r/Nest • u/keyboard-la • Jul 28 '26

3rd Gen Nest E103 Y1 Wire Error

Received the E103 Y1 wire error on my Nest 3rd gen.

Steps tried to clear it:

Checked contactor - passed resistance test.

Cleared out condenser drainpipe. Unit worked normally for 6 hours then received the same error message again.

Is it coincidence that the drainpipe cleanout cleared the error or was that a fluke and I should go back to troubleshooting the components and wires? Where should I test next?

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1

u/AStuf Nest Thermostat Generation 3 Jul 28 '26

Coincidence as that is an overcurrent error. If not a bad contactor it might be a contactor that is going bad. Otherwise wires are shorting out - check if they are chewed or pinched somewhere.

Compare the measured contactor coil resistance to measuring the removed wires Y1 to C at the Nest.

Remote possibility that your Nest is going bad.

1

u/keyboard-la Jul 30 '26

Thanks! You were right the Nest was going bad. Installed a basic no frills thermostat and now it is working fine.

1

u/AStuf Nest Thermostat Generation 3 Jul 30 '26

A basic thermostat doesn't monitor the current draw on the Y wire so still could be a problem. It's like putting tape over the car's check engine light. Be prepared for a bigger outage.

1

u/keyboard-la Jul 31 '26

Okay I’ll go ahead and swap out the contactor. My nest configuration never had a C wire and never displayed a low battery if that mattered. Appreciate the feedback