2002M3Drew

My 911's battery has been dead about a week now. Two weeks ago I did a bunch of little things on the car, test drove it...no problems...covered her up. Last weekend, I go to start her up and there is no power...the battery is dead. I attached my battery tender, but throughout the week the light stayed on red. So today, I hook the jumper cables up to my M3, and realized what caused the drain...the hazard lights were on. Apparently, the button had been depressed to "on" but somehow stuck and stayed in an off position. With the cold weather, it must have come free, unstuck to effective an "on" position, and the lights went on, and the battery was drained underneath the cover in the frigid temps...

Now the fun part...

The car was getting juice from my jumper vehicle, my '02 M3, and all of the lights came on...no problem with the connect. I go to crank the 911 and I hear a faint but distinct "pop" from the rear of the car, and then everything went dead...everything. No matter what position the key is in, nothing works. There is no power to anything in the car. Now, when I first connected it to the M3, the blinkers immediately came to life without the key in the ignition, so it shouldn't have anything to do with that. Did I blow a fuse, or perhaps a relay? Any ideas? Perhaps the M3 has too much juice for the old girl's system?

2002M3Drew

I'm thinking I may have toasted the alternator...any thoughts?

theiceman

What year is your car ? that may help . are we dealing with a DME car or not ? perhaps your car has a fuseable link that has popped . I think once you chime in with the year people may be better positioned to help.

But at first glance if you have absolutely nothing I would suspect a fuse. I can't see the alternator preventing the power going to the rest of the car but ya never know. I have a 78 with three fuses in the engine compartment under the electronics cover on the driver side. may want to check those first. Although htose are engine fuses, can't see it causing a complete failure.

Does your car have an alarm sytem that may have been triggered ?

glenncof

It's hard to believe nothing works. After applying a voltage to the battery terminals you should be able to see the voltage on the terminal block holding the appropriate fuses such as parking lights.

I assume you got + to + and - to - on jumper/battery. I have seen one explode when reversed.

What happens to the M3 idle speed ? You should at least see the dead battery load draw down idle if cables are good. Also check the voltage at the 911 battery. Got to go back to basics....

I don't know about the 911 but many, many years ago I found a huge fuse wrapped "inside" the wiring harness. It was actually low melting temperature wire. This was a primary feed to the non-starter electrical system. I doubt the 911 has this although it may be undocumented as this would occur only in severe breach. I'm electrical engineer and could not believe this. It was intermittent.

emac

Glenn
Your talking about a fuseable link, I know that most older Chryslers had them. I really dont know if Porsche has one. I will take a look in my book and post if I find something.

Droops83

The starting/charging circuits are NOT fused on a 911, or on most German cars for that matter, like many Japanese/American cars are. If you hook up the cables backwards, you can possibly fry a few things! But, I'm sure you would have noticed sparks as you connected the cables if you had done that.

Now, what were the "bunch of little things" that you did to the car before you left it sitting? If any of it had to do w/ anything electrical, or at least moving wires out of the way, make sure everything is routed correctly . . . like glenncof said, check the basics: battery voltage, that all the plug connections between the ignition switch and the fuse block thru the front "firewall" are good, etc.

Also, once you figure out how to get power back, pull the hazard switch out of the dash and take a look at it. Corrosion can and will make em go bad, and although this usually makes the hazard lights not work at all, it can also stay stuck on. Good luck!

---

Chris A.

2002M3Drew

Hi all.

Thanks for the replies. It is a 1983 911SC. I didn't reverse the cables (positive on that!). Everything appeared normal when I connected the cables to the M3. Immediately the car's power came to life, and the offending blinkers (hazards) came on. (This was how I knew they were indeed the cause of the problem...I had originally suspected one of the inside lights.) I turned the ignition, and everything was still fine...idiot lights came on as they are supposed to, the familiar whine from the rear of the car...all was normal until I tried to crank the motor. I turned the key, heard a very faint pop, and everything died...lights, horn everything. The jumper cables were still on the battery. I checked them, reconnected them to make sure they were getting a proper connection...no problems there.

After speaking with Steve Weiner, I have a bunch of things to check before having it towed off...grounding strap, battery wiring, etc. Could be the alternator or a solenoid? I may have severely overtaxed the system by attempting to jump a very dead battery with a newer car on a very cold day. I'll update when I know for sure...if anyone has experienced the same or has any ideas, I'm all ears! Thanks!

WPOZZZ

NEVER jump start anyone with a newer car, or NEVER try to jump start a newer car! Buy a booster pack to start a car as it'll be $50 well spent. When jumping a car with a car, there can be voltage spikes that can damage the electronics in your car. AAA jumped my 750il with another vehicle and it fried my circuit board.

Mike Murphy

That pop sound you heard sounds like a fuse or a bad ground. Check all the ground straps first. Second, take the battery out of the car and charge it with a slow charger for 24-48 hours to get it fully charged. Then just install it back in the car and you're done. If you still don't have power, you'll have to take your voltmeter to the fuse boxes and start checking.

Peter Zimmermann

WPOZZZ: Amen! Any time that I have a battery issue I remove the battery from the car, put it on the bench and charge it with a charger. I used AAA in the past, for an older car, and even then I made sure that the driver used a battery that was not connected to anything else (your battery pack is an excellent solution - I have one of those also).

Drew: Just a thought, do you know if your car was ever fitted with an anti-hijack system that was popular in the '80s? If yes, and someone removed only part of that system, well... The same thought goes for an aftermarket alarm system. Murphy is correct, always start with a fully charged (verified) battery!
Pete

madmmac

Check the main lead running to and connecting to the starter...it would be the only circuit carrying a large load at the time when you attempted to start the car and heard the pop.

2002M3Drew

Thanks, all! When the klondike that I call my NJ home starts to thaw (it's 12 degrees right now), I'll start checking these things. What I learned from this happy little adventure...jump starting is a last resort option only, and completely dead bateries need to be recharged properly before using again. (not trickle charged or jump started/charged with alterator).

2002M3Drew

Problem solved, and it turned out to be the simplest solution of all...it was all in the battery itself. It must have been so low on juice when I went to jump start it that it shorted out.

I had bought a new battery for the car this week, and figured I'd test it for size in the car and to see if the leads would line up properly. Just for grins, I hooked up the leads and saw a slight fizzle at the negative. I look into the car, and the interior lights are on. The car turned over and started easily.

The still baffling part to me was just how the car went so completely dead, even when still connected to the BMW by the jumpers. I would have thought that car would have had at least lights as long as it was connected to the other car. I guess that, with the short in the battery itself, the circuit is broken at that point?

quicksilver

I think what went "pop" is probably the cause of your original problem to begin with. I would pull out the battery and have it bench tested to be sure it is ok. I would check and make sure you don't have a major short before reattaching a charged battery though. A battery is basically a chemical bomb if you have a major short. If it is the alternator you should be able to remove it and start the car (only for a few seconds) without the alternator.

BTW - This is a good time to talk about jumping cars.
If you ask at any auto parts store they will tell you that they won't warranty an alternator or regulator on any taxi or tow truck... Ever.
The reason is that taxis and tow trucks are commonly used to jump cars AND EVERYONE DOES IT WRONG!!!

Why?
The best alternator that you can buy puts out maybe a bit over 100 amps. Any starter pulls way over a 1000 amps. It is a completely overloaded device. If you don't think so pull your coil wire and crank the starter for a minute straight. If the starter survives the battery cables will be extremely hot. How can an alternator deal with that?

Here is the correct way to jump any car:
Connect the first cable to the same polarity post on each end. (I prefer to do the positive connection first) Do not trust the color of the cables or the post protector. Only trust the plus and minus markings on the battery! When you connect the last clamp on the second cable there will be a spark and your battery emits hydrogen so blow on it as you connect it so there isn't any explosive gases at the connection. If you connect the negative cable last you can use a good ground that isn't near the battery for more safety.

So far this has been pretty much the way that everyone does it. Now lets do the correct 'different' procedure. Let the cars sit hooked together while the car providing the jump runs to charge the battery a bit. A little RPM doesn't hurt. Let it charge for at least a minute or two. Now here is the REAL IMPORTANT bit. When you are ready to try cranking the car TURN OFF THE OTHER CAR! You do not want its alternator to try to feed 1000+ amps to the starter. That is what burns up the diodes in the alternator.

If it starts just remove the jumper cables. If it doesn't start you might try charging the battery a bit more but you need to think about what the real problem is and give up before something burns up.

Daniel Dudley

That is a good post, quicksilver ! If a battery is really dead, the longer you leave the cables on it without trying to start it, the better off you are. Otherwise you are trying to charge the battery and draw amps past it at the same time, not good.

Glad all is well.