A/C Woes!

[William]

I need a little insight into this before I start tearing into it.
I have an '87 5KTQ - Basically the situation is this, the A/C is
blowing through the heater / defroster vents and not through the front
vents in the dash. Now for the bigger problem: It is blowing a
combination of cooled air and HEAT! So the A/C is cold for the first
few minutes but when the coolant heats up and flows through the heater
core I get luke warm air. I am not a big proponent of using the A/C -
but the past couple of days it has been 90 degrees plus here.
Any thoughts on this would be appreciated.
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