Both times I got this message I ended up calling my HVAC maintenance
company and both times all it took was a shop vac to the outside drain.
If it gets clogged the system will show this error. The drain should
always be dripping and even if it is it ...
I have the Nest 3rd Gen eLearning and got the e73 error code. Needless
to say, I was hot and bothered. This fixed my problem. It was just a
matter of charging it via a USB cable just like charging a cell phone.
https://support.google.com/googlenest...
