88 mustang heater problem

hey my 88 mustang gets neither heat nor cold from the heat ducts or wutever you call them where normally the heat comes out... luckily heat still comes out of the defroster.. Or else it would have been a cold winter lol. i bought the car with this any many other problems. Does anyone have any idea what might cause all of the heat vents not to work for cold or hot air?

thanks
Justin

sounds like a vacum prob under the dash is it running rough at all? or do u hear like a suckin noise coming from under the dash?

sounds like a vacum prob under the dash is it running rough at all? or do u hear like a suckin noise coming from under the dash?

no sucking noise that i can hear..but sumtimes theres a rattling sound.