Rinnai Tankless Error Code Troubleshooting

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Categories Water Heating
Let us help you understand Rinnai tankless error codes and how to troubleshoot them.

Are you the proud owner of a Rinnai tankless water heater? When they work as they should, they’re great, but what happens when the heater says, “No”? Here, we will look at the Rinnai tankless error codes and what they mean.

Some might just be a case of resetting everything, while others indicate you need to call a Rinnai specialist.

Let’s look at where to find the error codes, what they mean, and whether you can fix them yourself or need to call a service engineer or plumber.


Where Will I Find the Error Codes?

These smart household appliances have a self-diagnostic tool built in that checks it’s operating as it goes. When something goes wrong, it shuts itself off and displays an error code.

On the MC-91, MCC-91, and MC-502 the error code will display on the temperature panel. On the MC-100 and BC-100, it will flash on the clock display.

When an error code appears you can usually follow a few simple steps and resolve the issue. However, bear in mind the complexity of the design — you might be better off calling a qualified technician.

Rinnai Tankless Error Codes

Time to look at the error codes, what they mean, and how they can be fixed.

Error Code 02

What It’s Telling You

The Solution

  1. Place a call for service at 1-800-621-9419.

Error Code 03

What It’s Telling You

  • The power has been interrupted during an automatic bath fill. If this happens when the power returns, this function won’t work.

The Solution

  1. Turn off the faucets: Turn off the all the faucets in the house.
  2. Reset the appliance and the code: Locate the On/Off button and press it twice.
  3. A fault with the PC board: If the code reappears then you might need to replace the PC board.

Error Code 05

What It’s Telling You

  • There’s a fault on the bypass servo if the model has bypass valves fitted.

The Solution

  1. Disconnect the power supply: Turn the power supply off and then on.
  2. Turn on the hot water: Open a hot water faucet and the appliance should fire up.
  3. Replace the bypass valve: If the code reappears, the bypass valve is faulty and needs to be replaced.

Error Code 07

What It’s Telling You

The Solution

  1. Check the power supply: Make sure the heater power is turned on.
  2. Is the water supply on? Make sure that your water to the unit is turned on and at a minimum 30 psi.
  3. Check the wiring: Ensure there are no damaged or loose wires in the pump harness.
  4. Check the water filter: Look for blockages and clear them.
  5. Flush the heat exchanger: Follow your owner’s manual to flush build-up from the heat exchanger.

Error Code 10

What It’s Telling You

  • Exhaust or air supply blockage.

The Solution

  1. Check the vents: Ascertain that only the manufacturer’s venting materials are in use, there are no obstructions, and the clearances and limits are correct.
  2. Improper installation: There’s a high chance the vent pipe has not been installed correctly.

Error Code 11

What It’s Telling You

  • There’s a fault with the ignition.

The Solution

Assuming that the gas pressure and type are correct, and your gas supply is on with no air in the system, check the following:

  1. Check the igniter: Make sure a spark is generated.
  2. Examine the wiring: Check that the connections in the wiring are correct.
  3. Is the unit grounded? Double-check the heater is grounded properly.
  4. Dip switches: Have they been set correctly?
  5. Check the valves: Ensure that the gas solenoid valves are not open or have short circuits.
  6. Inspect the burners: Make sure they are correctly seated and are not clogged with dirt or debris.

Error Code 12

What It’s Telling You

  • The flame has failed.

The Solution

Assuming that the gas pressure and type are correct and your gas supply is on with no air in the system, check the following:

  1. Check the PC board wiring: Ensure there are no loose or damaged connections.
  2. Power supply: Make sure there isn’t a loss or dip of power supply.
  3. Flame rod: Confirm that it’s connected and has no build-up of carbon.
  4. Gas solenoid valve: Verify it’s not short-circuiting.
  5. The burner: Clean any debris that has built up.

Error Code 13

What It’s Telling You

  • Abnormality in combustion.

The Solution

  1. Venting system: Make sure it’s correctly installed.
  2. Dip switches: Check they’re correctly set.
  3. Is there gas? Verify the gas supply to the appliance is on.
  4. Correct pressures: Make sure the low/high fire pressures are set properly.

Error Code 14

What It’s Telling You

  • A fault with thermal fuse.

The Solution

  1. Look for blockages: Check for obstructions in the venting, airflow and water flow.
  2. Check the heat exchanger: Make sure it’s working.

Error Code 16

What It’s Telling You

  • A warning that the appliance has overheated.

The Solution

  1. Look for blockages: Make sure venting and airflow are not obstructed. Also check the exhaust pipe, heat exchanger, and combustion chamber.
  2. Test the water flow: Establish it’s sufficient to prevent short cycling.

Error Code 19

What It’s Telling You

  • A fault with electrical grounding.

The Solution

  1. Test all components of the water heater for electrical short circuits (1).

Error Code 25

What It’s Telling You

  • The trap for condensate is full.

The Solution

  1. Drain line: Check for a blockage in the condensate line.
  2. Ascertain the air gap: Make sure there’s a gap between this line and where the drain line leaves the unit.
  3. Check for damage: Look for any loose, damaged or broken connections between the condensate sensor and PC board.
  4. Error code persists: If the tank drains properly and the error code is still there, change the condensate sensor.

Error Code 30

What It’s Telling You

  • Detection of flammable vapors.

WARNING!

If this happens, call in professionals to check the area is safe and free from flammable vapors before proceeding with any maintenance (2).

The Solution

  1. Check for damage: Check the sensor for damage or loose connections.
  2. The code reappears: Once the system has been restarted, if the problem persists, replace the sensor for flammable vapor.

Error Code 31

What It’s Telling You

  • Burner sensor (thermocouple) failure.

The Solution

  1. Check the manifold and dip switches: Make sure the manifold for low or high fires and the dip switches are correctly set.
  2. Test the thermocouple: Check the specification range of milli-volts is at the right level.
  3. Replace the part: If all else is in order, change the burner sensor.

Error Code 32

What It’s Telling You

  • A fault with the outgoing water sensor (thermistor).

The Solution

  1. Look for damage: Check sensor for loose or damaged connections.
  2. Check the ohms: Ensure resistance readings are within specifications.
  3. Descale: Clean any scale from the sensor.
  4. Renew the part: Replace sensor.

Error Code 33

What It’s Telling You

  • Outgoing heat exchange temperature sensor fault.

The Solution

  1. Check for damage: Make sure there are no loose or damaged sensor connections.
  2. Test resistance: Check the readings are within specifications.
  3. Descale: Clean any build up.
  4. Renew the part: Replace sensor.

Error Code 34

What It’s Telling You

  • Faulty air temperature sensor for combustion.

The Solution

  1. Check for damage: Look for loose or damaged sensor connections.
  2. Test resistance: Make surethe sensor is within specifications.
  3. Descale: Clean any build-up from the sensor.
  4. Examine the fan blade: Is it on tight and in good condition?
  5. Change the part: Replace sensor.

Error Code 35

What It’s Telling You

  • Faulty tank temperature sensor.

The Solution

  1. Check for damage: Look for loose or damaged sensor connections.
  2. Resistance: Make sure readings are within specifications.
  3. Clean: Remove build up on the sensor.
  4. Change the part: Replace sensor.

Error Code 52

What It’s Telling You

  • Faulty modulating solenoid valve (POV) signal.

The Solution

  1. Inspect for damage: Look at the valve connections for loose or broken wires.
  2. Resistance: Make sure readings are within specifications.
  3. Check the voltage: Ensure it’s correct for the POV valve when the unit is firing up.
  4. Change the PC board: If the voltage is correct and the error code remains, change this board.

Error Code 58

What It’s Telling You

  • Faulty secondary heat exchanger.

The Solution

  1. Damage: Check for broken or loose sensor connections.
  2. Descale: Inspect the heat exchanger and clean or flush it according to your owner’s manual.
  3. Prevent future scale build-up: Treat hard water.

Error Code 61

What It’s Telling You

  • Faulty fan motor for combustion.

The Solution

  1. Check for damage: Look for broken or loose connections on the wiring harness for the fan.
  2. Check for free movement: Make sure the fan moves freely and the blower is intact.
  3. Obstructions: Inspect the fan housing and ensure nothing is impairing movement.
  4. Winding resistance: Ensure the levels of the fan are correct.
  5. Replace parts: If there are issues with the fan, change it out. If the fan is good, renew the PC board.

Error Code 65

What It’s Telling You

  • Fault in the water flow control. The water flow control valve hasn’t closed when using the bath fill function.

The Solution

  1. Disconnect the water: Turn off water and discontinue the fill function immediately.
  2. Call for service: Get the unit serviced by a qualified professional.

Error Code 70

What It’s Telling You

  • Faulty PC board.

The Solution

  1. Damage: Check for broken or loose connections on the PC board.
  2. Dip switches: Ensure they’re correctly set.
  3. Renew parts: Replace PC board.

Error Code 71

What It’s Telling You

  • Faulty solenoid valve circuit.

The Solution

  1. Damage: Check for broken or loose connections on the SVO through to SV4 solenoids on the gas valve.
  2. Moisture: Ensure there’s no moisture in the plastic tubes on internal units.
  3. Renew the gas valve: If there is moisture, replace the gas valve.
  4. Resistance: Check and measure the ohms.
  5. Replace parts: If the above doesn’t work, you need a new PC board or gas valve.

Error Code 72

What It’s Telling You

  • Faulty flame sensing device.

The Solution

  1. Damage: Check for broken or loose connections on the flame rods.
  2. Flame rod: Make sure this rod touches the flame when it fires. Remove and inspect it, cleaning carbon build-up if necessary.
  3. Burner: Check for debris, which might cause a short circuit.
  4. Parts replacement: Flame rod gasket, flame rod, and control board.

Error Code 73

What It’s Telling You

  • Faulty burner thermocouple.

The Solution

  1. Damaged burner thermocouple wires: Check for broken or loose connections.
  2. Dip switches: Make sure they are correctly set.
  3. Replacement parts: Control board or burner thermocouple.

Error Code 79

What It’s Telling You

The Solution

  1. Damage: Check for broken or loose connections to the leak sensor.
  2. Water leaks: Inspect the piping and heat exchanger. If there aren’t any leaks, dry out the cabinet and the leak sensor and restart the unit.
  3. The error code is still showing: Disconnect the sensor and start the heater.
  4. Replace parts: If the appliance works without the sensor, replace this component.

Error Code FE

What It’s Telling You

  • Detection of flammable vapors.

WARNING!

Before starting any work on the appliance, call in professionals to check the area is safe and free from flammable vapors.

The Solution

  1. Damage: Make sure the sensor for flammable vapors is intact and has no broken or loose connections.
  2. Restore power: When you’re sure that flammable vapors aren’t present, turn the gas and power on.
  3. Check the system: Open a hot water faucet to start the heater up.
  4. The code has not cleared: Change out the sensor and, if necessary, the control board.

Error Code FF

What It’s Telling You

  • The system has had a repair or maintenance carried out.

The Solution

  1. When a qualified technician services or carries out maintenance on your water heater, this code will be shown. This way you can identify new codes that appear after a service. The system will store the last nine error codes. To access them, push and hold the on/off button and use the up/down buttons to scroll.

Error Code LC

What It’s Telling You

  • Build-up of limescale.

The Solution

  1. Check your manual: Follow the manufacturer’s recommended procedure for flushing the system.
  2. Temporary reset: You can reset the code on a temporary basis by pushing the button for on and off five times. This will allow the heater to work for about 70 hours before initiating the code again, which stops the unit working again.

Time to Troubleshoot

Next time a Rinnai tankless error code appears you’ll be able to decipher what it means and what you need to do.

SAFETY FIRST

It’s important that any time a code indicates flammable vapors are present, you don’t work on your heater. You must call a professional to ensure the area is safe first.

The fixes are not always straightforward and there are times when you should call a qualified professional to deal with them. This could also be the case if you’re not comfortable carrying out any maintenance yourself.

We hope you found this guide useful and informative. Please leave us a comment with your own thoughts and experiences, and don’t forget to share this with someone who’s also trying to decipher their Rinnai!

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About the Author

Peter Gray

Peter has been a homeowner for 35+ years and has always done his own repair and improvement tasks. As a retired plumber, Peter now spends his time teaching others how they can fix leaks, replace faucets, and make home improvements on a budget.
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