[eagle]

Use a wiring diagram and a voltmeter and start troubleshooting it methodically. If you don't feel you're up to the task find someone who is. Any reputable mechanics shop will be able find your problem if you supply them with a schematic. They are available here, use the search function. There is no way anyone here is going to be able to give you a reasonably accurate answer with the info you gave us. Just guesses.