Where is the power window relay on a 1999 Ford Mustang?

The 1999 Ford Mustang doesn't use a single, dedicated power window relay in the traditional sense like some older vehicles. The power window system is controlled by the Power Window Module (PWM), which is integrated into the body control module (BCM). There's no separate relay you can easily find and replace.

If you're having power window issues, the problem likely lies within the:

* Power Window Module (within the BCM): This is the most likely culprit for widespread power window problems.

* Window switches: A faulty switch is a common cause of individual window malfunctions.

* Wiring: Damaged or corroded wiring in the door harness or between the door and the body can interrupt power.

* Window regulators or motors: These mechanical components can wear out or fail.

Instead of searching for a relay, you should troubleshoot the system starting with the switches and then checking the wiring. If those are okay, a professional diagnosis pointing towards a faulty BCM is needed, as replacing the BCM often requires specialized equipment and programming.