Fan Runs Constantly

[hummingbird]

After working well for about 2 months, the fan started running continuously. The only way to stop it is to go up in the attic and manually turn off the air handler.

We had a repair person out who said the air handler is fine. He added the C wire which fixed the problem for about 2 days.

It's possible the relay switch on the air handler needs replacing, but we would like to fully trouble-shoot Nest issues before calling out for another repair visit.

Thank you.

[Houptee]

Remove the G wire at nest and see if it continues to run fan all the time. 

If yes it is most likely the relay in the air handler.

You can replace it yourself as long as it is not built into the control board. 

Take a picture of the air handler connections and the relay if you know what it looks like. 

[hummingbird]

Thanks Houptee for the quick reply.

Earlier today I disconnected the whole device and the fan continued to run.

[Houptee]

If fan runs with no thermostat connected, and no wires touching, then you most likely need the fan relay inside the unit replaced.

But without seeing pics of the inside of the unit and the brand with model number I cannot determine what to tell you other than post some more pics.

[Jhonleanmel]

Hey folks, 

Thanks again for helping here, @Houptee. 
@hummingbird, I hope you've got the answer you're looking for. If you're still in need of any assistance, feel free to let us know. 

Best,
Mel

[hummingbird]

Thanks - we're in a holding pattern for now. The unit is difficult to access so we're going to have a pro in to take a look at it. We'll follow up to let you know what they tell us so if others are having similar issues it will be documented here. Thanks!

[Jhonleanmel]

Hi hummingbird,

Thanks for letting us know. Take your time, I'll be waiting for your update.

Regards,
Mel

[markemory1]

Any solution yet? I have the same issue with fan not turning off. Even with thermostat disconnected, but if I reinstall the old thermostat the fan works fine.

[hummingbird]

Hello!

The service technician we had out to look at the issue confirmed Hooptee's suspicion that the fan relay needs to be replaced. In our unit, that's built into the control panel. A control panel has been ordered and once it's installed I'll provide a hopefully final update.

Here's a summary for those who are trouble-shooting:

Nest Learning Thermostat installed and worked great for about 2 months until the fan ran continuously.

The C wire hadn't been connected so we connected it and at first thought the problem was resolved.

After a couple days, the fan continued to run continuously.

We removed the Nest thermostat and the fan still continued running.

The only way to turn off the fan was to disconnect power to the air handler.

The open question is whether the relay fan was nearing its end of life and it was just a coincidence it failed shortly after the Nest was installed without the C-wire or whether the constant running of the fan while there was no C-wire installed contributed to the failure.

Thank you all for your help, suggestions and follow-up. This is a valuable discussion board.

[Jeff]

Thanks for the detailed update, hummingbird. It sounds like you were able to get it all sorted out. We'll keep an eye on things for a couple of days to make sure all is well, but if anything comes up in the coming days, definitely let us know. Also, if you have any other needs, feel free to bring those up here.

Thanks,

Jeff

[EmersonB]

Hi everyone,

@hummingbird I'm dropping by to ensure that everything is covered here. I hope that sheds some light on the issue. If you have other questions and concerns, feel free to let me know.

I appreciate the help, @Houptee, @mel and @Jeff.

Regards,
Emerson

[hummingbird]

Hi Emerson,

We're in holding mode at the moment.

A new control panel has been ordered so we're waiting for it to arrive.

I'll post a follow-up update once that's completed. 

I greatly appreciate the help from the community. 

We were scrambling in crisis mode when I originally posted and @Houptee replied within hours - and I think it was on a weekend. His troubleshooting advice was spot-on and greatly appreciated.

The follow up from Community Specialists is also appreciated.

Thank you!

Hummingbird

[EmersonB]

Hello hummingbird,

Thanks for letting us know. Take your time, I'll be waiting for your update.

Best,
Emerson

[EmersonB]

Hi hummingbird,

How's it going with your fan? Have you received your control panel order?

Keep us posted.

Thanks,
Emerson

[hummingbird]

Hello! Thanks for checking in about our progress.

If all goes according to plan, the new panel will be installed Monday.

Thanks - Hummingbird

[EmersonB]

Hey hummingbird,

Thanks for getting back to us. Sounds like a plan. Keep us posted.

Best,
Emerson

[Markjosephp]

Hello hummingbird,

I wanted to follow up and see if you are still in need of any help. Is your new control panel already installed? How's it going so far?

Best regards,

Mark

[hummingbird]

Hello!

The new control panel was installed yesterday and now the fan turns on/off correctly.

For those who are troubleshooting - the air handler relay switch was the problem. 

On our unit, the relay switch is embedded in the control panel, so the control panel was replaced.

Thanks to @Houptee and the community specialists who have been providing support.

All the best to you all - Hummingbird

[Markjosephp]

Hi hummingbird,

That sounds great! Thanks for getting back and letting us know how installing a new control panel was able to resolve your concern. Big help!

So I'm going to lock this thread in 24 hours unless you have other questions or concerns.

Best regards,

Mark

[markemory1]

I still have not been helped.

[Markjosephp]

Hi markemory1,

Thanks for getting back to us, and I'm sorry if you're still having the issue. Let's sort this out.

To isolate, could you please tell us what type of Nest thermostat you have? Here's your reference to tell which you have. Were you able to follow the steps being shared on this thread? Did that help?

I'll look forward for your response.

Best regards,

Mark

[markemory1]

"Nest thermostat"

Yes I followed the steps in this thread, it did not help.

[Markjosephp]

Hi markemory1,

Thanks for trying all the steps shared in this thread.

To better look into this, please fill out this form so we can check for more options and let me know once you're done.

Best regards,

Mark

[markemory1]

Form is done

[hummingbird]

Hello Markemory1 - You mentioned in a note to me that when you replaced the Nest thermostat with the previous thermostat the "fan running all the time" issue resolved itself. It only ran when it was supposed to run.

I'm not an expert in HVAC like some on this thread, but I'm not a bad troubleshooter in general. That would lead me to believe your issue is more likely with the Nest than the heating/cooling unit.

I can't speak from personal experience as when we were trouble-shooting we didn't try putting the original thermostat back on. I can tell you that in our case we believe it was the relay switch on the air handler. We had that replaced and now the fan no longer runs unless the unit it heating or cooling.

[markemory1]

Yeah when I put the original back on the issue goes away. This is the 2nd nest thermostat I’ve tried. Unless they sent me 2 bad ones in a row, I figure it has to be some kind of setting issue.

[hummingbird]

From reading other responses on this board, it could well be a wiring issue.

At first our Nest didn't have the "C" wire connected and the fan ran all the time.

We connected the "C" wire and it fixed our issue for a short time.

For many who post here, connecting the "C" wire was the permanent fix.

Is your "C" wire connected?

[Markjosephp]

Hi everyone,

Thanks for sharing your experience with your Nest thermostat and how you were able to fix it, @hummingbird. Big help!

We got your form, @markemory1. Thanks for filling it out. Keep your lines open as our team will reach out to you via email anytime soon. Also, please continue the conversation there as this thread will be locked after 24 hours.

Best regards,

Mark

[markemory1]

Yeah my C wire is good.

[Markjosephp]

Hi markemory1,

Thank you for your patience with us. We've created a case for you. Your issue has been escalated to our upper support team. Be on the lookout for an email from us in your inbox soon, as we will be locking this thread in 24 hours.

Best regards,

Mark