Nest e learning thermostat error 160 in morning-winter

[kc1005]

Our nest started giving an error code 160 (Y wire for cooling/ac unit) a couple of weeks ago. It ONLY shows when the heat first turns on after being down lower at night. We keep the temp at 64 at night, 67 in the morning. The error code shows after the furnace has been running but is not yet to 67 (usually at 66). It does NOT do this at any other time of the day when the heat comes on. Obviously central air is NOT on, nor should it be. Wiring at thermostat has been checked, as well as wiring to outside central air unit. Any other thoughts? Could the thermostat be "old" & need to be replaced? Can the Y wire be removed & the furnace/ac still function? Thanks

[CoolingWizard]

@kc1005 ,

there is normally a letter that proceeds the error code. So was this an E160?

AC Cooling Wizard

[kc1005]

Yes, E160 (Y wire)

[ByronP]

Hi kc1005,

Thank you for reaching out to the community. I’m sorry that your Nest Thermostat E shows an error message E160 when turning on the heating in the morning. I understand how frustrating this can be. I appreciate the help @CoolingWizard. I’m here to help.

Before I begin. I just need to ask a few questions for further assistance:

• What troubleshooting steps have you done so far?

• When did cooling last work?

• What type of system do you have? (Heat pump or conventional type)

• Have you set up a temperature schedule for your thermostat?

Please keep me posted. I’ll look forward to your response.

Regards,

Byron

[kc1005]

Checked the connections at the thermostat, furnace & wires to central a/c unit.

Cooling last worked in September (when it was hot)

Conventional heating system

Yes, we have a heating schedule set up

FYI, it does it every single morning. Starts, gets up above the current temperature, gives the error & shuts off. Immediately turns back on & heats to the temperature it is set for

Thanks for your thoughts

[CoolingWizard]

@kc1005 ,

Double check your furnace Integrated Furnace Control Board.  It is unusual that it creates a large power draw thus generating the E160 error.  This is identified when, in your system, the air handler/furnace attempts to draw too much current. In the case of the Y wire, that wire is the Air Conditioner and not the Heater.  The furnace control wire is the W wire. 
To confirm this error you need to use an amp-clamp meter with a 10-loop wire multiplier and measure the current draw at the point the furnace shuts off and turns back on resulting in the E160 error.  

AC Cooling Wizard 

[kc1005]

thanks, will do! Stay tuned...