nest thermostat not detecting rh wire

Having the issue where your Nest thermostat not detecting RH wire? Worry no more, because you have just discovered the solution.

In fact, there is more than one workaround that has proven to work by users having their Nest not detecting the RH wire.

If the Nest thermostat isn’t detecting the RH wire, there is a high possibility that there is a loose connection somewhere in your configuration. 

If that isn’t the case, make sure that the drainpipes are clear and check if the condensate pump is clogged with your HVAC.

If your issue is still there, check out the rest of the post as first we’re taking a look at all possibilities and then providing a solution for each of them.

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Why Is Nest Not Detecting RH Wire?

To make the troubleshooting easier for you, we figured it would be more appropriate to get familiar with the issue first.

This is why we’ve prepared a quick list of possible causes for you to check out before starting troubleshooting with our guidelines.

  1. Clogged/frozen drain line.
  2. The furnace switch might be off.
  3. Your RH wire is connected to the G terminal.
  4. Incompatible Nest Thermostat with AC
  5. Outdated/unsupported version of Nest Thermostat with AC.

If your problem is related to one of the above-described possibilities you’ll definitely get it fixed by the end of the post.

If however, the issue is related to a faulty hardware part you might have to spend some money for repair, so let’s find out!

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How To Fix Nest Thermostat Not Detecting RH Wire?

fix nest thermostat not detecting rh wire

Before performing any of the steps we will share with you below, it would be in your favor to check if everything is up and running in your configuration.

Take your time to perform the obvious preparation including a restart and if it does not help, you can start.

Method #1 Check For Loose Connection

The first and most general method that we are going to review is the wiring in your configuration. Many users report that after the re-establishment of their setup this error message appears.

This means that nothing is established correctly or some of the wirings aren’t working.

The best thing you can do to ensure that all of your cables work properly is to unplug them all and connect them consecutively.

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This way you will figure out if something isn’t working and determine which one of the cables is faulty, including the RH wire.

Method #2 Clean Out Drain Pipes

The next thing you have to check is your drain pipes. The way Nest works are if the drain pipes are blocked, they will automatically be prevented from working.

Then, the RH Wire error message will appear on the screen of your Nest.

To ensure the safety of your drain system, you have to check your drain pipes if something is blocking them.

For instance, during the winter seasons, the water your system is ejecting might be frozen, which will block your drain system.

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In conclusion, make sure to always maintain and keep your drain pipes clear. If there is an odor within the pipes, for example, your AC will start to bring a not-so-good smell of air inside your household.

Method #3 Check HVAC Float Switch

Your HVAC system will be delivered with a condensate overflow switch. This specific switch is located somewhere near the air handler and it is designed to prevent water overflowing in your house.

After checking for loose connection and the situation with your drain pipes, you should definitely take a look at your HVAC float switch.

You must make sure that it is turned and working. Otherwise, your Nest will display frequent error messages and let water inside of your household.

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To check if the switch is turned on, it should make a clicking sound after slight rattling. If it makes a sound, this means that the float switch is situated where it is supposed to be.

Method #4 Check HVAC Control Unit Fuse

The control unit fuse can be frequently blown away if there are power fluctuations and loose connections.

After establishing the conclusion that there is no problem with your wiring, the next thing you should check your system for is power fluctuations.

Note: This fuse is attached to the control unit within your HVAC and it is a tiny valve located on the right side of the HVAC.

We’ve prepared a quick list to check if your HVAC control is functionating.

  1. Disable the HAV system.
  2. Dismantle the fuse.
  3. Check the connection center for broken or flooded parts.
  4. If a u-shaped wire is interrupted by any means, the fuse is blown.
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Our best suggestion is to purchase a brand new HVAC control unit if this part is broken or flooded.

It is well-known that such parts are really difficult to mount, even if the process is performed by highly skilled technicians so if you aren’t confident, seek help.

Method #5 Charge Nest Via USB

If the power of your Nest was out for more than 12 hours and there aren’t any signs of it detecting the RH wire, you can try charging your device via USB.

Simply plug the thermostat into a device that has USB slots such as laptops/pc or a power outlet and charge it for a while.

If the display is still blank after a few hours, you have to charge the battery manually.

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The steps down below will explain to you how to charge the battery of your Nest thermostat using a USB type of connection.

  1. Dismantle the thermostat from its wall stand.
  2. You will see two connectors located at the back of the device.
  3. Locate the micro USB slot.
  4. Connect with a device that has USB slots.
  5. Let it lay for several hours to charge its battery fully.

Nest Thermostat Still Not Detecting RH Wire?

If nothing we’ve discussed above has aided your troubleshooting experience, it is perhaps time to pass this task to someone more skilled.

Do not hesitate to seek further assistance from manufacturers or local technicians that are experienced with Nest issues.

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If the problem is more complex, calling someone to help you out is the best thing you can do.

It is well-known that it could be a really hard task taking care of these issues. In that case, so don’t hesitate to get in touch with someone who can help.

On the other hand, if you’ve come up with the conclusion that this whole issue is your thermostat’s fault, you should consider a newer model of Nest.

Otherwise, we hope a firm reestablishment will be able to keep things going.

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Now that you know why the Nest thermostat isn’t detecting RH wire, you should be successful at troubleshooting the issue.

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We’ve managed to gather enough information to make your troubleshooting experience as easy as possible, so make sure to apply our methods correctly for the best results.

You can find more helpful guides including Nest thermostat on our technical blog that can offer you a handful of helpful and interactable posts.