Furnace only works when emergency heat is on

[ST506]

I do not have a heat pump. I have a gas fired furnace.Heat mode only activates the fan and does not fire the furnace.  Furnace fires when emergency heat is turned on.

yellow wire is on Y

Black wire is on C 

White wire on W

Green wire on G

Red wire on R

orange wire on OB

In the furnace they are all the same except the orange wire is on w2 and the black wire is on B, there is no C

Any tips would be appreciated. Thanks.

[Patrick_Caezza]

@ST506 

Post a picture of the original thermostat's wiring here.