I am trying to install a programmable thermostat. I have 6 wires and am not sure why there are 2 yellow ones connected to the same terminal.

The wires are G, Rc, Rh, W, Y (2 yellow connected to this), and a blue one that isn't used.

Help!

Go to the furnace,check out stat wire from that end ,see what each color is connected to., should be red-to red, white to rc or rh, green to g for fan and yellow to y for a/c,only 4 wire need unless you are talking about a heat pump,