BlackGT4.6

hey guys, I've had this mustang now for 5 years (2000 GT 4.6l), it worked perfectly and all of a sudden last year the car would not hold its charge for more then 3 days without getting boosted and I have brought it to ford and they changed the battery at least 3 times, and after that it still had the same problem, so I brought it back to ford and they ran a diagnostic and could not figure it out even then, so I bought one of those kill switches that mount on the battery terminals and it worked fine for about a year and then stopped, so now the car only starts if it is boosted and will only start back up within 5 minutes of it being off, im just really confused any help would be appreciated, i thought maybe it could be the alternator but as i said it starts within 5 mins so im not to sure, thanks in advance

BlackGT4.6

anyone?

siggyfreud

Perhaps a bad/corroded connection to the starter. I'd check your positive, ground, and switched power to the starter and see if something needs cleaning/tightening and/or replacing.

Nuke

We're not familiar with the 2000 model (you're in the 2005-2013 forum). But I'd consider checking the windings of your starter motor. If they're cooked then it would take higher voltage then the battery to turn it over and a jump is typically at a higher voltage.

JCON

Wouldn't it require a higher amperage not voltage? A jumping car is probably running as high as a 14V and my battery sits around 13.5V when off. My guess was the alternator or a corroded contact somewhere but I don't know much about the 2v 4.6L so whatever I say could be wrong.

Nuke

In a healthy motor, it would draw higher amps at lower voltage. In the OP's case, it's likely both but initially upon starting, an initial higher voltage would likely help start the motor turning if the windings were degraded. And since the starter solenoid kicks out the motor in short order, the additional running current disappears quickly. Without more info, that's my guess: a bad starter winding.

Mr.Ski

Altenator/voltage regulator problem. Sounds like it is either under charging or the voltage regualtor is sticking in discharge. 2000 altenator set up is different that how ours works.