Hello I have an 84 Mustang for my daughter and have replaced alternator, Battery and selinoid. While driving the car and turn blinker or lights the car will just stop and have to jump start. But if let sit for long time it will start with out a jump.
Any Ideas.

 

Have you tested the output of the charging system to see if it's working correctly. That's the first thing I would do.

 

I will do that and what should the output be for 3.8 V6. And if it is good what else would it be.

 

While running the charge output should be around 13.5-14.2 volts. You should also have the amperage of the alt output checked as well. Under full charge load, w/e the alt is rated at, the output should be very close to that. have it checked at a local shop you trust.