I have an OLD thermostat. 8 terminals. 6 wires. Here's the problem.
When I popped the front, 4 of the wires were attached for sure: Y=Yellow, R-Red, G=Green, Blue=COM.
The other two wires are Orange and White.
Around the terminal that reads W2, there was a piece of wire, as if a wire (either the Orange or the White) had been attached, but broke off.
The three other terminals are E/W3, O, and B. From what I can tell they were not used.
Now I am trying to install a Honeywell RTH3100C. The terminals are: E, Aux, Y, G, O, L, R, B, C.
I am not certain if the Blue wire goes to B because there is no corresponding COM terminal.
And I am not certain if the Orange and White wires are required. And if they are required, where to put them.
As an experiment, I attached the Blue wire to B, the Orange wire to O and turned the power on.
The unit working and is blowing cold air. BUT IT WON'T TURN OFF. I have to turn it off at the breakers.