apneablue

Ok...so after taking a 3 week vacation I had to jump start the 7...thought it was just the battery but after a long drive the battery refused to hold a charge...first I took it and had pepboys check it and they said it was fine...So I ordered a new alternator and a new battery just to be on a new page from the git go...now the battery holds a charge for about 3 days and then it dies where I have to jump it again...then it holds the charge for about three days and on and on it goes...

When the battery is charged the PFC says it's 13V..don't know if that helps to diagnose anything but thought i would put that in there.

Any idea what this is...I am a bit lost on this one...

Turbonut

iTrader: (1)

If alternator is supplying correct voltage to the battery while the car is operating, some circuit must be draining the battery when car is unused. I would say need to check circuits for a drain. You could always, just for a test, disconnect the battery while the car is unused and see if it starts after the 3rd day when battery is reconnected. This would then take the batttery out of the equation if the starts.

FDjunkie

Sounds like you need to verify that the alternator is actually producing the correct voltage and that it is reaching the battery. The manual contains a step-by-step troubleshooting procedure for this, but a quick test might be the following:

One or two days after charging the battery, open the hood, connect a good voltmeter to the battery terminals and read the voltage. Expect something like 10.5-12 volts. Now turn off all switches, light, and even the radio, start the engine and have someone hold the engine at a high idle, say 1,500-2000 RPM. Check voltage again which should now be around 14.1-14.7 volts. Next turn on the headlights and fan to high, and with RPM's still up, check voltage one more time. Should still be over 14 volts.

If your voltage at the battery is lower than 14 with the engine running at this fast idle and with or without the electrical loads, you may have a wiring and/or alternator problem.

Was the alternator new or rebuilt? I has seen problems with some rebuilts. Many autopart dealers can test your alternator and will do so at no cost, you just have to remove it first.

caramanrx7

I recently purchased a new Die Hard battery from NTB for my FD and it never held a full charge. Within the first month I returned it and got a new one that works fine. It is possible to get a bad battery off the shelf!

hercdriver

iTrader: (2)

check your glovebox light (make sure it isn't staying on, guess its a common problem).

RonKMiller

I know this sounds overly simple, BUT - how about some new pos and neg cables as well? They are dirt cheap and you should be able to find a universal fit at NAPA or Batteries Plus instead of OEM. Buy the thickest you can find, copper ONLY.

Battery cables actually do wear out, since traces of acid can "creep" up the cables and corrode them internally. Wierd.

"If you hear hoofbeats, don't go looking for zebras"

Good luck!

skunks

I think something is grounding itself.

Have you checked current draw from the battery?

to do this, simply get a multimeter with an amp/current reading and disconnect the battery (with the engine off). after this, place the multimeter between the pos terminal and the pos cable and check the reading, the ghost reading should be about .2 amp.

report back on what you get

good luck

cournal

you have a battery drain from one of the circuits. like turbonut said.

Brentis

I just tried starting my car to no avail. After reading this post I went and checked my car. While it is still new to me yesterday, I was looking around in the back hatch and noticed a light with a switch on it. - Said, huh, this is pretty cool cause I can't see a damn thing back here. Low and behold, I forgot about that neat little light - now my battery is dead

Street King

Do you have an alarm?

apneablue

yes, I do...think maybe it's going off? maybe I should disarm it and see if it makes a difference...I haven't been able to diagnose the problem cuz the car has been off the road for close to a month now...

Also, there is another thread that was just started just like this one...I am not alone!

ttpowerd

LOL...thats my thread! Sorry, I did not see this one. My problem is very similar and I am going to start checking around tonight. I might even install a cut off switch for security as well as to kill any connection the battery has with the car as to prevent this *crosses fingers and goes to battle!

apneablue

What do you suggest as a cut off switch...what kinda switch will handle that gauge wire? this is actually a pretty good idea for security as well..

MazdaMike

if u have aftermarket alarm/power locks that could very well be the problem. happened on my truck try pulling the fuses and waiting it out for a bit.

twint78

CHECK LIST.

MAKE SURE DUSES ARE CORRECT FUSES.

MAKE SURE WIRE TO ALTERNATOR IS VERY TIGHT ON POST,THIS WILL CAUSE IT.

GET A VOLTMETER AND MAKE SURE THE ALTERNATOR WIRE FROM THE ECU IS GETTING THE CORRECT AMT OF VOLTS AND SIGNAL IF ANY.

MAKE SURE ALL GROUNDS ARE HOOKED UP.

CHECK FOR ELECTRICAL GROUNDS AND POWER TO HAVE NO SLICES OR OPENINGS IN THE WIRE ITSELF.BASCIALLY MAKE SURE ALL WIRES ARE INSULATED.

MAKE SURE NO OPEN WIRES ARE TOUCHING TOGETHER.

WE COULD ALL SAY IT COULD BE THIS IT COULD BE THAT.BUT THESE ARE ALL SYMPTOMS.GO THROUGH THIS CHECKLIST AND WILL BE HAPPIER IN THE END.

THANX

LONG LIVE MY V8 3RD GEN

Joe Still

Done the same battle. Resting voltage thru pos cable and battery after disconnecting is -2.4v Alternator shop says try a little 12v bulb between bat and pos cable. If lite burns draw is too big. Believe it or not this may be cables. Any connection to humidity? My died omly when it rained