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HVAC Guru
HVAC Guru, HVAC TECH
Category: HVAC
Satisfied Customers: 14029
Experience:  15yrs in the HVAC industry with certificates and degrees.
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My nest was working fine. When we woke up today, the AC was

Customer Question

Hi Pearl, my nest was working fine. When we woke up today, the AC was off and we received the following message on the nest: No power to Rh wire detected.
JA: I'll do all I can to help. How long have you been dealing with this?
Customer: since this morning. it is already 90 degrees here
JA: Do you plan on doing the work yourself?
Customer: yes
JA: Anything else we should know to help you best?
Customer: that is all the facts
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the HVAC Technician about your situation and then connect you two.
Submitted: 5 months ago.
Category: HVAC
Expert:  HVAC Guru replied 5 months ago.

Hello and thanks for using this service, if you have been waiting do not worry or get upset. I am HVAC Guru an extremely experienced tech on the site and I try to get to as many customers as I can. I just picked up your question now. NOTE it takes time for me to type research and add links so please wait for me to respond back I can only do this so fast. Secondly I am not paid anything until you rate my service good using the STAR RATING LINK at the top of your page, the money is paid to the site not me directly.

Answer:

That means that you have lost your low voltage supply to the unit you need to check from R to C at the thermostat wires for 24 volts AC. If you do not have that then.....

What likely happened is the low voltage fuse in the furnace or airhandler blew. There typically is a SLOT STYLE 3-5AMP FUSE on the board itself inside the furnace/airhandler like this.

CLICK HERE

If that is burned out all power to the thermostat will be lost. 95% of all units use some sort of SLOT FUSE or inline BUS STYLE FUSE to protect the low voltage circuit. You need to find that and change it out. If you just bump two wires together you could have just popped it without even knowing it. Now if for some reason your unit does not use a fuse often the board will be damaged due to the short. You would need to confirm you have 24 volts to the board inside the furnace/airhandler with a volt meter to make sure though.

Note if you have a condensate pump check the float and make sure the pump is not full of water...as that could cut low voltage power to the unit as well if the pump is not working and full of water.

All I ask is please use the Star Rating Link at the top of your page before leaving, that is the only way I am paid anything through the site and that will also get you a DIRECT LINK emailed to you to get back to me!.....tips are greatly appreciated so thank you very much for using this service. If you have any other questions just post back to me here anytime!