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Nest Thermostat No Power To Rh Wire: How to Fix? (2024)

nest no power to rh wire

I took some days off from work so that I could rest and enjoy some β€œMe” time. I had no such outdoor plans because the temperature of my city was very hot. So I decided to stay home, but then there came a twist which destroyed all my plans.

My AC stopped working! What an unfortunate incident. I tried to calm myself because recently I dealt with two other issues as well; one was when my thermostat was not providing the sufficient heat and secondly when my thermostat needed a C-wire addition.

I wasn’t ready to afford any further complications. I was worried that now I will have to get my AC serviced but thanks to my Nest thermostat which told me about the issue. Nest thermostats are good in this way that they tell you about the error along with its relevant number. In my case, I got to see error E74 which meant no power to Rh wire detected.

Nest No Power To Rh Wire Issue Can Be Fixed By Adjusting The Relevant Connections. Inspect If There Are Any Lose Connections, If Found Them Fix Them As Soon As Possible. If There Are No Loose Connections Then It Is Better To Check The Drain Pipes To Know Whether They Are Clogged Or Not. If This Is The Issue Then Get Those Pipes And Condensate Pump Cleaned.


I didn’t want to call the professional help so I decided to do this task myself. I looked for online solutions and at last I found two of them. One was to fix the loose connections while the other fix was to check the condensate pump and drain pipes for clogging. However, there are other reasons as well but the most common ones are these two.


In order to troubleshoot your system, it is important to know all the relevant ways to get the job done. Even if you don’t know them, we are here to assist you.


There is a float switch which comes with your HVAC system. This switch is located just near the Air Handler Unit so you won’t have to face difficulty while finding it. The main purpose of this switch is to prevent your home from overflowing with water. If the pipes are clogged or the water is not flowing properly then you will notice that the switch will show a disconnection. It means no power will be provided to the AC.


The floating mechanism will disconnect the switch as soon as it reaches the top. This top position is reached due to the access to water. It means you have to check the float switch working manually. To check this we have a way which you can follow in order to avoid multiple inconveniences.


Nest no power to Rh wire could occur due to the disconnection shown by float switch. To ensure the proper working of this switch, rattle it. If you hear a clicking sound then it means the switch is working just fine.

However, if you don’t hear such a sound then it means the switch has reached the top and has access to the water. To get rid of this issue, clean the drainage pipes of your system and move the float to the bottom by yourself. Wait for some time and then restart your thermostat.


The error indicates that no power to Rh wire nest is provided. For this, your first step should be to check the Rh wire connection to your thermostat. There is a high possibility that the Rh wire connection is loose and sufficient power is not provided to the system.


Well, the fix for this is very easy, you just need to follow some steps so that you can get the work done. You will see β€œTech Info Diagram” option available on the main error page. Tap on it to open the wire diagram of your thermostat.

This option will highlight all the loose connections in red. It means the wires which are not properly connected will appear in red color. If your Rh wire is also red then what you need to do is remove the display and insert the wire properly. Make sure it is tightly inserted so it doesn’t experience any lose connection.


Nest Rh wire no power could be an indication that your HVAC contactor relay needs a replacement. There is no obvious reason for the malfunctioning of HVAC contactor relay. It usually starts showing abnormal behavior due to aging. It might cause sparks and could also blow out the fuse from the control unit.


If you face this similar situation then all you need to do is replace the contactor relay. If you want the replacement then it is highly advised that you call for the professional help. Doing this process on your own might be risky.

In some cases, the fuse needs to get replaced as well along with the contactor relay. The model of the relay depends upon the capacity and model of your HVAC system so take care of this fact as well.


Your HVAC system also has a fuse attached to its control unit. If this fuse is blown then Rh wire no power issue could occur. The fuse gets blown away due to the loose connections or power malfunctioning. To check whether the fuse is working fine or not you will have to follow the below mentioned steps.


STEP 1 – Make sure your HVAC system is turned OFF

STEP 2 – Now carefully remove the fuse

STEP 3 – See through the transparent casing of the fuse whether the center connection is broken or not

STEP 4 – If the u-shaped wire in white color is broken then it means the fuse is blown

It is important that you buy the same fuse model which you were using before. Also take care of the fuse color because it is meant for current rating, buy the fuse in the exact same color as before.


If there has been a power outage in your city and there was no power for more than 12 hours then the battery of your thermostat must be drained. The thermostat will start charging itself once the power comes back in. You will see a blinking light which indicates that the thermostat is charging.

But if that light stays for more than the required hours then you will have to charge the internal battery of your thermostat manually using a USB. For this, follow the below mentioned steps.


STEP 1 – Look at the back of your thermostat by removing it from the wall plate

STEP 2 – You will see two connectors, one of them will be a USB connector

STEP 3 – Connect it with a compatible charging cord and leave it for some time

STEP 4 – After a few hours, the display will reboot


No power to Rh wire nest could be due to the clogged drain pipes. If your system has clogged pipes then you don’t need to worry as this issue can be solved within no time. Just take your vacuum cleaner and start the cleaning.

For this, you don’t have to call in for the professional help. Make sure that you clean the drain pipes of your system regularly so they don’t cause damage to other components. If this happens then you will have to pay a lot of money to get the issue resolved.


However, if you want to use some extra help then you can always call the professional help. But if you cannot afford it then doing this process by yourself would be the best available option so far.


Thermostat Rh wire is a very important component especially when you want to use your AC mode. If this becomes faulty or there is no power provided to it, then it can cause a lot of trouble for you. It is better to try out every trouble shooting method because you never know which one might turn out the best for you.


Q – Why Is There No Power To My Rh Wire?
A – If you see that your AC is not working and power is not provided to your Rh wire then the reason might be the float switch. The float switch must have reached the top position due to the access to water. This switch prevents your AC from working if there is too much water present in the pan.

Q – Why Is My Nest Not Detecting Rh Wire?
A – Rh wire of your system might not get detected due to loose connections.

Q – When Does Nest Say No Power To Rh Wire?
A – Nest says no power to Rh wire when the connections are loose or when the drain pipes of your system have been clogged.

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