When I bought my 95 Mystique (V6 ATX) in '97, the dealer let me drive it home for a day, as part of the test drive. (It was a 2-year leased car)
At the time, I heard a whistle noise when cruising at low speed in a quiet neighborhood, it was not in the morning, though. The mechanic confirmed the whistle by putting his left foot on the brake, the right foot on the gas pedal, and changed the (automatic) gears from Park to Reverse, then Drive, ... while revving the engine at each gear. Sitting on the passenger seat, I heard the whistle that came on in any gear, Park, Reverse or Drive. I remember that the whistle changes its tune, or it is modulated by different engine speeds, very entertaining
. Perhaps when you drive at high speed, wind noise and engine noise would have masked this steady volume whistle? At cold start, the alternator would have to work harder charging the battery. And if the output diode(s) shorted, the alternator whistle noise would be more pronounced?
The dealer replaced the alternator before I bought the car. The whistle noise was definitely fixed.
Dave
