A/C Blower & Controller Problems

[nicosisj@ldcl1.dnet.dupont.com]

The A/C blower on my 5KCSTQ does not alway come on.  It takes slamming the car
door to "wake it up" at times.  I think its the relay that controls this but I
don't know where its located.  Can anyone tell me where the A/C fan relay is
located?  Also the A/C controller sometimes switches the cool air from the
upper dash vents to the defroster vents and sometimes after a few minutes
returns the air to the upper dash vents.  Is this normal?  Sometimes it never
returns to the upper dash vents until the car is turned off and restarted and 
then it doesn't always work....Any suggestions???  TIA

Sal Nicosia
'87 5KCSTQ