Nest Thermostat wiring error

[RMcC]

I’ve had my Nest Thermostat for many years and it has worked perfectly. All of a sudden this morning it is giving me a wiring error and I haven’t been anywhere near the thing. Was there an update or something that I missed? I would’ve broken this?

[CoolingWizard]

Perhaps you HVAC system has failed ? What is the specific error number you received?

AC Cooling Wizard

[RMcC]

E 103 just found this trail. 

https://www.googlenestcommunity.com/t5/Nest-Thermostats/E103-yet-again-No-changes-to-wiring-and-I-m-...

[Markjosephp]

Hello folks,

I wanted to stop by and see how I could help.

Thanks for lending a hand, @CoolingWizard.

@RMcC, your thermostat's internal breakers will activate to protect the thermostat base plate and other system components from damage if they detect an overcurrent, which occurs when the electrical current on the thermostat wires connected to the Nest Thermostat spikes repeatedly.

Could you please check its power readings with and without the Y1 wire? Also, remove the common wire, if there is one. Note: Turn off the power from your HVAC system at the breaker box before touching the wire.

Let me know how it goes.

Regards,
Mark

[RMcC]

AC guy came out here are his notes, I also had to purchase a new Nest Thermostat 😞 

his visit was for no AC, on arrived turned on unit at nest thermostat and nothing would happen. I then jumped out thermostat and 3 amp fuse tripped in furnace. I replaced fuse, disconnected contactor at condenser and tried again, now fuse did not trip. Placed wires back on contactor and tripped again. When wires were connected to nest sub- base it was bleeding Voltage (25v) to Y, NEST is also shorted out. With both wires disconnected from thermostat, I still have 6 v of Voltage bleed. Advised to homeowner he may need new wires ran if this happens again due to the Voltage bleed . Customer approved replacement of contactor and capacitor today, and would like to change the thermostat him self. I let him know a thermostat should be professionally installed and could damage the system if not properly installed. I tested unit by bypassing thermostat, and it is working properly at this time. Took off my jumpers and shut power off to furnace. Customer is aware of this.

[CoolingWizard]

The only way a Nest can create a short to ground is if the C terminal was cross connected to R or an active Y terminal.  The failure was the contactor and the contactor coil shorted out while energized. That is where the short initialized.  This short more than likely damaged the Nest sub base.  That is 40 Volt Amp transformer and that dead short went from Y there the base to R and then to Transformer.  What model Nest thermostat do you have? 

AC Cooling Wizard

[RMcC]

The model number I had was A00131. It is a learning model that I have had for a few years with no issues. 

I purchased the same type and it is working fine so far. All in over $1000 I didn't expect to pay for repairs but that is just life I guess 🙂 

[CoolingWizard]

I am so sorry to hear about the expenses.  The capacitor cost the service company about $50 and the transformer about the $28.00 the rest was labor and profit.  

[RMcC]

Where the f were you yesterday! lol 

[CoolingWizard]

I work in the lower desert area of California.  Sorry, I not able to be there. 

AC Cooling Wizard

[Markjosephp]

Hi everyone,

I'm dropping by to ensure that everything is covered here.

Thanks for looking into this, @CoolingWizard.

@RMcC, how's it going? I'd like to check if you were able to get your Nest Thermostat working. Feel free to reach out again if you still need help.

Best regards,
Mark

[RMcC]

Thanks for checking in Mark! I purchased a new Nest and it is working. The New Jersey weather has kept it busy with temperatures fluctuating from 40° to 80° 😳 So heat and cooling are working as expected! Thanks again😊

[Markjosephp]

Hi there,

Sounds great! I appreciate you keeping up with another Nest Thermostat, and I'm glad to hear it's back on track. It looks like we can consider this one complete, so I will lock the thread within 24 hours unless I can help out with anything else.

Regards,
Mark