How To Replace Thermistor On Girard Tankless Water Heater

This guide on How to Replace the Thermistor On Girard Tankless Water Heater will walk you through a step-by-step procedure to replace the thermistor like a pro. 

Apart from this, I will describe how the thermistor works and what happens if it gets defective. Without further ado, let’s dive in. 

How To Replace Thermistor On Girard Tankless Water Heater?

Walk through these 8 simple steps to replace the thermistor on your Girard RV Tankless Water Heater:

1. Turn off the water supply to your Girard Tankless Water Heater.

2. Remove the access panel and locate the thermistors on the copper pipe of your water heater system. There are two thermistors on the Girard Tankless Water Heater- input or cold water thermistor and output or hot water thermistor. 

3. Identify the input and output thermistors. I attached an image below to help you detect the input and output thermistors: 

4. Once you detect the input and output thermistors, it’s time to remove the one that gets defective. Use an 11mm crowfoot wrench to unscrew the compression nut that holds the thermistor in place. 

5. Generally, the thermistor is sealed into the water systems with an O-ring. Use needle nose pliers to hold the thermistor firmly and pull it out of the fitting. Never try to discard or damage the O-ring. 

6. Follow the wire of the thermistor you are replacing and remove it from the control board. 

7. Install the new thermistor and secure it with the compression nut. Then, connect the thermistor wire to the control board. 

8. Turn on the water supply and check for leaks. 

Function of Input and Output Thermistors

Girard Tankless Water Heater has two thermistors- an input or cold water thermistor and an output or hot water thermistor. These thermistors will give the control board the exact incoming and outgoing water temperatures. 

With the information it receives from the thermistors, the control board will adjust the BTUs to the gas valve to meet the requirements of the set temperature of the UCP. 

If the thermistor is at fault, it will throw an error code E0 or E4 based on which temperature probe is at fault.  

For example, if the board senses the flow sensor is on while the output thermistor is open, the unit will give an E0 code. Similarly,  you can see the E4 code on the UCP (User Control Panel) if the control board senses the flow sensor is on when the input thermistor is open. 

Read Further:

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• Girard Tankless Water Heater Error Codes
• Girard Tankless Water Heater Troubleshooting
• How To Replace Thermistor On Girard Tankless Water Heater

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Get a voltmeter and verify that the resistance of the thermistor is not an open circuit or a short if an E0 or E4 fault occurs. Also, ensure that the wire connections are good. 

FAQs

What is the error code 3 on a Girard Tankless Water Heater?

The error code 3 on the Girard Tankless Water Heater indicates the ECO thermostat opens. It occurs when the outlet water temperature exceeds 79°C. 

What is the E2 error code on Girard?

Flame sensing interrupted during normal operation is what the error code E2 means on the Girard Tankless Water Heater. This code will appear on the UCP for the same reason as the E1 code. Read this article on Girard Tankless Water Heater Code E1 to learn more about this. 

What is the E4 code on the Girard Tankless Water Heater?

E4 code on the Girard Tankless Water Heater means the input thermistor is at fault. It occurs due to a short or open circuit of the input thermistor. 

End-Note

Replacing the thermistor on the Girard Tankless Water Heater is simple. Go along with the simple eight steps I mentioned above and have the thermistor replaced like a pro. Good Luck!