When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
you're probably hearing either your ac servo motors or your brake booster. If it's the booster, it's normal to hear it as the car gets older. i'll here mine's from time to time when i stop at a stoplight. What you here is the booster re-filling. It's a drilling sound and then a soft click.
A/C control servos typically make all the nosie back there. Finding it is almost as bad as finding a needle in a hay stack. Best of luck to ya.
who said finding it is hard, have you EVER done your own? actually finding it is VERY simple... when you start the car with or without the glovebox on, reach hand under there and feel the servo. the one chattering will be obvious