No Power Rh or Rc with E73 Error ode

[wawdallas]

Dog munched on wiring outside for thermostat control to AC Unit. Repaired and replaced fuse and Nest Thermostat is giving me an E73 Error code for no power to Rh. Moved to Rc and the same thing. Put old manual thermostat and it worked fine. swapped these out three more times and the Honeywell original thermostat works like a champ. Nest is stuck on the E73 and will not get past it.

Is this a bad puck or wiring plate or?

Y, G, W, C, Rh is what is used. We have had it working for a couple of years with no issues until now due to the dog.

[bluenow]

Many thermostat runs on battery and do not need C wire to function . But Nest Thermostat designed to use the wall wires to charge internal chargeable battery , and it detects the wire insertion to the base . In your case , if you have the C wire insert/connect onto the base but does not connect to your AC/furnace well , the  Nest Thermostat  will not be functional well . 

1. try to find the control wire on AC/furnace and make sure the C wire was connected to control board well .

2. if you can't do the 1 properly , try to remove the C wire from the base of Nest Thermostat , then check the nest if function well . Of course this will make Nest only charging in steal mode , and may cause low battery in long run , so it would be only for temporary test .

[wawdallas]

yes C (common) from Nest goes to the motherboard (C) and down to the contactor on the AC Unit.

Yellow (Y) does the same on the opposite side of the contactor.

G, W and Rh go to corresponding points on the motherboard.

The puck is not charging as you stated. I charge it per USB cable and reconnect. I still get the no power to Rh.

Any ideas appreciated.

[bluenow]

The Rh supposed to be the control to heat , so if it does connect well , the other thermostat wouldn't work either .  That is why I suspect the C wire connection on the HVAC side wrong .

As I said , without C wire the Nest Thermostat still barely work , so do the test , use USB fully charge the Nest , remove C wire from the base , put Nest back on to run on 4 wire configuration , see if it start to work . If this works , that means a problem on C wire connection. 

Another thing is , make sure all the wires inserted into Nest base are well conduct , you may want to scrape the copper surface to make sure well connection and conduction .  

[wawdallas]

Still no joy. Shows only Y, G, W and Rh is Red for no power still with C wire out.

as I said, the old Honeywell works like a champ so I am thinking something was fried on the Nest puck or even the wire board.

same everything as before inside. Also as I said the Nest doesn’t seem to hold any charge any more. Charged it all day and hooked it up to test it and less than 5 min it’s dead.

[bluenow]

That sounds your Nest be somethings wrong . It last only 5 minutes after fully charged by USB , appears to be either battery failed or other components consume exceeding current . 

However there is one thing still be puzzle to me , if an other thermostat on the terminal can work well the heater , that sounds Rh wire OK . Why Nest complain Rh no power ? Make sure the Rh has good conduction to the base of Nest , may scratch help ?

One of my 3rd gen Nest Thermostat appears WIFI failed suddenly , since I have 2 of the exact same type Nest Thermostat , I was able to do many test to swap and compare , surely to decide the problem is on Nest .

[JonP]

Hi. I got the Nest thermostat today, and I’m having the exact same issue. The old one works. Nest gives me same message as you. Were you able to fix it? Thank you !

[wawdallas]

Nope, figured the thermostat is bad. Wish I had a new one to see if it was the problem 100%. 

[AirBOB]

no dog here, a sacrificial mouse screwed up the wiring outside. I am getting the same message and am operating manually by jumping the y and r at the furnace. Is there a definitive way to tell if the thermostat was damaged? And does anyone from Google respond here, or are we on our own??