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Google’s Nest Thermostat is undoubtedly among the top programmable thermostats available on the market.
The Nest thermostat is extremely easy to set up and use, and most of the errors that may pop up are easily fixed.
However, there are a few errors that may seem almost impossible to fix. One such error is the E73 error which indicates that there is no power detected to the Rc wire.
A couple of weeks ago, I found my Nest thermostat starting to show issues.
It would shut down automatically, the screen would go black, and the air conditioner would not cool the house.
When I checked the thermostat’s display for any of the usual blinking lights, I saw the E73 error message and immediately decided to look it up online for some possible fixes to this problem.
After going through different articles and forums online, I compiled this list of troubleshooting options.
So what can you do if your Nest thermostat says no power to Rc wire?
To troubleshoot Nest Thermostat no power to RC wire, check your wiring, air filter, drain tubes/drip pans, and HVAC fuse and ensure that all of them are working correctly.
In this article, I will tell you about all the different possible causes that can cause your Nest thermostat to not detect power to the Rc wire.
I will also discuss how you can fix each of these potential issues to get your Nest thermostat back up and running again.
Check Your Thermostat Wiring
The most common issue that causes the E73 error is improper or unsecured connections.
You can check your wiring by following the steps below:
- Disconnect your HVAC system from power by turning off your breaker. Your HVAC system might have multiple breakers throughout the circuit, so ensure all of them are turned off.
- Detach your thermostat’s display from the base to reveal the wires connected to it. Disconnect the Rc wire while maintaining all the other wires as they were, switching the thermostat to heat-only mode.
- Remove the Rc wire and examine it. Ensure that it has at least 1 mm of copper exposed and that the copper is not bent. Make sure the wire isn’t corroded or painted over.
- Using a voltmeter, test the Rc wire to check that the voltage across the wire is consistent. A 24 VAC voltage indicates that your wiring is fine and that the problem is within the AC unit itself. This is common as a lot of AC units fail during the summer due to hotter temperatures.
- Insert the wire back into the Nest connector while ensuring that the connector button stays pressed down.
- To be thorough, you can perform the same checks on the other wires as well.
- Turn your breaker back on to bring back the power.
- Insert the Nest thermostat back into the base and wait for it to power back up.
Check The Air Filter Associated With Your Nest Thermostat
Another common issue that can cause this problem is a clogged air filter.
Maintaining proper airflow is paramount for your HVAC system to function properly, and a clogged air filter can severely limit the amount of air flowing through the cooling coils, which can, in turn, freeze and shut the system down.
To check your air filter:
- Locate the air filter on your system, usually found behind a grate along the walls or ceiling. The air filter can also be located inside your furnace, and in that case, you will have to turn off the power at the breaker first.
- If the filter is dirty or clogged, replace it.
- However, if the problem is frozen cooling coils, allow the coils to defrost before using them again.
It is recommended to replace air filters once every 90 days to prevent issues of this kind.
Check The Drain Tubes/Drip Pans For Your HVAC
Sometimes, the drip pan or drain tube that is supposed to carry condensed water away from the HVAC system can clog up, causing water to back up.
When this happens, your AC or heat pump will shut down to prevent a water overflow, causing your HVAC system to stop sending power to your Nest thermostat, which can cause it to display the E73 error.
To resolve this issue, follow these steps:
- Shut off power to the HVAC system by turning off the breaker. In case the system has multiple breakers, ensure they are all turned off.
- Locate the cooling coils; you can look for information online or in the user’s manual of your HVAC system. If the cooling coils are located behind a sealed panel, do not remove the panel yourself as the system may not work properly without the seal.
- The drip pan is usually found under the cooling coils, connected by plastic drain tubes. Ensure that there is no water in the drip pan and that the drip tube is not clogged.
- In case you do find water, it indicates that there may be a clog. You can also look for any signs of water damage like rust that can indicate earlier water presence. Check online or your HVAC system’s water guide to get help cleaning your clogged drip tube.
Check Your HVAC Fuse
Usually, during hot weather, your AC has to work extra hard. In some cases, this can cause your fuse to burn out, cutting the power supply from your HVAC system to your Nest thermostat.
To troubleshoot this issue:
- Cut off power to the HVAC system by turning off the breakers.
- On the HVAC system control board, locate the HVAC fuse. If you have trouble finding it, refer to your owner’s manual.
- Examine the fuse. If you find it burnt or discoloured, it is damaged and needs to be replaced.
- Upon replacing the fuse, ensure that you reattach any panels you removed earlier before powering the HVAC system back on.
Contact Nest Support
Usually, the steps above are guaranteed to fix the E73 error. However, if none of them work for you, it may indicate a problem with your Nest thermostat.
In this case, contact Google Nest Customer Support and inform them of your problem.
Make sure you mention all the different troubleshooting steps you implemented.
This helps them get a better idea of the problem you are facing and allows them to get the help you need much quicker.
Getting Rid of The E73 Error
At first glance, an E73 error can seem overwhelming as it brings down your Nest thermostat completely, rendering it unusable until the error is fixed.
Because of this, your Nest Thermostat will Not Cool, and you’ll have to bear the stuffy weather.
There are simple troubleshooting methods that you can try yourself, like checking the breaker box and ensuring that the AC breaker is on.
However, others like checking the cooling coils and drip tubes are quite complex, and it is recommended that you seek the help of an expert.
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Frequently Asked Questions
What does E73 mean on a Nest thermostat?
The E73 error on your Nest thermostat indicates that there is no power detected to the Rc wire.
To fix this error, check your wiring, air filter, drain tubes/drip pans, and HVAC fuse and ensure that all of them are working correctly.
How long does the Nest thermostat take to charge?
Nest thermostats usually charge within half an hour when charging via USB but can require up to 2 hours to fully charge if the battery has been completely drained.
How do I check my Nest thermostat battery?
Press the thermostat ring to bring up the Quick View Menu. Navigate to Settings and select Technical Info.
Next, select Power and look for the number labeled battery.
