I have a 7.3 diesel and I have been going through alternators. I bought the truck used knowing it needed new battereis and an alternator. When the shop replaced the alternator it was a bad one and they had to put a new one in the next day. It lasted about 18 months, and then went bad. A few weeks before it went bad I got a new cd player in my truck that has a touch screen and dvd player with built-in bluetooth. Basically I have went through 3 alternators in 4 months since I've had the cd player and I dont know what is causing it. I replaced the starter because it was bad, but it seems to still be sluggish on the 1st start of the day and my I had to get jumped off yesterday. Is my cd player the cause? I only have the stock speakers and don't watch DVDs.

 

you could disconnect the CD and see what happens for a week. I think i would consider a volt meter and amp meter to monitor what is going on and what draw you have on the system. If it cranks slow in the am, that means battery is low (night time drain) or alternator dont put out enough charge during the day.

 

You need to have the full charge system checked out to find the issue.
Here are some things I would want to know.
1. What condition is the batteries in and not depend on the just replaced position.
If even one cell is bad a battery can never charge to float causing the alternator to charge to excess full time and overheat and wear the brushes.
2. What is the performance of the alternator?
Does it have a shorted or leaky rectifier stack?
Is the regulator doing the proper charge and float control?
Of course cable/connector condition.
Somewhere in all this is the answer.
Good luck.