Condenser wont kick on?

Ok bear with me while I try to explain this. I put in a new thermostat a few months back, everything worked fine, or so i thought. Now that the hot weather is here I noticed the Fan wont kick on, We checked the condenser outside, that was working fine. Decided to put the old thermostat back on to see if that worked, well now the fan works but the condenser wont kick on. Im sure this is a wiring issue, but this is where it gets screwy. When i took the old one off a few months back 2 wires were twisted together, when putting the new therm on i untwisted those wires and put them in their rightful place as marked on the therm(obviously i screwed up somewhere) now when putting the old one back on, I cannot remember which 2 wires were twisted together but I am pretty sure this is whats causing the issue. Anyone able to help out it would be greatly appreciated. I am a female that has no idea what shes doing, but its hot and with 3 kids i need to figure this out, i could just wait til the hubby gets home but i dont want to sweat all day. THANKS!