topic Re: "No power to Rc wire detected" E73. in Nest Thermostats

"No power to Rc wire detected" E73.

CDF1 — Wed, 13 Oct 2021 20:30:57 GMT

Doing research here this post has occurred several times but are all closed. The answers are not fixing the problem. This has happened daily for me for several days now. Works fine and then error message and system turns off the AC. My fix has been wiggle the wire a little at the connector and turn off the AC unit breaker. It works again for a bit and then nothing. I have used a lot of Next thermostats and this is the first of this problem. The thermostat has been installed on a new unit since March of this year. Nothing has changed. Please help.

Re: "No power to Rc wire detected" E73.

TerryL — Mon, 18 Oct 2021 20:50:36 GMT

I'm having the same issue. My new heat pump and Nest Thermostat was installed a year ago. A few days ago I got the same error message. When I turn the heat pump breaker off for a while the error message goes away and AC runs for about 10 mins then the error message is back. Have you found and solutions?

Re: "No power to Rc wire detected" E73.

CDF1 — Mon, 18 Oct 2021 21:38:55 GMT

I haven't found a solution nor has anyone responded. Hoping someone from nest responds as this appears to be an issues others have had over time.

Re: "No power to Rc wire detected" E73.

mvyoung — Mon, 08 Nov 2021 12:58:45 GMT

I am having a similar error message appear. I can’t figure it out! Did you ever hear back on a solution

Thanks

Mike

Re: "No power to Rc wire detected" E73.

CDF1 — Mon, 08 Nov 2021 13:53:05 GMT

I did not. I just kept reconnecting this wire and it has ultimately stopped for now.

Re: "No power to Rc wire detected" E73.

TerryL — Tue, 09 Nov 2021 21:14:20 GMT

I looked up the error code in Google Nest online and it was suggested to check the drain pan, the filter and the fuse. Fuse was good, drain pan was good, so we changed the filter. Now it works and no error message. No sure if this was a coincidence or if I hit the spot.

Re: "No power to Rc wire detected" E73.

GarrettDS — Tue, 09 Nov 2021 21:44:57 GMT

Hey there,
Sorry for the late response, but I wanted to drop in here to help.

I understand that these issues can be confusing but I definitely wanted to stop by and see how I could help.

Just wanted to double check to see if you were still needing help on this? If so, what troubleshooting steps have you tried?

Please let me know.

Best regards,
Garrett DS

Re: "No power to Rc wire detected" E73.

mvyoung — Wed, 10 Nov 2021 19:39:37 GMT

Thanks for the reply CDF1. I'm glad it stopped for ya. Still working on it here!

Mike

Re: "No power to Rc wire detected" E73.

mvyoung — Wed, 10 Nov 2021 19:43:12 GMT

Hi TerryL,

Thanks for the reply! I appreciate it. All that I really have done is turn the circuit breakers on and off to both the furnace and the blowers for the AC unit. An electrician told me that the Fc wire is really indicative of the AC blowers. In addition, I have removed the copper wire that enters where Fc is labelled. The wire seems to be similar to the others. Other than that I am at a loss!

Thanks

Mike

Re: "No power to Rc wire detected" E73.

mvyoung — Wed, 10 Nov 2021 19:46:31 GMT

Sorry TerryL. With regard to the other functional things, I will check the drain pan, the filter and the fuse. May I ask, when you say check the fuse, is that the same thing as the circuit breaker or are you referring to a separate fuse closer to the actual HVAC system - be it the furnace or the AC blowers?

Re: "No power to Rc wire detected" E73.

mvyoung — Wed, 10 Nov 2021 19:49:12 GMT

Hi Garrett DS,

Thanks for the reply! I very much appreciate it.

I have:

1. Turned the circuit breakers on and off to the heating and cooling units

2. Inspected the copper wire going in an out of the Fc space on the thermostat

That's about my limit

Another suggestion from a previous member was to inspect the drain pan, the filters and the fuse.

Thanks

Mike

Re: "No power to Rc wire detected" E73.

TerryL — Sun, 14 Nov 2021 05:40:10 GMT

There is a fuse in your HVAC unit to heat pump. Check to see if it hasn’t burnt out. Not knowing where mine was, I called my unit’s installers and and they did a courtesy drop by to check the fuse and drain pan. If that is not an option for you, check your unit’s manual for access and location of both the fuse and drain pan.

Re: "No power to Rc wire detected" E73.

Tridge — Mon, 25 Apr 2022 21:54:06 GMT

Having the same issue. I got an error mesh saying no power to RC line. My system has shut down. I charged the thermostat manually and it come on when plugged in, the says it has to shut down.

Re: "No power to Rc wire detected" E73.

tgdtouchton — Wed, 04 May 2022 18:29:54 GMT

I know I'm late to the game here, but here's something I found while installing a couple of Nest thermostats today. The fuse in question is for the low voltage circuit that supplies roughly 24VAC. On my system the fuse is on a small circuit board inside the HVAC unit. It's not installed in a normal fuse holder, it's installed using two female spade terminals. In my situation the fuse was corrected inserted in one of the terminals but was not in the other. It was laying on the terminal which allowed it to make an intermittent connection. With temperature changes (this is in my attic) and vibration the connection between the fuse and the circuit board was not reliable. If the fuse is blown you will have a constant E73 error. There is no low voltage. But, if you're still having intermittent issues, this is something to look into.

Re: "No power to Rc wire detected" E73.

GB4 — Thu, 02 Jun 2022 13:02:24 GMT

I had that issue and could not get the system to turn on. Found out it was the AC float switch. If it gets water in it that will shut off the power to the thermostat

Re: "No power to Rc wire detected" E73.

GB4 — Thu, 02 Jun 2022 13:06:09 GMT

And I'd add to that the float switch that shuts off the power to the thermostat. I had the same no power until adjusting and emptying the float switch.

Re: "No power to Rc wire detected" E73.

Arivero — Tue, 14 Jun 2022 15:36:00 GMT

If you remove the face cover and the wire is OK the usual problem is the float switch. The float switch is in your unit and when there’s back up from clogging of water,floods up of water it Causes the floater to rise and cut off the power.

you need to unclog the unit. Pouring Clorox (NOT POOL CHLORINE) should solve the problem

Re: "No power to Rc wire detected" E73.

GB4 — Tue, 14 Jun 2022 16:31:46 GMT

exactly what the issue was with my thermostat. I flushed the line and a bunch of crap flowed out. Issue solved.

Re: "No power to Rc wire detected" E73.

QueenOfCars — Thu, 23 Jun 2022 01:23:30 GMT

I have the Nest 3rd Gen eLearning and got the e73 error code. Needless to say, I was hot and bothered. 😂 This fixed my problem. It was just a matter of charging it via a USB cable just like charging a cell phone. https://support.google.com/googlenest/answer/9245516?hl=en

Re: "No power to Rc wire detected" E73.

Della — Wed, 06 Jul 2022 14:17:18 GMT

What did you do to the float switch to fix it?