Problem with Tail light - 02 Mountaineer

Vehicle is 2002 Mercury Mountaineer.

Problem is: One of my tail lights are out. The weird thing is that tail light works with the headlights on...but it doesn't work when I hit the brakes. I tested all of my fuses but they are all good. I even took the tail light off and checked the bulbs. Any ideas would be great.

thanks
john

Your bulb has 2 elements I think its a 3057. One filiment is for the parking lights the other for brake lights.Try a new bulb.

Your bulb has 2 elements I think its a 3057. One filiment is for the parking lights the other for brake lights.Try a new bulb.

You know what...I think you are right. I'll try that and get back to you...Thanks a bunch.

Your bulb has 2 elements I think its a 3057. One filiment is for the parking lights the other for brake lights.Try a new bulb.

You were exactly right 'bustedratchet'. I appreciate the quick response.