https://www.googlenestcommunity.com/t5/Nest-Thermostats/e74-error-on-Nest-Learning-Thermostat-Gen3/m-p/404334#M87050 <P>I'm trying to install a Gen3 Nest Learning thermostat to control my GrandAire heat pump/AC. The previous thermostat was a Honeywell Home ProSeries thermostat and it controls the AC perfectly. When I change to the Nest, it says there's no power to the Rh wire, error E74. I used a multimeter to check voltage, and there's about 25V between the red Rh wire and blue C wire. If I change back to the Honeywell thermostat, it works fine again.&nbsp; The wires seem correct: Honeywell had R=red, C=blue, G=green, Y=yellow, O/B=orange, and that matches the Nest wiring (connected red wire to Rh, yellow wire to Y1, others labeled exactly the same). Any ideas why it's not working?</P> Sat, 22 Apr 2023 03:29:31 GMT gcampbell 2023-04-22T03:29:31Z https://www.googlenestcommunity.com/t5/Nest-Thermostats/e74-error-on-Nest-Learning-Thermostat-Gen3/m-p/404334#M87050 <P>I'm trying to install a Gen3 Nest Learning thermostat to control my GrandAire heat pump/AC. The previous thermostat was a Honeywell Home ProSeries thermostat and it controls the AC perfectly. When I change to the Nest, it says there's no power to the Rh wire, error E74. I used a multimeter to check voltage, and there's about 25V between the red Rh wire and blue C wire. If I change back to the Honeywell thermostat, it works fine again.&nbsp; The wires seem correct: Honeywell had R=red, C=blue, G=green, Y=yellow, O/B=orange, and that matches the Nest wiring (connected red wire to Rh, yellow wire to Y1, others labeled exactly the same). Any ideas why it's not working?</P> Sat, 22 Apr 2023 03:29:31 GMT https://www.googlenestcommunity.com/t5/Nest-Thermostats/e74-error-on-Nest-Learning-Thermostat-Gen3/m-p/404334#M87050 gcampbell 2023-04-22T03:29:31Z https://www.googlenestcommunity.com/t5/Nest-Thermostats/e74-error-on-Nest-Learning-Thermostat-Gen3/m-p/407991#M87942 <P>Hi gcampbell,<BR /><BR />Thanks for reaching out to the Google Nest Community Forum. I'd be happy to take a look at this for you.<BR /><BR />Your system may not provide enough power or any power to either the thermostat or a specific wire (so the thermostat can’t complete a circuit and shows a report). Could you please share with us a photo of your thermostat's wiring? This will help us see how they are being labeled. Also, gather the power readings in your thermostat's Technical Info option.<BR /><BR />I'll look forward to your response.<BR /><BR />Regards,<BR />Mark</P> Thu, 27 Apr 2023 17:36:42 GMT https://www.googlenestcommunity.com/t5/Nest-Thermostats/e74-error-on-Nest-Learning-Thermostat-Gen3/m-p/407991#M87942 Markjosephp 2023-04-27T17:36:42Z https://www.googlenestcommunity.com/t5/Nest-Thermostats/e74-error-on-Nest-Learning-Thermostat-Gen3/m-p/409847#M88446 <P>Hey there,</P> <P>&nbsp;</P> <P>I wanted to follow up and see if you still need help. Please let me know if you are still having any concerns or questions from here, as I would be happy to take a closer look and assist you further.</P> <P>&nbsp;</P> <P>Best,</P> <P>Dan</P> Sun, 30 Apr 2023 20:08:27 GMT https://www.googlenestcommunity.com/t5/Nest-Thermostats/e74-error-on-Nest-Learning-Thermostat-Gen3/m-p/409847#M88446 Dan_A 2023-04-30T20:08:27Z https://www.googlenestcommunity.com/t5/Nest-Thermostats/e74-error-on-Nest-Learning-Thermostat-Gen3/m-p/410514#M88605 <P>Hey there gcampbell,</P> <P>&nbsp;</P> <P>We haven't heard from you in a while so we'll be locking this thread if there is no update within 24 hours. If you need assistance or want to discuss topics, feel free to start a new thread.</P> <P><BR />Cheers,</P> <P>Dan</P> Mon, 01 May 2023 20:31:16 GMT https://www.googlenestcommunity.com/t5/Nest-Thermostats/e74-error-on-Nest-Learning-Thermostat-Gen3/m-p/410514#M88605 Dan_A 2023-05-01T20:31:16Z