Non MK7 problem

First, I apologize for posting this here as it is not MK7 related. But I am looking for as much input from anyone with any ideas.

The problem: My sister has a 1999 Mustang GT convertible (4.6 sohc). Lately its been dealing with a battery drain issue that we originally thought was map lights being left on. We bought a new battery that lasted a month or two until recently it need to be jump started (twice in the last week, this morning makes 3).

However, here's the weird part. Yesterday morning the car started fine and got her to school. After school, the car wouldn't start, so she tried to jump start it with a friends car (she knew how to jump a car properly while her guy friends didn't ). BUT it only made the click click click sound associated with dead battery and starter not engaging. So I made my way from work with a jump pack and got the same result. So we assumed starter. Fast forward a few hours and a neighbor was able to meet us with his AAA guy. The AAA guy pulled out his jump pack and the car fired right up! When the car got home, I tested the battery/alternator and it read 14.something running, so I assume I can rule out a bad alternator? Could it be a bad starter in conjunction with a bad battery? It would not jump again this morning with my brothers car.

Any help or suggestions would be great. I am completely novice with car electronics and tracing power draw.

Thanks!

If you are getting 14 V when the car is running, the alternator is charging the battery as it should
When it won't start (click) do the other electrical parts of the car work? Radio? headlights? If so, I suspect the starter solenoid is not working correctly.
This is a 19 year old car we are talking about.
Are all the connections cleaned?

ies99 said:

If you are getting 14 V when the car is running, the alternator is charging the battery as it should
When it won't start (click) do the other electrical parts of the car work? Radio? headlights? If so, I suspect the starter solenoid is not working correctly.
This is a 19 year old car we are talking about.
Are all the connections cleaned?

Click to expand...

She said yesterday everything worked, but the (factory) alarm horn beep was significantly more quiet. We noticed that a) the key fob worked after she got out of school to unlock, but b) no longer worked after the few attempts to jump start, like we drained the battery more trying to jump it.

So after work today I plan on doing a few things.
1) take the battery to oriely to have them test it
2) clean and check her terminal connections
3) take the battery from my brothers car to see if that'll start it

A guy at work also mentioned the solenoid and that the battery didn't have enough juice to start it.

It's probably also worth mentioning that she drives maybe 5-10 minutes each way to school. So I don't know if the battery is getting adequate charge in that time.

+1 on connections 1st

then check voltage both running and stopped. post up what you got. then you may need to check amperage draw while parked.

Strange Mud said:

+1 on connections 1st

then check voltage both running and stopped. post up what you got. then you may need to check amperage draw while parked.

Click to expand...

I remember last night after AAA started it, I was able to start the car just fine. It read 14v running. When the car was off, it read low 12v, like 12.04. I will check it again after work today.

those are both decent numbers...a touch low but ok

You need to check the voltage when it first won't start, before you attempt to jump it. If the battery holds a charge and your running voltage is also fine, but the battery is drained when you leave the car sit, you have a ground somewhere. You can attempt to narrow down where by using and ammeter and pulling fuses, but it's going to be difficult.

oddspyke said:

You need to check the voltage when it first won't start, before you attempt to jump it. If the battery holds a charge and your running voltage is also fine, but the battery is drained when you leave the car sit, you have a ground somewhere. You can attempt to narrow down where by using and ammeter and pulling fuses, but it's going to be difficult.

Click to expand...

^That is the exact thing I'm dreading. I know nothing about that and honestly don't know if I'd find anything. But hey, have to learn eventually!

12.0 is low. Most newer cars won't start that low. You definitely have a drain then.

So here's a question then, if it was just the drain, the car should theoretically start when jumped, right? Or will a jump not work is the battery is drained too much?

Until the battery recharges, it's a drain on the system and can keep you from starting. Hook up your jump pack or second car and leave it connected for 10 minutes before you try to start it.

12.04 volts is not enough. If the battery cables are tight and clean she probably needs a new battery. When they test it make sure they charge it, then put a load on it. There are testers that specifically do this. Make sure your shop has one or you'll need to take it to a Ford dealer.

Get a load test done on the alternator as well, it could be on its last leg.