Nest thermostat error E74
What it means: The thermostat is not detecting power on the Rh wire from your heating or cooling system.
Some models show it as E73.
- Brand
- Nest
- Appliance
- Thermostat
- Code
- E74
- Can you fix it?
- Often, with simple checks
What to do
Check that the furnace or air-handler door is fully closed: a switch behind it cuts power when it is open.
Check the breaker for the furnace or air handler and reset it if it tripped.
If you have a humidistat, make sure it is turned on.
Tools you need
- Flashlight
Related repair guides on iFixit
- Nest Thermostat E Troubleshooting (device page on iFixit)
- Nest Learning Thermostat 3rd Generation (device page on iFixit)
- Nest Learning Thermostat 2nd Generation Battery Replacement (repair guide on iFixit)
- Nest Thermostat E battery replacement (repair guide on iFixit)
These open on ifixit.com.
Sources
- Google Nest Help: Troubleshoot thermostat power issues (E73, E74 …) Meaning of the code
Not the official manual. Codes can mean different things on different models; check your owner’s manual too. The steps above are written by Sureno from the manufacturer’s advice.
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