"Ian" wrote in message
...
I am installing a new NEST thermostat, replacing an old two wire mercury
bulb furnace thermostat. There are only two unmarked wires. There's 24 V
across the wires.

Can anyone tell me which letters on the NEST base (W, Y, O/B, AUX, E, G,
C, etc) they will map to? It has to be the most basic of installations;
open or close the circuit.

Thanks,

Ian

I've been fighting that battle for months. Thankfully I took still photo
before starting and set up a video camera to record the actual steps in the
process.

Nest is still not working but at least I could go back to where I started so
we have heat.