My Dad has a 1995 Lincoln Towncar that has developed a continuous shrill whistling sound inside the car when you start and drive. No amount of fiddling with any of the controls makes it go away…but …it does stop on it’s own, sometimes.
We have heard all kinds of theories about what it might be; including seat belt warning, turn signal flasher, short in the steering column, vacuum leak, etc. But short of committing to an expensive hourly rate to find the gremlin, we have been unable to solve the problem.
Yeah, the heater / AC blower runs all the time and is a prime suspect…When it happens, set the heater fan to “High” and see if that changes the sound…Next would be a vacuum leak in the heater / AC control system…Manipulate the HVAC controls and see that changes the sound…
Can you give us more info? If the motor is running but the car is not moving, do you get the “continuous shrill whistling sound”? Does the sound change at all when the motor is rev’d up a bit with the car sitting still in neutral? Do you just get the sound when the car is moving? Does the sound change when the car is moving, more speed results in a higher pitch?
The noise might be coming from the automatic parking brake release vacuum motor. Remove the vacuum hose from the motor and plug the hose. If the noise goes away the diaphram in the motor is leaking.