Make sure that you have 3 pole plugs on the cable (1 ring), not 4 pole plugs (2 rings) - unless the cars Aux jack has a mic input - then make sure that youre using 4 pole (2 rings) plugs on the cable. Crossing the type of plug will cause problems. (Once in a while you dont have the plug all the way in and it works.)

How do you fix a loose aux cord?

Plug the hot glue gun into a power outlet and turn it on High if it has a power setting. Wait for a small amount of glue to ooze from the guns tip, which indicates that the gun is hot. Place a dollop of glue onto the loose headphone port, then press it firmly to the board beneath it to fix it in place.