Nest thermostat charging issues believe gen 3 learning nest thermostat

[Josh3044]

Need help my wifi went down on my nest thermostat and say low power I've been charging it but dosnt seem to charge I need help 

[CoolingWizard]

The Nest Learning Thermostat, Generation 3, charges by the HVAC 24VAC system.  It receives the power via the R and C terminals. If you have a Volt Ohm Meter you set it for AC Voltage, put one lead on the R and the second lead on the C and you should read  between 23 and 27 VAC. 

[Patrick_Caezza]

How do you have your Google Nest Thermostat wired? Is there a C wire installed?

Nest thermostats are designed to work without a common ("C") wire in most homes. During installation, a small number of customers may find that the Nest Thermostat does not receive sufficient power. The Nest Power Connector or a C wire may be necessary. See g.co/nest/cwire for details.