After installing this new Nest learning thermostat, my furnace started to behave weirdly: when the temperature falls, the furnace turns on and the blower turns on, but then both the furnace and blower would suddenly turn off at the same time after being on for maybe 20 seconds, just to restart in a few seconds. It doesn’t always do this but it occasionally cycle like this 2-3 times before the temperature is reached. I reinstalled my old thermostat and the furnace stops doing that, so I did some research and I think it could be a power issue with my Nest since I don’t have C wire. However, the voltage always stays above 3.80V, and both Voc and Vin stays above 30V (even when the furnace is running. Below google Q&A says it should be around 6V since I don’t have C wire… Not sure whether this is an issue) and lin has always been 40mA too (even when the furnace is running). Does this look like a power issue? or is there any potential reason on why my furnace does that?
If there isn't a C wire in your thermostat:
- Voc: 29 to 42V
- Vin:
- 29 to 42V when your system is not running
- 6 to 7V when your system is running
- Iin: 20 to 40 mA
If there is a C wire in your thermostat:
- Voc: 29 to 42V
- Vin: 29 to 42V
- Iin: 100 or 200 mA
