Here is a link for free online service manual, it may also be available at your local library.
http://www.oplin.org/databases/proxy...%2fframerq.asp
enter 123456789 for library card number submit
click on the box with a library in it and more will appear, click on the Public Library of Cincinnati and submit
scroll down to Auto Repair Reference Center ARRC submit
choose year, make, model and engine
Go to TSB's and Recall's and scroll down to Heater and AC system tsb, choose the Poor Heater Performance TSB 24-03-94.
Does your heat lever on the control panel bounce back 1/8th inch when moved from cold setting to hotest setting?
TSB 24-03-94 has a procedure to readjust cable for blend door.
Good Luck