In the middle of our remodel, our thermostat stopped working last night, 1 hour before the hardware store closed. (It wasn't the batteries or the breaker.) I got a Honeywell RTH230B. Out of frustration from the remodel taking so long and the new problem, uncharacteristically I just took the old unit apart before reading the instructions, so I didn't label the wires. Upon trying to connect the new unit I noticed I have 1 extra wire, and a big problem.

My wires are Blue, Brown, Green, Red, White, and Yellow. The labels for Honeywell say Rh, Rc, W, Y, G. The old unit is a White-Rodgers 1F81-51.

I'd rather not go through and test each combination of wire to letter, so does anyone have any suggestions/solutions?

I would disregard the brown and blue, connect the others to the terminal that indicates the color of the wire, if this does not work substitute the blue for the yellow.

Also there should be a jumper between Rh and Rc.

Thanks for the help! When I stopped wanting the internet to find the problem I figured it out. I opened the furnace and found where the wires originated and the letter corresponding to the old, helping me install the new t-stat.

I am having the same problem. I also have the old White-Rogers
What do I do with the blue? My system isn't cooling this summer... do I need to get another thermostat or do I just wrap the blue around other wires.

My solution has been to get an updated model of the White Rodgers that I have. As soon as I figure out how to get it working I'll let you know.

I am having the same problem. I also have the old White-Rogers
What do I do with the blue? My system isn't cooling this summer...do I need to get another thermostat or do I just wrap the blue around other wires.

I purchased a new White Rodgers. It's the 80 series 1F80-361. Because I bought this there are plenty of spots for each wire. The blue connected to the C terminal and the red connected to the O terminal. I wasn't able to get the Honeywell to work, so I returned it and ordered the replacement W.R. online. I had tried just leaving the blue wire out, but it didn't work, that's why we purchased a new one.