Dead or weak Battery issues ?

[britdave]

I have a 2002 996/911 , lately I have been driving the car a lot more than I have in the past (I only have 24K on the odometer ) Point is, on several occasions whilst out and about I come back to the parked car,and the battery sounds very weak when I crank the motor,or has failed to start at all, requiring me to jump start it.

Now, this is not just,a battery issue, I have had several Dura last batteries in this vehicle over the last few years (From Auto zone) Even when I have used the car on a regular basis, with a new battery in it, drove about 60 miles on the highway at 70 mph + get to my destination,and it still cranks weak, or dies on me,on the 2 nd try !

It's really frustrating, and I have to keep a Porsche brand battery tender connected to the car most of the time,as this let down happens often, even after it has been hooked up to the tender,it lets me start it initially in the garage, and sounds strong,but after I get to my destination, park it and come back a little later it's weak or fails !

A friend of mine had a 2000 996/911 and had the same problem if he left the car sitting over a week it wouldn't start. It frustrated him so much he sold it and bought an M-5. He told me the electronics in a Porsche are running all the time so that makes the battery weak ? I love my 911,but as I said,this happens all to often, with new batteries, with regular daily use, even with the tender attached,which I do most of the time. Please, can anyone advise , HELP !!! :help:

[Loren]

Sounds like a possible alternator problem.

What does your charging voltage read on the instrument cluster when running?

It should up around 13-14 volts - you can verify that with a voltmeter.

[britdave]

Yes been there, done that,its charging fine. Does this happen often ? How about what my friend says about the electronics running all the time ? Dave.

[Loren]

Ok - then check the load on the battery using an ammeter (amp meter in series).

The load with the key off (and removed) should be 40-60 ma.

If it is not then start pulling fuses one at a time until you see the load drop to normal.

That will narrow down the circuit with the current draw.

[britdave]

Loren, when the vehicle is at home in the garage, I keep it unlocked so no alarm is on, the only thing taking any juice is probably the clock or some other tiny instrument ? Therefore there should not be any drain right ? I'll do what you say with the amp meter, shall I put its leads on each terminal + & - or what ? I'm not to good at electronics so could you be a bit more specific ? Have you heard this type of complaint before ?

[1schoir]

Connect the positive lead from the amp meter to the positive terminal on the battery and the negative lead from the amp meter to the negative terminal on the battery.

Then, pull off one fuse at a time from the fuse tray and observe the reading on the amp meter each time that you pull off a fuse. If there is no change in the reading after you pull off a certain fuse, re-install that fuse and move on to the next one.

Regards, Maurice.

[fpb111]

The ammeter needs to be in series to read current draw

.

Remove the neg battery cable.

Hook the positive of the meter to the neg of the battery

Hook the neg of the ammeter to the neg battery cable.

Don't let the cable touch the post while you are doing this or you will not get a reading.

Now the ammeter is in series and will be able to read the current passing through it. Don't try to start the car with it hooked up this way. You will fry the ammeter. Unless it has a huge capacity, like 60amps.

If you open the frunk

expose the battery

put the ammeter on the windshield

run the wires to the battery compartment

hook up per above and see more than 60ma draw. ,

turn the ammeter to face inside of the car so that you can see it while pulling/replacing fuses, the meter will be right in front of you saving a lot of running around.

Edited November 30, 2012 by fpb111

[Loren]

Others have answered your meter questions...

Have you heard this type of complaint before ?

Yes, that is why I suggested reading the no-load current draw.

Usually it is some addon accessory or some other part that has shorted or is causing the problem. Remember 40-60 ma is normal for unlocked - car "off" - no key in the ignition.

[RFM]

Loren, when the vehicle is at home in the garage, I keep it unlocked so no alarm is on, the only thing taking any juice is probably the clock or some other tiny instrument ? Therefore there should not be any drain right ? I'll do what you say with the amp meter, shall I put its leads on each terminal + & - or what ? I'm not to good at electronics so could you be a bit more specific ? Have you heard this type of complaint before ?

For normal operation with minimum power drain ( approx. 0.03 0.04 Amps.) the car should always closed by the remote. Under all other conditions remain a number of control boxes in stand by mode, and not in the needed sleep mode. This may lead to a higher power drain.

[fpb111]

You might want to check the power lead from the alternator to the + jumper junction in the engine compartment. There have been bad crimp connections that cause that wire to overheat and melt. That could be why your alternator doesn't seem to recharge the battery.

Edited November 30, 2012 by Loren

[britdave]

Thanks for all the advice guys, I'll get back to you after my trip out of town. Whats funny is, at the Rolex 24 last year, at the Porsche corral (here in Daytona) two other guys with 911's said they had the same problem ? A weak or dead battery, so I'm not the only one, the mystery continues ? It's hard to believe no one else out there has had this problem ? Some times I feel like a kid plugging my "Hot wheels" vehicle in ,every time I come in the garage :lol:

[Rapewta]

Just a friendly word of caution...

Most Volt-Ohm meters only provide an AC current reading function.

Not DC, which is what you will be monitoring.

I just replaced the battery in my 996. The cronic problem I had was that it would

take at least three or four tries to crank the engine over.

The battery just refused to charge past 52%. Everything worked fine but when the battery was required

to turn the engine over (the heaviest current draw by far), it barely succeeded.

The alternator was providing good charging voltage, so I just replaced the battery and it has been about a month now and it starts up on the first try every time. Good luck.

[JFP in PA]

Just a friendly word of caution...

Most Volt-Ohm meters only provide an AC current reading function.

Not DC, which is what you will be monitoring.

Interesting comment, I've never seen a multimeter that did not do DC; we currently have four different brands (and price point) meters in the shop, they all do DC.........

Edited December 4, 2012 by JFP in PA

[Loren]

I think he may be talking the real cheap (Harbor Freight) types because my Fluke multimeter does DC amps.

[Rapewta]

I have a Fluke 87 VOM that will read "series" DC current.

I also have an Ideal 61-702 that doesn't.

Shop technicians and avid home mechanics more than likely have meters that read DC amps.

You are right in that the cheap meters might not have that function.

That's all I was saying. If someone is going to go out and buy a meter, check that it will read DC ma's.

[britdave]

Back to the original topic. Ok does anyone else have this problem where the vehicle starts ok, you drive 16 miles or more, park it, return an hour or so later and it is a very weak start,or fails to start ? Apart from all that is previously written, ref a drain, a friend alerted me when the engine is hot , the solenoid to it sometimes fails,also the ground wire,has corrosion. Several 911 owners I have spoke to mentioned this unreliable starting problem. It's NOT the battery, the drain is minimum when the vehicle is parked in the garage, any other suggestions ??? :help:

[JFP in PA]

If memory serves, ther was a TSB on the 996 for ground wire corrosion issues, you might want to start there as a bad ground will make the car hard to start when hot and reduce the battery charge as well. The ground cables can be tested for resistance with a multimeter.

[judgejon]

you might have an intermittent unpredictable short in the alternator. Is it a rebuilt? OE? Seems like a dumb idea, but this falls into the topic area of "mysterious Porsche issues for which there is no known answer." Like a mysterious rattle or short that cannot be duplicated when you take the car into the shop to check it out.

also, is your battery strong enough? A Dura? Get a strong Interstate from an indy garage and see what happens.

[DBJoe996]

britdave - the starter. Mine did the same thing...got worse and worse. Engine cold, good start...engine hot and it would take many attempts to start. Starter would just not work, no clicking, no spinning...nothing. After doing everything else, i.e., battery, wiring, corrosion cleaning, replaced the starter. No problems after 1.5 years after replacing. Starts first time every time.

[britdave]

Thanks DB Joe (apparently we live close, ref Daytona, I'm in Ponce Inlet ) I believe THAT could be my problem,the starter that is. I guess I'll just wait till it fails again. Thanks Joe, see you on A1A sometime :D

[smak]

Not sure if this link will help.

http://forums.pelicanparts.com/porsche-996-997-forum/408495-alternator-repair-regulator-replacement.html

[britdave]

Very informative thank you ! Does just testing the alternator help ? Does Autozone etc do this ? If needed I will buy a new alternator,however I guess I should check / clean the ground strap, and other things first. I hope thats the cure ???

[Ericginpa]

I was having hot start problems with mine. There is an updated starter/alt harness available from Porsche. It's a heavier gauge cable and is longer so it can be routed outside the intake runners before connecting to the starter and alternator. I got it from sun coast was only about 100 bucks took about 2hrs to change out the old one. It requires removing the alternator and working through that space to access the starter. It fixed my problem lights are brighter and shows about .5 volt increase in charging.

Edited January 7, 2013 by Ericginpa

[logray]

It helps to remove the throttle body and T-tube behind it to access the cable mentioned in the previous post. DO NOT drop anything in the intake. Put duct tape or something over it while you are working on top of the engine.

Yes autozone or most parts stores test alternators for free, with a fancy report.

[Hilux2400]

If I were you I would check the cranking voltage. First check the battery voltage with ignition off and key out. Anything about 12.5V should start the car (my 996 will start with the battery reading 12.3V) . Turn the ignition on and check the battery voltage when the starter motor is cranking the engine. It should be above 9V. Many cars will not start when the cranking voltage is below 9V. Such a low voltage would indicate a poor earth, bad live connection to starter motor, poor solenoid action, faulty starter motor. None of these problems will be solved with a new battery.

H

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