Cargo lights not working

[ncyrider]

2001 model, just replaced the 3 bulbs in the high mount brake light above the rear window. The brake light works but the 2 white cargo lights do not. Heard this can be caused by a ballast going bad...where is it? Or what else could be the problem?

 

[Kjhadfield]

It maybe simple in that you already checked but the socket isn't corroded or anything

 

[ncyrider]

I'll check again, but the brake light works fine after I replaced a burnt bulb. There are no signs of corrosion in/underneath this light assembly. I heard the Explorer suv's have the same problem and it's some kind of ballast in the rear door. I don't know where it would be on the sport trac...