When contractor installed the gas furnece, he did not connect the wires from Central A/C to the furnece. I connected two wires white and red coming from A/C unit to the furnece, the AC unit works but the blower fan of the furnece does not go on. I just need your help to figure out how many wires of which color to connect to the furnece terminal.

A green wire needs to run from the G terminal on the thermostat, back to the furnace, where you should find a G terminal someplace,usually at a terminal strip or control board.

Thank you very much for your help. G wire is already connected to the furnace. Let me explain the current wiring connections. There are five wires Y, W, R, G, and B wires running from the thermostate (Honeywell) to the Goodman gas furnace. All the wires are connected to corresponding color terminals on the furnace except B wire which is not connected to the any terminal on furnace. There are five wires running from outside AC unit to the furnace but only two wires R and W wires are connected to the furnace R is connected to Y terminal and W to the C terminal. With existing connections nothing works, but when I connect both R (from thermostat and AC unit) wires to the R terminal and both W wires to the C terminal, AC unit works but blower fan does not work. Would you please help me with this problem, I really appreciate it.

Thanks,
Nilesh

Here is the normal wiring:

The five wires going to the thermostat should be as follows:
The red wire should connect to the RH on the thermostat and the R at the connecting strip on the furnace.
The white wire should connect to the W on the thermostat and the W at the furnace.
The yellow wire should connect to the Y on the thermostat and the Y at the furnace.
The green wire should connect to the G on the thermostad and the G at the furnace.
Now the blue wire should not be connected to anything at either end.

The wires fron the condensing unit should be connected as follows.
Use the red wire and the white wire. Connect the white wire to the C at the furnace and connect the red wire to the same connection that the Yellow wire from the thermostat is connected to, which will be the Y terminal on the furnace strip... Important unplug the power while connecting the low voltage wires.

Thank you very much that was a big help. The A/C is working now.