I purchased a rth2310b and connected the red wire to the RC and white to w the green to g. It still will not start furnace. This is a gas forced air.

The wire colors are for the following functions ......red - 24 volts white - heat yellow - AC green/blue - blower (fan) red is connected to the R with a jumper between R and Rc What type of furnace/heat do you have ???? Electric. oil, gas .Forced hot air, baseboard, steam, heat pump, or ?????? Different systems use different connections and need a specific thermostat for that application !!!

More than likely, this is what you have:

Red- Power- (RC/RH)
White- Heat- (W)
Green- Fan- (G)
Blue- Cool- (Y)

Usually, the only times you need more than 4 wires are:

1. You have a HeatPump system.
2. Your new digital thermostat does not use batteries, which then you have to have a common wire to power the thermostat.

Hey jim Try....RH/RC jumper (connected with a small piece of wire)...RH/RC=RED...W=WHITE...G=GREEN blue=unused... should give heat only (in heat mode) no ac..tks

your blue wire controls the reverseing valve you dont say where you put it. it needs to go back on O

red is 24volt power, white is load,I.E. relay,touch the red and wht wires together, the furnace should start, if it don't the problem is the heater, Rheat-Rcool you have a heat/ac thermostat, no ac forget Rc,try turning thermostat all the way up, dig up a multi-meter or powered light tester, touch Rh with one wire of tester,touch the other wire to different terminals until it lights,hook up your wires, you should have heat

If you do not see a RH/RC terminal then your red wire goes to terminal 4, do you have a heat pump system or a forced air furnace? If it is a forced air furnace green wire goes to the G terminal, yellow or blue wire goes to the Y terminal, the white wire should go to the W terminal and the red wire should go to the RH terminal, (leave jumper from RH to RC terminal.

The thermostat has terminals which are marked for color, R = red, W = white, Y =yellow, G =green. There should be a jumper between Rh and Rc, Hook the red to Rh.

you have to go down to your furnace and follow the thermostat wire ...it connects to a terminal strip or fan centre...the color doesn;t really matter...installers mix and match all the time....look at the furnace wiring and mark it down...Red on "R"...Green on "Y" whatever it is...and connect it accordingly upstairs...if you only have 4 thermostat wires downstairs you will need a jumper wire between RH and RC...if you have 5 wires you will see 2 wires on "R" at the furnace.,...and connect either to RH and RC at the thermostat

disconect the dark blue on the circuit board of the furnace. if there is no central air the c terminal was powering the old t-stat

Your house might be older.  Are your receptacles two-prong, or three?
I would ignore the missing "G" wire, and connect Red to both Rc and Rh, and Y to Y, and W to W.