How to Fix Nest No Power to Rc Wire? [Nest E73 Error]

Investing in a new Google Nest thermostat and facing no power issues is surely terrifying. So, are you here because your Nest showing an e73 error message, and you don’t know what to do next? For your ease, let me tell you this is nothing to worry about as you can easily fix it.

So, what does the Nest e73 error mean?

The e73 Nest error message directs toward some problem with the Nest’s wiring, which hinders the power supply to the thermostat. This ultimately causes the AC outdoor unit to break down and become non-functional. Extreme hot weather and low voltage on the Rc wire are its main causes.

Keep reading to learn the most common causes for Nest error e73 and some easiest hacks to fix it.

nest no power to rc wire

What causes Nest error e73?

There are various reasons for no power supply to the Rc wire resulting in the Nest e73 error. However, most of them are reversible and thus can easily be fixed. The most common cause for such an error is overworking your system, which may break down its AC unit.

Here are the causes for the Nest e73 error:

  • Extreme temperatures in hot weather may break down the AC unit, especially when the Nest overworks.
  • The burnt fuse may also interfere with your system’s power supply, resulting in the sudden abrupt shutdown of your Nest.
  • Water within the drip pan may create problems for you in so many ways. The most common of which is in the form of Nest error e73.
  • Low voltage on the Rc wire will obviously disrupt the power supply, resulting in such an error.
  • Clogged drain tubes have also shown this error in e73 in many ways.

How to fix the Nest e73 error?

To fix the Nest e73 error, follow a step-by-step guide. First, follow all the steps one by one until the problem gets resolved. Or the second option is first to recognize the main cause and then fix it accordingly.

Here are the steps to fix the Nest e73 error:

1. Check the wiring of your thermostat

The first hack is to ensure the wiring of your device has no defect and if it does, then resolve it at the earliest time possible for your ease.

Here are the steps to check the wiring of your thermostat:

  1. Firstly, switch off the HVAC system by turning off the breaker. Note that your system may have many such breakers, and you need to turn all of them off.
  2. Now remove your thermostat display from the base. Then just disconnect the Rc wire and not the other wires.
  3. Next, inspect the Rc wire by removing it first and exposing 1cm of the copper. Moreover, ensure that it’s straightened up before checking.
  4. Next, ensure there is no obstruction in the wire due to paint or any corrosion.
  5. Check the voltage of the Rc wire now using a voltmeter. Note that if the voltage is 24vac, only it will receive the power. So, if the voltage is adequate, the problem lies behind the AC unit.
  6. After inspecting all this, connect the wire back into your Nest device and press the connector button. Moreover, we would suggest you check the rest of the wires too.
  7. Now, turn the breaker on to enable the power.
  8. Lastly, put the thermostat back on the base and wait until the power gets on.

2. Check the air filters for any clogged material

Clogged-up air filters may block the airflow coming from the cooling coil. This would then freeze up the clogged substance resulting in your Nest shutting off. Therefore, it’s necessary to ensure air filters are not clogged to avoid inconvenience.

Here are the steps to check the air filters for any clogged material:

  1. Firstly, look for the air filter in the grate in your hallway.
  2. Turn off the power breaker of your system as you’ll be dealing with the wires, which can be dangerous.
  3. Next, look for any dirt, dust, or clog but ensure to do so gently.
  4. Turn off your Nest if the issue is the frozen coil, as they first need to thaw and melt out.

3. Check the drain tube/ drip pans for any clogged material

The drain tube/ drip pans may also clog up, which may cause the water to back up, resulting in its overflow. This will ultimately result in no power supply to the Nest thermostat, thus causing error e73.

Here are the steps to check the drain tube/drip pans for clogged material:

  1. Firstly, turn off the HVAC system by switching off the power using the breaker box.
  2. Now, look at the fan and furnace. Also, look at the linking lights, which may indicate that your system is still on.
  3. Now see if there’s water in the drip pan. If yes, then there is surely a clog.
  4. Further, ensure that there is no corrosion or water damage in your system.

If you find a clog in your drain tube/ drip pan, search on Google or take the help of the HVAC help guide to get rid of it. You may also contact a technician for this purpose.

4. Check the HVAC fuse

The HVAC fuse may burn due to excessive use in hot weather, especially when the filters are clogged up. As a result, there will be a hindrance in the power supply to your thermostat from the HVAC system.

Here are the steps to check the HVAC fuse:

  1. First, cut off the power supply to the HVAC system by turning off the breaker. If your system has multiple breakers, ensure to turn them all off.
  2. Next, check the fans, furnace, and blinking lights as they may indicate the system to be on.
  3. Now, look at the HVAC fuse present on the control board of your HVAC system. These fuses come in different shapes, so you may check the owner’s manual to find it out for your system.
  4. Now inspect the fuse carefully. If it’s discolored or blackened, it indicates that it’s damaged and needs to be replaced.
  5. Replace it if needed, and reconnect any panels you removed earlier to ensure your thermostat is working properly.
  6. Lastly, turn on the power at the breaker box.

5. Contact the customer support team

If none of the above hacks helped you, then feel free to contact the customer support team for their assistance. They’ll help you in the best possible way.

Tell them all the steps you have tried to resolve the problem. This will help them understand the issue in a better way. Thus, you’ll get rid of the problem more efficiently.


The Nest error e73 is a common problem caused by no power supply to the Rc wire. This occurs mainly due to extremely hot temperatures, burnt fuse, low voltage to the Rc wire, and much more. Note that all the causes for such an issue are reversible and can easily be fixed.

All you need to do is rule out the main cause behind such an error. To do so, follow this step-by-step guide to ensure all the equipment in the thermostat has no defect that can cause such an annoying problem at your end.

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