RPM's fluctuate when AC is on 97 Galant


My car fluctuates rpm’s intermittently when the car’s ac is on. Every ten seconds or so the rpm’s drop just a little bit, not drastically. It only happens on a hot day when the AC is taxed. The AC blows cool air not cold at that time. I just recently had the AC charged and a general tune up. Also the thermastat on the car was recently changed. Another item, that may or not be related- the alternator is degraded. (My wife had AAA jump the car after leaving the lights on, and the AAA guy checked the alternator and said is was going bad) I don’t know what is causing the problem, any ideas? Thanks


Check the voltage. HVAC systems use a lot of power and can stress the alternator.