Alternator/generator/regulator problems of the 2002 Chrysler 300M

The engine light comes on and the mechanic would put the car on the machine but he could not find out what was wrong. The radio was the first to go out. There has been several times when the alarm system came on while I was in the house and there was no one near my car. Three years ago, the speedometer was not working one day while I was driving, but it started back working. Now there is something running my battery down over night. The alternator is alright and I replaced the battery. The tire pressure display is not working.

Electrical issue started about six months after purchasing my 2002 Chrysler 300m. The lights would spontaneously flicker for no reason while driving. This happened while driving at night, luckily lights came back on. Battery drains out every 3-6 months. At the time of purchase the car was still under warranty- the dealer claimed they were unable to fix a problem if it wasn't occurring at their shop; alternator checked and was working. The battery issue has not been resolved. A year ago the problem with the 3rd gear began. I was driving with my children when the car seemed to have down shifted, it felt heavy. The car has also turned off while driving one time. Input/output speed sensors replaced, transmission oil changed, ground wire checked .