I have a friend that owns a '92 Buick Skylark. The fan kicks on when it is supposed to, but it blows out cold air. I have an idea what it might be, but I can't locate the heater core. Email me with this information PLEASE!
in-op heater valve, it is a valve in the heater core supply line that turn's the flow of water off and on. normaly it is a vacuum operated vavle, but i have seen electric one's too.
stuck air door. there is a heater core air door that is opened by a vacuum valve.
i vote for the control valve first, then the heater door. then the core it self. if you notised i go for the part that you can get at the easyest first... . it is also the one that fail's the most by the way.
oh there is one other part that can be the problem. it is called the vacuum manifold. it is the vavle that control's the vacuum flow to the varrious vacuum can's in the heater/ A/C system.
i belive the heater core is berried behind the motor. you have to take apart the dash on the inside to get at it. it is installed as a unit from the inside on this car. get a good shope manual for the car. it is the best $20.00 you can spend to work on the newer car's.