Our old thermostat display stopped working but the thermostat would still turn on it would just shut off right away. So I assumed it was just broken. I bought a new thermostat and now the fan and heat work but hot air comes out when it is on cool.

The wires we have are:
Green
Yellow
Blue
Red

On the old thermostat the Green went to G, the Red went to R, The Yellow went to Y and the Blue went to O.

The new thermostat has holes for G,Y,W, Rc, Rh. And I connected Green to G, Yellow to Y, Blue to W. and the Red to the Rh with the jump included. I can't seem to figure out how to make this work. Attached at the bottom is the instructions for the new model. Thanks


http://customer.honeywell.com/techlit/pdf/69-0000s/69-1799.pdf

Do you have a heat pump?

To be honest I have no idea. I do not believe so. I live in my roomate's condo in Arizona and all of the equipment is on the roof.

In many cases the O is for a reversing valve and those are in heat pumps. If that is the case you might have the wrong type thermostat.

I bet it's a heat pump. What is the brand of the old thermostat?

The old thermostat was a honeywell. Model T8400C 1099. I figured thermostats were pretty standard so I didn't even check to see if it would work.

See here. Your old thermostat. Look under page two figure 6.

http://customer.honeywell.com/techlit/pdf/PackedLit/69-1484.pdf


It says O can be used for single stage heat pump systems. I believe you will need a thermostat with the O in order to change over the reversing valve from heat to cool. You need a different thermostat.

Purchased a new thermostat today(for a heat pump) and it appears to be working fine.

Thanks for the help!

Glad it worked out for you.