I have a 1999 Grand Marquise. In hot weather (AC on) and more when in traffic jams after long city driving, my battery voltage drops down almost to a quarter or below of the battery voltage scale.
I have installed a new battery and a new alternator but to no vail. Battery is only getting about 13.2 volts. What could be the problem?
Thank you for your help and prompt repsonse.
Regards,
Fuad Tmeizeh

If the voltage increases back to about 14 or 14.5 when the engine is above idle, your OK. If not, go to an auto electric specialist for diagnostic. The alternator is not designed to put out max amps at idle.