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"No power to Rc wire detected" E73.

CDF1
Community Member

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.

67 REPLIES 67

TerryL
Community Member

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?

BrennSon
Community Member

I had this same issue. Also anytime there was a power outage, when power came back, the nest was showing e73. I’d have to go turn off/on the main furnace switch and then all was fine. After going back and forth with google support, I convinced them to send me a new wiring plate for the thermostat (the little piece you connect all the wires into) cause I figured maybe the one I had was faulty. Sure enough - that fixed it. I installed the new wiring plate and have never had the issue since!!!

CDF1
Community Member

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.

Tridge
Community Member

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.

GB4
Community Member

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  

Della
Community Member

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

GB4
Community Member

I had to clean out the drain line for the air conditioner. Once the water drained it left the float switch and AC came on

KBA1
Community Member

Yes,  it was the float switch!!!  The main drain line that drains the AC from the unit to outside the house was clogged baking up water in the drain causing the float switch to activate. OnceI  cleaned out the drain line all is working fine and the Nest Code "E73 wiring report" cleared on my Nest 3rd Gen Learning thermostat. 

Demar
Community Member

Thank you!!  This turned out to be my issue with the E73 wiring error code.  I pulled off the cap to the drain pipe and some water overflowed out of it and it immediately restarted for a short time before quickly filling up again.  For anyone with no clue about this stuff like myself--after watching a few youtube videos about unclogging the drainage line, I used a garden hose to blast water down the pipe to clear the clog.  If you have an air compressor, you can use that too (probably the better option); or a shop vac to suck out the clog from the outside end.  My unit had routine maintenance 6 months ago so it's due, and living in a very warm climate we use it year round and it gets gunked up pretty quickly. 

Kash13
Community Member

Brother you’re a god send thank you! I have a sick 3 year old and 3 month old and this was exactly my problem when mine went out. 

KBA1
Community Member

After figuring that out it what a fix to to entire unit shutting down😂. Glad it worked for you !!!

GB4
Community Member

Glad that you got it up and running quickly! I couldn’t find anything out on line at the time when mine went out about the no power message so thought I’d post (I rarely post comments).  I had to track it down (after being off for 8 hours) with a friend to find the issue!

KBA1
Community Member

Yes,  it was the float switch!!!  The main drain line that drains the AC from the unit to outside the house was clogged baking up water in the drain causing the float switch to activate. OnceI  cleaned out the drain line all is working fine and the Nest Code "E73 wiring report" cleared on my Nest 3rd Gen Learning thermostat. 

Vichandy
Community Member

Same does to me

i keep draining the tray and keep filling in the tray and float switch turns of the power.

I still don’t know the issue 

jean54
Community Member

Having the same issue , message E73.  Where is the float switch?

GB4
Community Member

It's usually next to the drain pan which is located under the AC air handler. If the pan under the unit fills with water (instead of draining) it raises the 'float' and cuts electric off to the thermostat which stops the unit from running and overflowing the pan.  

Nandor
Community Member

I think you refer to the sensor close by the drain pipe (which should be accessible from outside) that drops the moisture down to the pump to push it outside.  The final solution for your problem will definitely depend on the AC type and specifications and available features (tonnage, dehumidifier, air filter type, stages, heat pump, etc., you name it). I changed the drain pipe to copper (plastic clogs up with bacteria), take out the float switch completely (so can not be flooded), replaced the Nest battery and Nest itself (there is an option for it from Google) put it offline, and killed its smart features and its schedule/learning capability, trashed the AC fancy air filter system (works by potentially zapping bacteria/viruses), but not actually cleaning the air. You can also try to replace the baseplate (ask Google for a replacement). Currently, my Nest runs on a complete manual setting, with minimal problems.

 

I think Google made a well-designed Nest that is not compatible with many AC features and wants the customer to work out all the problems with it. Its smart capabilities are garbage, and down the road, you will recognize how much smart stuff you really need and where.

Airdog
Community Member

I also have same issue - it is not the float line - system installed last March - has worked fine until today - wondering if the software update has anything to do with this??? All other steps checked!

GB4
Community Member

I haven’t had any issues with the software updates. Did you reboot by disconnecting it from the base and reconnecting? Another issue I just found out which has the same error message is low Freon and the compressor turning power off to the thermostat. 

CGar
Community Member

What software update? I’m having the same problem

QueenOfCars
Community Member

Both times I got this message I ended up calling my HVAC maintenance company and both times all it took was a shop vac to the outside drain. If it gets clogged the system will show this error. The drain should always be dripping and even if it is it could still be clogged. Good luck!

SAHMof2
Community Member

Same! New unit, pan was dry. AC did not work for about 30 hours and then randomly, out of the blue started working. We took the nest off and charged with a USB......have never done it before in the 8 years we have had it. Not sure if that was that problem.

BrennSon
Community Member

I had this same issue. Also anytime there was a power outage, when power came back, the nest was showing e73. I’d have to go turn off/on the main furnace switch and then all was fine. After going back and forth with google support, I convinced them to send me a new wiring plate for the thermostat (the little piece you connect all the wires into) cause I figured maybe the one I had was faulty. Sure enough - that fixed it. I installed the new wiring plate and have never had the issue since!!!

Toddykc
Community Member

No response. Crap product. Shocker 

mvyoung
Community Member

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

 

Thanks 

Mike 

CDF1
Community Member

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

GarrettDS
Community Specialist
Community Specialist

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
 

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

 

Swd
Community Member

I am having trouble and not related to float switch. 

Jmf4cj
Community Member

Same here. I have an AC specialist installing my Google nest and he has tried everything. He thinks it’s a defective Nest and should be replaced 

mvyoung
Community Member

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

Mike

Arivero
Community Member

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 

GB4
Community Member

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

 

KBA1
Community Member

Yes,  it was the float switch!!!  The main drain line that drains the AC from the unit to outside the house was clogged backing up water in the drain causing the float switch to activate. Once I cleaned out the drain line all is working fine and the Nest Code "E73 wiring report" cleared on my Nest 3rd Gen Learning thermostat. 

TerryL
Community Member

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. 

mvyoung
Community Member

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

mvyoung
Community Member

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?

TerryL
Community Member

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. 

KBA1
Community Member

Yes,  it was the float switch!!!  The main drain line that drains the AC from the unit to outside the house was clogged backing up water in the drain causing the float switch to activate. Once I cleaned out the drain line all is working fine and the Nest Code "E73 wiring report" cleared on my Nest 3rd Gen Learning thermostat