license plate lights wont work on 1995 Ford Explorer

ive replaced the bulbs but nothing worked. i read online that it may be a bad ground connection between the socket and bulb so im gonna clean it and coat with some vaseline. if that doesnt work any suggestions?

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1 answer
Best thing to do is to get a hold of the electrical diagrams and start testing.
here is a good source for those:
http://bit.ly/mitchell_repair_manuals_online