bottom of the combustion box to the gas valve for moisture. Rinnai says to replace the gas valve if moisture is found, then pull the burner manifold and burner to find the source: replace a leaking heat exchanger and any parts it damaged, or add a condensate drain at the top of the heater if vent condensation is running back in.
Checking voltage to SV0 and SV1 while the heater is trying to fire.
Measuring the resistance of each solenoid coil against the technical data sheet under the front cover. Rinnai says to replace the gas valve and burner manifold if any solenoid reads open.
Replacing the gas control valve if code 71 persists with good coil readings, since Rinnai notes a mechanical obstruction inside the valve can still cause it.
Replacing the PC board as the last step. On SENSEI models, transferring settings from the old board with the data transfer cable that ships with the new board, or programming the parameters manually.

Parts that commonly fix it

Always match the part number to your exact model.

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Combustible gas leak detector

For peace of mind around a gas water heater. Any real gas smell means leave and call the gas company, not a DIY check.

[affiliate link slot: AFFILIATE_SLOT_GAS_LEAK_DETECTOR]

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Digital multimeter

What a technician uses to measure the solenoid coil resistances. Rinnai's values are on the data sheet under the front cover.

[affiliate link slot: AFFILIATE_SLOT_MULTIMETER]

Sources

Last reviewed 2026-10-23. Always confirm against the manual for your exact model number.

Rinnai Tankless Error Code 71: Gas Solenoid Valve Circuit Fault (Meaning, Causes, Fixes)

What the code means

Likely causes

Safe DIY checks

🛠 When to call a pro

Parts that commonly fix it

Combustible gas leak detector

Digital multimeter

Related codes

Sources