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Nest Thermostat No Power To RC Wire: How To Fix Guide (2023)

Nest Thermostat No Power To RC Wire

Among all the available thermostats, I got my hands on one and only β€œNest Thermostat”. The reason for this choice is because Nest thermostats are top-rated in terms of performance, convenience, compatibility and smartness.

These are considered to be one of the top programmable thermostats because they are smart learners. They observe your routine patterns and prepare a schedule for you in return. But of course there are some issues which are associated with this thermostat as well.

Most of the fixes are easily solvable while some of them seem a bit difficult to solve. Even the difficult ones are easily solved, you just need to have some knowledge regarding them. My thermostat has been showing various errors like low battery warnings and delayed message error.

Other than this, I got to witness another error i.e. E73. I didn’t have any prior knowledge regarding this error so I decided to search it over the internet in order to get the issue resolved. Now I want to share that knowledge with you all because I want you all to have it the easy way.

Error E73 Indicates No Power To Rc Wire Nest. To Resolve This Issue It Is Must For You To Have A Thorough Check-up Of The Wiring, Drain Tubes, Air Filters And Lastly Hvac Fuse.


No power to RC wire detected issue can be resolved if you ensure the proper checking of the wiring, air filters, drain tubes and HVAC fuse. If any one of the following is faulty then chances are that you might see this error on your thermostat’s display.

In this article we will be discussing the reasons for the occurrence of this issue along with its fixes. So make sure you give this article a complete read till the end.


Following are the reasons for the occurrence of no power to Nest thermostat error.


The first and most common reason for this error has to be improper wiring of the thermostat. Sometimes this improper wiring also forms unsecured connections. You must check it in order to avoid various inconveniences associated with it.

nest thermostat faulty wiring


To check the wiring of your thermostat, follow the below mentioned steps.

STEP 1 – Turn OFF all the breakers to which your HVAC system is connected. Disconnect your HVAC system to continue the process
STEP 2 – Remove the face plate of your thermostat to have a clear look at the wires
STEP 3 – Now you have to disconnect the RC wire and make sure your thermostat is in the β€œHeat-Only” mode
STEP 4 – Do a thorough checkup of the RC wire i.e. check whether the exposed copper wire is of the length 1mm and the wire is not bent or corroded
STEP 5 – Use a voltmeter to check the voltage consistency. If it shows the value of 24V then it means the wiring is just fine
STEP 6 – After examining the wire, insert it back into the connector
STEP 7 – Perform the same test on the remaining wires
STEP 8 – At last, turn ON the thermostat by attaching it to the related breakers

This will definitely solve your problem if the issue is within the wiring of your thermostat.


Another reason for no power to nest thermostat is the presence of clogged air filters. A proper air flow is very essential for the correct working of your HVAC system. If the air filters are clogged then the air flow will be disturbed causing damage to other components as well.

nest thermostat clogged air filters


To check the air filters of your system, you need to follow the following steps.

STEP 1 –The first step that should be taken by you is to locate the air filters. There are two possibilities for it; they could either be present behind a grate along the ceiling or inside your furnace
STEP 2 – After locating the filters, if you find them dirty or clogged then you need to make a replacement as soon as possible
STEP 3 – However, if you witness frozen cooling coils then give them some time to defrost before using them again

If you want to prevent such issues then it is important to make a replacement of air filters after almost 90 days

Nest thermostat not detecting wires could be due to clogged drain tubes or pan. The purpose of these tubes is to carry condensed water far from the HVAC system. If these drain tubes or pan is not present then the water could be backed up causing heat pump and AC to shut down. This shutting down is done to prevent a water overflow. If all this happens then the HVAC system will not send any power to your Nest thermostat which will automatically cause error E73.


If you want to resolve this issue, it is important to follow these steps properly.

STEP 1 – Make sure your HVAC system is powered OFF by turning off all the breakers
STEP 2 – The next step would be to locate the cooling coils. If you find them behind a sealed panel then consider taking professional help as this task demands high technical skills
STEP 3 – Once you have located the cooling coils, it is time to find the drain pan which can usually be found under the coils. Check if the pan is filled with water and if not then check whether the tubes are clogged up or not
STEP 4 – If you find water in the drain pan then it means there has been a clog/blockage within the drain tubes
STEP 5 – Take help from the manual or from online resources in order to know details about how to clean the clogged tubes


As you know that the hot weather conditions can cause your thermostat to work harder than usual. This extra effort causes the HVAC fuse to burn out which cuts the power flow from your HVAC system to your thermostat.

nest no power to RC wire FIxes


In order to troubleshoot this issue, you need to follow the following steps.

STEP 1 – Turn off the breakers and make sure your HVAC system is OFF
STEP 2 – Now look at the control board of your HVAC system and find the HVAC fuse
STEP 3 – Inspect the fuse to know whether it is damaged or not. You will find it discolored if it is burnt, in this case you will need to make a quick replacement
STEP 4 – Once replaced, make sure you made the right connections just like before


If you have implemented all the above mentioned steps and still you get RC wire no power issue then it is recommended that you contact the Nest support. Give them a detailed report of the steps which you have implemented so far. The issue might lie within your Nest thermostat so it is better to keep it checked quickly.

nest no power to RC wire


Q – What Does E73 Mean?
A – Error E73 indicates no power to RC wire issue. To get rid of it, it is recommended that you check the wiring of your thermostat, drain tubes and pans, HVAC fuse and air conditioner filters.

Q – Does Nest Work With RC Wire?
A – Yes, Nest works with RC wire. This wire goes into the Rh or Rc connector of your thermostat.

Q – Why Is My Nest Not Detecting RH Wire?
A – Nest not detecting RH wire could be due to power issue. Check and examine the wire that it is straight and not corroded.

Q – How To Replace A Burnt HVAC Fuse?
A – If you have a little bit of knowledge regarding the replacement then you can easily get the fuse replaced. However, if you find it difficult then it is better to call in some professional help.


If you want to solve the no power to RC wire issue then simply follow the above mentioned methods so you don’t have to face further inconveniences. If the mentioned methods don’t work out for you then it is better to call the Nest support.

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