I installed a Honeywell RTH2510/RTH2410 thermostat. All wiring was same as old HW stat. Unit is an indoor electric AC/Heat and new stat will only blow hot air.

SOURCE: Household Thermostat Replacement

you have to configure the thermostat to run the fan when there is a call for heat. look at the installation instructions and they shoud ask you if it is gas or electric heat if its electric then you are gong to have to configure it to makr e the fan come on with the heat. Good luck

SOURCE: Ruud heating/ac unit blowing only cold air in heating mode

Do you have gas or electric heat. If you have gas then you do not have a heat pump. You should in most cases have a red,yellow, white, and green wires coming to the thermostat. R should go to rc/rh G should go to green Y should go to Y and w should go to W. Also the switches on back should be switched to non heat pump and gas rather than electric. Hope this helps.

SOURCE: No heat after installing honeywell thermostat H8110U

hook up the blue wire in the furnace cabinet where the blower section and the other thermostat wires are connected to the furnace. the thermostat you have uses a common wire from the thermostat to the furnace and this needs to be hooked up in the furnace otherwise you will have the problem you are having.

SOURCE: I Have a honeywell RTH2410 Thermostat I wired it

What was the old thermostat labels and the wire colors that went to them?
The typical heatpump wiring Terminals are:
R = Red = Hot side of Transformer
C-B-X = Common side of transformer Depending on brand of heatpump
Y = Yellow = Cooling Contactor
G = Green = Furnace Blower
O = Orange Reversing Valve Energize to Cool
B = Blue Reversing Energise to Heat Depending on brand of heatpump.
W2 = White = Auxiliary Heat
You need to be sure where each wire comes from when you connect them to the new thermostat.
The best way to do that is to go to the furnace and see where they are connected. R-Y-G are probably correct, you need to see where the Blue wire comes from and determine what the X terminal was on the old thermostat.

SOURCE: I installed a thermostat and now only blows hot

Hi,
Here is a tip that I wrote about that..

http://www.fixya.com/support/r3869033-replacing_thermostat

heatman101