Andy, Sounds like the regulator in the alternator is going out or has gone out. This hot weather all over the country is playing havoc on them. Delco has changed their specifications two or three times in the last couple of years and even though they try to do better, sometimes it's not quite as good in all applications. They try to make one device fit as many applications as possible. We are always looking for the better regulator. I'm am going to start adding a diode in the light wire to try to stop some potential feed back problems. John Hervey http://www.specialtauto.com/