New Programmable Thermostat Blowing Hot Air

Last night I (my boyfriend) installed a new Honeywell Programmable Thermostat (RTH6300B). We gave it a while to cool down but after a few hours set at 72, it was still 84 deg in my house. My unit is in the attic, so I went up to listen- the fan is blowing (warm air) and it seems like 'something' is trying to start-up. It is no longer dripping condensation- no surprise since its not cooling.

A few things I noticed (but I know nothing) are:
1) There was no Yellow wire. I have RC, W, & G wires- which were labeled as such on the Thermostat. But I've been reading some posts and wondering if the lack of a yellow wire is a problem.

2) This is a Heat/Cool 5-2 day Digital Thermostat but my system is for Central Cooling only; I have gas/hot water/radiator heat on a separate thermostat.

Before we replaced it, I had an older round cool-off-heat/fan-auto-on/mercury tube thermostat; but just for the cooling system. It would continue to run after it reached the desired temp & sometimes the fan would run unnecessarily, but at least it was cooling the house down.

It's consistently 90 degrees lately & my allergies are horrendous with the windows open so... Please Help!

-M

Usually the yellow is used to activate the A/C.
Check the fuses on the outside unit.

But there is no yellow wire and the A/C was working before we switched the Thermostat..?

What was the model number and brand of the
Old thermostat?

If you used heat with the same thermostat with out switching a switch on the furnace, its impossible that the thermostat did heat and cool with the info you gave.

We connected the White W wire to the Y and all is working well. Think it was labeled incorrectly before. Thanks to everyone for your help.

-M

Come heating season,, you`ll probably have the same problem again,, hope not

wmproop. I feel the same way. Something is wrong with this picture.

come heating season,,,,,you`ll probably have the same problem again,,,,hope not
Note she said she has a separate heating system on a different thermostat. Maybe it will be okay after all.

It could be but you should always follow the wiring code OR reidentify the wire for the next person so this problem will not present itself again.

It could be but you should always follow the wiring code OR reidentify the wire for the next person so this problem will not present itself again.
I totally agree with this! Especially since the next guy may still be YOU!

Good practice would be to note which wire goes where on the old thermostat before removing it.
I've been known to overlook this simple thing myself. :o