no power to rc wire detected e73

Is your Nest thermostat showing no power to Rc wire detected e73 error, and you do not know how to fix it?

Below we have listed some common causes of this issue and how you can fix it. Kindly read on and understand these tips.

If the E73 Nest thermostat detects no power to Rc wire, it could be due to a low voltage on the Rc wire, dirty or clogged air filter or drip pan, and clogged drain tubes. Ensure that there is at least 24 VAC voltage on the Rc wire.

Also, replace the clogged air filter or drain tubes and remove any water in the drip pan.

Reasons for No Power to Rc Wire Detected E73

If your Nest thermostat shows this error, the reasons could be any of the following.

  • A low voltage on the Rc wire.
  • The drip pan has water.
  • The drain tubes are clogged.
  • The fuse is burnt        

Note: It is quite expensive to replace the Nest thermostat or any other HVAC system.

If you are not sure about troubleshooting its issue, kindly let an expert do it for you. You will spend less on an expert than buying a new thermostat.                                 

How to Fix Nest E73 No Power to Rc Wire Detected Error

fix no power to rc wire detected e73

You can apply these solutions to troubleshoot your Nest E73 thermostat with no power to Rc wire.

Kindly try from solution one till the error disappears.

Method 1. Check Wiring

Insecure and improper connections are major issues causing a lack of power to your E73 Nest thermostat RC wire.

Kindly inspect the wiring using these steps:

Step #1: Turn Off the Breaker

Begin by powering off the breaker by disconnecting the HVAC system from its power source.

The HVAC may have several breakers in the circuit. Ensure you turn all of them off.

Step #2: Detach Display

Detach the display from the thermostat from the base to reveal the connected wires. Locate the Rc wire, then disconnect it.

Please do not touch any other wire; only leave them as they were. Switch your thermostat to heat-only mode.

Step #3: Examine the Rc Wire

Once you remove the Rc wire, examine it. The wire should have about a millimetre of copper.

It should also be straight without any corners. Also, check that the wire is not painted over or corroded.

Step #4: Check the Wire’s Voltage

Using a voltmeter, kindly measure the voltage of the Rc wire. It should be consistent throughout the wire.

If the voltage is above 24 VAC, your Rc wire is fine. Hence, the problem is within the unit.

Note that most AC units fail during summer because of the hotter temperatures. So, this could be true with your system.

Step #5: Insert the Rc Wire

Once you confirm that your Rc wire is okay, insert it back to the connector.

Make sure that your thermostat’s connector button is pressed down.

Step #6: Check the Other Wires

You can also check the other wires to see if they have the same issue by performing the same check.

Switch on the breaker to turn on your thermostat, then insert it back into its base. Please wait for it to turn on.

Method 2. Check Your Thermostat’s Air Filter

A clogged air filter is one common cause of this problem. You should always ensure that your HVAC system gets enough airflow if you want it to function correctly.

If your air filter is clogged, it limits the amount of air that flows through the coils. When the air reaches the cooling coils, it freezes then possibly shuts down the system.

To solve it, locate your air filter. You will find your Nest thermostat air filter at the rear side of the grate, on the ceiling, or along the walls.

If the air filter is inside the furnace, you will have to turn off the breaker first. If your filter is clogged or dirty, replace it.

The problem can also be frozen cooling coils. Give them time to defrost first, then use them.

Always replace your air thermostat air filters after every three months to avoid such issues.

Method 3. Confirm If the Drain Tubes or Drip Pans Are In Good Condition

The system’s drip pan or drain tube carries frozen water away from the system. If they clog up, the water backs up.

In case of this issue, the heat pump or AC shuts down, and water fails to overflow. Hence, the HVAC system will not send power to the Nest thermostat, causing the error.

Steps to resolve the issue:

Step #1: Shut Off the Breaker

Turn off the breaker to shut off the HVAC system. If your system contains several breakers, remember to turn all of them off.

Step #2: The Cooling Coils

Find the cooling coils in the thermostat. You can refer to their location in the user’s manual.

The cooling coils might be behind the sealed panel. If so, do not remove the panel. If you remove the seal, the system will fail to work correctly.

Step #3: Check the Drip Pan                              

Confirm that the drip pan beneath the cooling coils has no water. Also, the drain tubes connecting the drip pan should not be clogged.

If you find water, then there might be a clog in the drain tubes. If you do not find water, check for rust which will show water presence in the system, but it has dried up.

Kindly check your HVAC system user guide for help removing the water or the clog.

Method 4. Check the Fuse

During the summer or hotter seasons, your AC system works harder compared to other cool seasons.

Sometimes, the extra performance can cause the system’s fuse to burn out. Hence, there will be a cut of power supply from the HVAC to the thermostat.

To fix the issue, turn off the breakers, then find the fuse on the control board of the HVAC system. If you cannot find it, kindly check for its location on your user’s guide.

Once you find the fuse, examine it. If you see any marks or discolorations, you will need to replace them.

After replacing the fuse, ensure that you return the panels you had removed then power on the HVAC system.

Method 5. Contact Nest Customer Support

If your Nest E73 thermostat detects no power error on the Rc wire, the above solutions are always the way to go, and they can fix it.

However, if you try all of them but nothing works, kindly contact Nest support.

You can explain to them the methods you have employed to solve the issue. Hence, you will help the support staff know the best way to approach the problem on your Nest thermostat.

When Nest e73 Nest detects no power to Rc wire, the wire has low voltage. Also, the system could have a clogged air filter, or the drip pan has water. Remove water from the drip pan, replace the clogged air filter and ensure the Rc wire has a higher voltage throughout the wire.

Read Next: How to Set Nest Thermostat to Hold Temperature?


If you’re experiencing no power to Rc wire detected e73 error on your Nest thermostat, use the tips above to fix the problem.

Employing the above troubleshooting steps should have the issue cleared, and your Nest thermostat work correctly again.

Just ensure that the fuse, the drip pan, and the air filter are in good condition. Kindly do not hesitate to seek assistance from a pro if you do not know how to apply the above steps.

Nicole B