If you own a Rinnai tankless hot water heater, you may occasionally encounter Error Code 34. This pesky little code indicates a Combustion Air Temperature (CAT) Sensor Fault, which if ignored, can hinder your unit’s performance. But don’t worry—we’ve got you covered. Let’s explore together what a CAT sensor fault entails and how to get your Rinnai unit back up and running in no time.

Understanding a CAT Sensor Fault

The CAT sensor is a crucial component in Rinnai tankless water heaters. It plays an essential role in regulating the efficiency of the combustion process within the unit. It monitors the temperature of the combustion air, thereby ensuring that the system operates within the optimal temperature range. Any malfunction in this sensor can lead to improper combustion and reduce the efficiency of your Rinnai heater. Error Code 34 signals this sensor fault, which could be due to a variety of issues such as restricted airflow around the unit, damaged sensor wiring, an accumulation of scale on the sensor, or a compromised fan blade.

1. Check for Airflow Restrictions

Our first stop on this troubleshooting journey involves checking for airflow restrictions around the unit and the vent terminal. Think of your unit as a marathon runner—it needs plenty of air to perform its best! Blockages within the vent terminal or around the unit—usually from dust, debris, or even tiny critters—can mess up the combustion air temperature. So, get that inspection torch out and give these areas a thorough clean.

If you’re unsure whether your unit’s air flow is restricted, check for noticeable signs such as slowed heating or a weak blue flame in your heater. This could suggest that the air supply is inadequate. Be aware of any unusual noises coming from your unit, such as whistling or grinding. These could be signs of airflow obstruction.

2. Inspect the Sensor Wiring

Next on our list is the sensor wiring. Damaged, frayed, or loose wiring can play havoc with signal transmission from the sensor to the control unit, causing our Rinnai friend to misinterpret air temperature. Remember to switch off the system before doing your detective work on the wiring. And if you spot any damage, get it fixed pronto.

If the wiring appears damaged, but you’re unsure, you can use a multimeter to check the continuity of the wires. If the multimeter indicates an open circuit, that confirms the wire is broken and needs to be replaced.

3. Measure the Resistance of the Sensor

Thirdly, it’s time to bring out the multimeter and measure the resistance of the sensor. If the resistance reading isn’t within the range specified by Rinnai, then you may have found your culprit—a faulty sensor.

If you’re uncertain about whether the resistance reading from your sensor is within the manufacturer’s specified range, try reaching out to Rinnai customer support or your local technician with your model number. They should be able to provide you with the correct resistance range for your model.

4. Clean the CAT Sensor

Just like us, our Rinnai unit also needs a good scrub every once in a while, especially the CAT sensor. Dust, dirt, and scale accumulating on the sensor can skew the readings and lead to Error Code 34. So, get a soft brush or cloth and gently clean the sensor to keep it in top shape.

If you’re finding it difficult to clean the sensor because it’s in a hard-to-reach area or it appears to be heavily scaled, you may need specialized cleaning tools or solutions. It might also be the case that the sensor is too deteriorated and needs to be replaced. Be sure not to use any harsh or abrasive cleaning tools or chemicals that could damage the sensor.

5. Check the Fan Blade

Moving on, let’s ensure the fan blade is snug on the motor shaft and looking healthy. This fan is vital for regulating combustion air. Any signs of a loose or damaged blade could lead to issues with the combustion process.

If the fan blade is damaged or loose, it might also require a replacement to restore proper fit and function. If you’re having trouble inspecting the fan blade or if you’re unsure whether it’s tight on the motor shaft, it might be best to consult with a professional.

6. Replace the Sensor

Lastly, if our friend Error Code 34 is still hanging around after all these checks, it might be time to replace the CAT sensor. It’s a crucial part of the heating system and a faulty one can impact your Rinnai unit’s performance and safety.

Replacing the sensor can be a complicated task if you’re not familiar with your Rinnai water heater’s internal components. Always consult the user manual or reach out to a professional technician if you’re not comfortable performing this task. Remember, safety first!

We hope this troubleshooting section helps smooth out any bumps on your journey to resolving Error Code 34 on your Rinnai tankless water heater. Let us know in the comments if you’ve encountered any other issues not covered here, and how you’ve solved them.

In Conclusion

There you have it! You’re now equipped to tackle Error Code 34 and keep your Rinnai tankless water heater running smoothly. Remember, while this guide should help you identify and possibly resolve common issues, there’s no substitute for professional assistance. So, don’t hesitate to call in a trained technician when needed.

Drop us a comment below sharing your experiences with Rinnai Error Code 34. How did you resolve it? Did this guide help you? We’d love to hear from you!