Electrical/heater problem! help quick!

[elvis240sx]

Ok, this doesnt exactly pertain to a 240, but i know that if anyone can help, it would be someone here. I just put a cd player in my friends 99 ford escort zx2. it went fine, so i tossed him the keys and left. the next day he tells me that since i put in the cd player, the heat isnt working. i checked all of the fuses i could find and everything seems ok. so, i took the car up to the local car audio store and the mamager checked it out for me. he said i did everything fine, everything is plugged in ok, and it should work. he has never seen or heard of anything like this happening. he says that i may have blown some type of relay or fuse and that i have to take the car to the dealer to get it fixed! does anyone know what i should do? is there something that i am overlooking, or does anyone here have experience with my problem? please help!!

[yellow_jacket]

Sure you didn't unplug the fan switch somehow?