Hello DSAA,
It's great to hear that you're a satisfied user of Google products and that the Next Thermostat is working well in your home. Installing a new one in your garage heating system can be a bit tricky, but let's troubleshoot the wiring together.
For a setup with three wires (green, red, and white) and a jumper for RC and RH, try connecting the green wire to the G terminal, red to the R terminal, and white to the W terminal on your new thermostat. The Nest Thermostats no longer need the jumper wire, so you can disregard it.
Good luck with your installation, and I hope your garage heating system will be up and running smoothly soon!
Regards,
Mark
