Error 74 on nest gen 3 with my heat pump

[Raedler6]

I was changing my Nest out and when I rewired it I get an error e74. I have a heat pump and six wires. Yellow in Y, Green in G, W in W2/aux, red wire is in Rh and blue in C. What am I doing wrong? 

[Markjosephp]

Hello Raedler6,

It seems like you've made the right connections based on the standard wiring for a heat pump with a Nest Thermostat. However, the E74 code indicates that there might be an issue with the wiring or that the system might not provide enough power to a specific wire.

Here are a few things you can check out:

1. Inspect the wires for any signs of damage. If a wire is frayed or damaged, it could be causing the error. In such cases, you may need to replace the damaged wire.
2. Try restarting the thermostat. Sometimes, a simple reboot can resolve communication issues and errors.
3. If the issue persists, remove the C wire and leave it disconnected.
4. Gather the power readouts in the Technical Info with and without the C wire connected.

Remember to turn off the power to your HVAC system before making any adjustments. Let us know how it goes.

Best regards,
Mark