The following will allow you to decide when you need the A/C during defrost, instead of having it turn on automatically. This was one of the first things performed when mornings got cool because the A/C puts a big load on the motor. A/C can still be used during defrost by switching fan to blue dots when desired.

1. Remove your cigarette lighter and open the ashtray.
2. Put your fingers under the top lip of the ashtray opening and gently pull. The whole bezel surrounding the radio and heater controls should pop off.
3. Remove the heater/defrost select knob and its white backing piece. These just pull off and are keyed to maintain alignment so don't worry.
4. Just above and to the left of the knob shaft are three ribbons of metal about an 1/8 inch wide.
5. Drill a hole through the lowest one, making sure to sever it completely without cutting the one above it.
6. Put the knob back on and line up the bezel. There are locating posts that you should be careful are aligned.
7. Nudge the clips back into place and reinstall lighter.