I just got a 89 civic hatch dx, and when I turn the a/c on the car starts to shudder at idle .

 

and your ? is what

 

A/C draws alot of power from your car, and the car will bog if you turn it on, especially at idle. Its normal. If you car gets really bad, shuts off, etc i would suggest looking into a new battery/alternator.

dont worry about it