Battery Drain

I'm onto my 3rd AGM battery in 3 months ... last two were tested bad after a couple of weeks - I fully charged the latest one 13.4V on my charger - battery reads 12.98V after unplugging charger. Pulled fuse C3 (windows, interior lights) and measured voltage drop Hour 0 = 12.98V Hour 10 = 12.33V Hour 20 = 11.9V Hour 34 = 11.65V I'm planning to get one of those current test adapters you can plug into the fuse socket to look for drains on other circuits - but what would be the most likely candidates in your experience for such a fast drop in charge ? This has been going on a couple of months now - if I leave car for more than2 days - locked - will not start . Thanks

Assuming you haven't just had the uncommonly bad luck to get ahold of 3 bum AGM batteries in a row, the power drain could be anywhere. It appears to be a big drain though so it may not be a bad light switch that is keeping a trunk or engine compartment light on even when the truck or engine compartment is closed. You need something to measure current flow then I think my thinking would be to remove all fuses and ensure there is no current flow then re-install the fuses one row at a time until you detect a big jump in current flow. This at least tells you in which row the circuit's fuse resides. If you go this route or something similar, anything that has you removing more than one fuse at a time, be darn sure you note which fuse goes to which fuse holder as you do not want to get these mixed up.

Why remove them all at once? Just go through them one at a time, removing and replacing while watching the meter.

It does sound like you have a parasitic drain to track down. What is the voltage if you charge the battery and leave it disconnected for 30 hrs? Just an (unrelated?) comment on the AGM batteries that I have had experience with. My 1972 911 had two in parallel for 14 years that were still in service and working fine when I sold the car. I just changed the one in my 1998 BMW R1100RT after 13 yrs. I am still using it as a portable power source for trouble shooting trailer lights etc... The one in my 2003 C2 is fine at 4 years.

Quotes source post: 11868526

What brand AGM gives you that life? Do you use a battery tender if not regularly driven as well?

The 1972 got battery tender when ever I wasn't going to drive it for ~2weeks. The bike goes on tender when I park it. The tender is right above where it gets parked in the garage, so it is just put it on center stand plug it in & go. The 72 had Marathon "Miata" batteries. They were the only ones that would fit at the time. The Bike has Westco. The 2003 has Braille. I put it on tender during the winter when it doesn't get driven much. Braille have gotten way too expensive. I would probably go to a Sears AGM now. http://www.braillebattery.com/index....ightweight_agm One of my friends has an eight year old AGM in his DD BMW (330IX?) that never gets a tender.

I have a similar problem, also with a Targa, and also would like to know what could be using the power. Plus a question - what's an AGM battery? Edit: never mind about the AGM - I read a few more battery threads.

Quotes source post: 11868496

My thinking was to remove them all and determine a base line power consumption. I would expect this to be zero but if not it might be useful to know this going forward. I'd replace fuses for lights and things like lights first and the security module and DME last. When the fuse for the DME is installed the power consumption will shoot up quite a bit and take some times -- maybe several minutes -- before it drops to the whatever the low power mode power consumption mode is for the DME. But I guess there is no harm in doing it the other way.

Remove the negative battery cable and connect an ohm meter between the neg battery post and neg cable. The background current draw should be about .04 amps. If its higher, remove fuses one by one until the current drops and that circuit has the problem, probably a short of some kind.

Just a thought.....Is you car locking correctly? You should not hear the horn beep. If you do, then it's not completely locked and could be draining the battery as it keeps it unlocked. I believe it takes a charge to keep it unlocked but nothing when it is locked completly. After 5 days the car goes into a sleep mode and the key in the door is the only way to wake it up. Mine is a 99 BTW. Let us know what you find...

Quotes source post: 11872108

Use an amp meter it will work better. Most decent digital multi-meters will give you fairly accurate readout in milliamps. Even a cheap one will give comparative draw.

Quotes source post: 11873012

Hurdi, no offense meant to you. Many folks repeat this but I think this is an "Old Wives Tale". Someone please educate me out as to why an armed, locked car draws less current then an unarmed, unlocked car? Especially during the first ~7 days until it goes into Hibernation mode.

Quotes source post: 11868262

FWIW......I had what I considered excessive battery drain while the car was parked up for a few days and would need to keep it on the charger. That problem went away when the ignition switch suddenly failed and I had to replace it. I've had no such problems since.

ok - I got my multimeter adapter for the fuse box - removed fuses one at a time to measure current draw. All fuses at <= 0.03 A except C3 (interior lights) and B1 (cluster). C3 = 1.3A (door open) - but drops to ~0 when door is closed, locked and lights are out as you would expect. B1 = 0.3 A when door is open (cluster lights are on) - but again drops when door closes and cluster is off to 0.03A. I charged battery and then removed positive cable - voltage stays at 13.05V for over 2 days now. So battery is probably good. I measured resistance on C3 with postiive battery cable disconnected - as I would expect = high resistance (so no leak to ground). I measured resistance from positive battery cable to batter ground (positive able disconenncted) - meter shows 200 ohms and gradually increases to 1000 ohms plus over 10 seconds or so (as battery in multimeter charges some caps presumably ?). I did not look at relays yet - I will also try the suggestion of measuring current from battery negative post to neagtive cable with positive connected. (but I assume I should have seen current across fuse terminals if there was a leak to ground on one of the fused circuits). (Did that - current measures 0.7 to 0.3A intially when I connect the meter but drops in 1 second to ~0.1A drain) Any other good idea ? (Voltmeter on dash when engine is running shows ~13.8V - a bit less at idle - so I assume that means battery is charging properly from alternator) Cheers -MB

Quick question... have you gone through ALL the fuses? In all the different fuseboxes?

03996, i had the same issue with my ignition switch causing a little more draw. Whenever you have an electrical problem with this car that's the first place to start looking. It amazing how many systems it affects.

Gone through all the fuses in box by drivers left foot. Is there another place I should be looking ?

Quotes source post: 11873012

Yes - car locks properly without a beep (just lights flash)

Quotes source post: 11888682

I replaced ignition switch over a year ago - if there was drain caused by that I should see it on multimeter I assume ?

I also read a post from the 964 forum - someone had similar issue - battery drain - but couldn't see any leakage at the fuses - turned out to be alternator with failing diodes that were creating path to ground - has anyone seen anything like this on a 996 ? Do you know if just voltage regulator can be replaced or if I need to replace with entire rebuilt alternator ?

Quotes source post: 11889475

Long story short, Yes. As the drain got worse the alternator became warm to the touch on a cold engine.

Quotes source post: 11889475

Regulator can be replaced. Not sure that it contains all of the diodes. "These sites reference the different part numbers and various companies offer a replacement part for the Bosch part. These companies usually only have one part number and list ALL the Bosch numbers as equivalents. Here are a few of several possible sources of information. I would like to suggest that you google the part numbers yourself to double check. I have satisfied myself but I cannot guarantee 100%. I can tell you that my car is behaving perfectly with the F 00M 145 350 part. (Ref; http://www.woodauto.com/Component.aspx?Ref=VRG46473 OR http://www.mercedesshop.com/shopforu.../t-187174.html Finding a voltage regulator Through various sources I found and confirmed that the Bosch number for the regulator in the Porsche alternator is F-00M-145-225. It would appear that this part isn�t actually listed anywhere as a separate item, although I did manage to track one down on e-bay. All is not lost though, as the same part is available under different part numbers. Various websites cross reference the above part number with the regulator for various Volkswagens from the similar years as well as Audi�s and Mercedes. For reference a commonly available part seems to be the F-00M-145-350 or F-00M-145-341 for VW, Audi, and Mercedes which fit perfectly. These sites reference the different part numbers and various companies offer a replacement part for the Bosch part. These companies usually only have one part number and list ALL the Bosch numbers as equivalents. Here are a few of several possible sources of information. I would like to suggest that you google the part numbers yourself to double check. I have satisfied myself but I cannot guarantee 100%. I can tell you that my car is behaving perfectly with the F 00M 145 350 part. (Ref; http://www.woodauto.com/Component.aspx?Ref=VRG46473 OR http://www.mercedesshop.com/shopforu.../t-187174.html OR http://www.jnelectric.com/bombridge....umber=F00M1453 50&manufacturer=Bosch&description=Regulator%2C+Ele ctronic ) I suspect that the different vehicle manufacturers insist that Bosch supply parts with a unique part number or that Bosch manufacture identical parts in different locations and assign part numbers to each."

I've been trying to track a drain on a 04 996 C4S cab. No fuses have any effect. 500mA drain. Car locked, all switched flipped to make car think everything closed. Alternator removed. Doesn't change..... Needing to get my durametric back and confirm all roof switches are working. Past that look at the ignition switch.

Diodes are soldered to the back of the alternator so you need to get your alternator rebuilt or get a reman one. The regulator is a different component which you can replace to cure low voltage problem.

Quotes source post: 11890240

Any aftermarket hidden electronics on the car? E.g., lojack. I heard some cab owners install smart top or something like that. Did you really mean even with all the fuses removed, you still see a 500mA draw?

Quotes source post: 11889927

Checked Alternator after leaving it overnight - not warm. I'm going to get battery tested again - I can;t believe I would have 3 bad Sear's AGM's in a row - but I don;t see any drain in the system - so perhaps ? I saw way to test alternator diodes on the bench - my multimeter has diode test - but seems like I would have to take alternator out to do this since + cable is at back of unit ? I'm also going to see if I can see AC voltage - but again - can only test at the battery I think when alternator is running - so not sure how accurate that would be (AC voltage would mean diodes are not working properly).

Quotes source post: 11890841

Can you tell me exactly how you tested for battery drain? How did you read the current? The easiest is to get a low amp DC clamp, leave the hood, frunk, and driver door open but manually flip the door lock Hood latch, and frunk latch. Then arm the car and put the amp clamp around the battery cable. Can also put it on the cable that goes to the engine compartment jump start terminal where alternator leak will show. The car will suck a couple of amps for the first 10-20min then it will draw about 20mA or less (from my memory), which is normal. From your battery reading, looks like your draw is 1~2A so it shouldn't be difficult to track.

Quotes source post: 11890288

Yes, all fuses pulled, still 500mA after sitting locked for 1 hour..... No aftermarket devices can be seen. Though I haven't torn everything out of the car.

Quotes source post: 11890869

Yes - I would also be expecting to see 1a plus drain. Had doors closed except frunk - removed frunk bulb - removed ground cable from battery and connected negative lead from multimeter to negative battery post and positive lead to the battery cable to complete the circuit ... So meter was in series with battery at negative side

Targa and Lizard, if after removing all the fuses at the driver kick panel and the 40A SAI pump fuse at the relay panel behind the right rear seat and you still see drain. That will become more difficult to trace. There's alternator as mentioned but there is also a power distributor below the passenger dash that holds very high amperage fusible links that power directly a few modules/circuits such as the alarm, ABS, ignition switch, etc. One can trace all those circuits in the wiring diagrams. Maybe you can see how easy it is to unwrap the wires coming out of that distributor and put the amp clamp around each one to id the offending circuit and trace from there. If you have Durametric, maybe you can unplug one module at a time and see if that makes a difference ad reset any error codes that you may trip.

Btw, this amp clamp may be good enough for 0.5A+ drain MASTECH MS2108A 400 AC DC Current Clamp Meter: Dc Amp Clamp Meter: Amazon.com: Industrial & Scientific MASTECH MS2108A 400 AC DC Current Clamp Meter: Dc Amp Clamp Meter: Amazon.com: Industrial & Scientific For lower drain, you may need something like this Amazon.com: GTC CM100 1 mA to 100 Amps AC/DC Low Current Clamp Meter: Automotive Amazon.com: GTC CM100 1 mA to 100 Amps AC/DC Low Current Clamp Meter: Automotive

Quotes source post: 11892337

This could possibly be a faulty ignition switch if it is fed from the power DB below the dash and not the fuse block.... I know the OP has replaced the ignition switch last year but I had to replace mine after only 6 months use - it just crapped out on me internally.

Quotes source post: 11892384

Agreed. I haven't tried it but will disconnecting the ignition switch prove it one way or another? Or may as well change it if you need to get to it anyway? I would expect the drain stops once the switch is unplugged.

Quotes source post: 11892343

Thanks - Just ordered the Mastech meter from Amazon. The Harbor Freight model does not measure DC amps. When I disconnect the ground cable of battery to put my regular meter in series I think the drain goes away. I ran the car today. Checked alternator charge voltlage (14.2 - including under load with lights on etc.) and for AC current at battery - none seen (so diodes probably good). (alternator was also cold to touch before I started the car). After run - battery was at 12.52V. Over the next few hours it dropped to 12.35V. (in ~ 4 hours). I checked current across all fuses again - not more than 60ma total seen. I didn't start pulling the relays yet - since I need the clamp meter to measure the drain at the battery first to see which one makes a difference. I did check temp of all relays - including the ones behind the rear seats - no component was warm - including Bosch DME. Check temp of ignition switch under instrument panel - also not warm. (BTW - on the targa - it is easy to access the panel under the carpet behind the rear seats from the open hatch !) I'm thinking now that there is a relay stuck on causing current to drain to some component after I turn car off. Must be one of the ones that does not run through standard fuse panel however. When I pull battery ground the relay resets ? Is that possible ? If I get the meter by Tuesday I will try pulling the relays one by one. Hopefully it is not the DME itself - but if that was drawing large current I would expect it to be warm ? Thanks for all the pointers so far guys ....

Quotes source post: 11892343

I also have spare ignition switch - so will try that if the relays are good. But if switch was shorting to gound some how - I would expect to still see that drain after I remove the battery ground and connect the ammeter in series ? (if I do that I still only see the 60mA drain - not a bigger one - and 60Ma is not enough to make my battery drain so quickly ...)

To successfully chase the drain, one important rule is to duplicate the exact condition when it happened. When you remove the battery ground, you disrupted power to many modules and when you reconnect, some modules may boot up while others that were sleeping before the disruption may no longer turn on. The drain may no longer be there. Enter the amp clamp and you will see exactly when and how much the drain is. If you put the clamp around the engne ground cable and see drain there, it means that's something on the engine itself such as the alternator. Again, leave the driver door, frunk, and engine lid open but flip all their locks manually and then arm the car. Clamp the battery cable to see the current goes down as the modules go to sleep. After 1/2 hr or so if you still see anything > 50mA, then you need to start looking.

So I'm still pulling 2+ amps now with ignition off, door closed. Measured with multimeter between battery negative cable and battery terminal. I tried a second battery just to make sure not something strange with the battery - and same result. Have now pulled every fuse and relay - makes no difference - including the relays behind the rear seat. Pulled ignition switch cable tonight - draw is still there - so I don;t think it is the switch. Alternator is not getting warm - so I don't think it can be that (if there was 2A short to ground in the Alt. it should be getting warm ?). So there must be some sort of wiring short to ground that is not blowing a fuse ? Not sure where to look next - I think I will have to go to the indie next and see what he thinks. (BTW - car drives fine - just did 400 miles down Highway 1 past Big Sur this weekend - but battery almost dead over night ....

So logically the 2 amp short to ground must be unfused. Some wild guesses that may prompt more intelligent guesses from others : 1. There is a badly connected/shorted (unfused?) after-market component ? 2. The +ve cable from the battery is leaking to ground somewhere in a circuit before any fuse. 3, Using the clamp meter, tracing along the +ve cable from the battery ,how far can you go finding current before there is a big change in amperage ? 4. Can you disconnect the wiring harness from the back of the alternator to eliminate it? Good luck !

Did you wait for 1/2hr to 1hr before measuring? If you did, I think you will need to dig deeper such as looking under the dash, behind the radio, center console, etc. for aftermarket devices. Also may have to go after the power distributor to check exactly which circuit the current is going through (by using the amp clamp). Also, did you ever scan the car with durametric or alike to see if there are any hidden error codes that may point to some failed components?

You need to break out the wiring diagram and look at unfused loads/current paths. It shouldn't be that hard to find.

Targa...are you having fun? If you are, swell. If not...have you considered taking the car to a Porsche dealer? They might have been able to do all the testing in a tenth of the time and given you an answer. If you have already tried them I apologize but this seems like it is becoming your second career.

As a temporary (and less than ideal) fix there is always battery master switch like this:

Quotes source post: 11911565

I have yet to find a dealer mechanic who can troubleshoot electrical issues like this better than I can. They don't have time to monkey around, they get paid by the job, not by the hour. So they want to fix everything fast.

Quotes source post: 11911594

Yeah - not fun - but the there will be the satisfaction after fixing it ! I'm also not sure I trust a dealer to spend time on it without charging me an arm/leg and/or fixing stuff that is not broken ! Next step is to pull the alternator cables and then current distributor ... But if that doesn't find it - any recommendations of a specifc tech at a sf bay area dealer that is genius with electricals ...

No need to pull the alternator. You can just put the amp clamp around the cable that comes out of the engine compartment positive battery jump point above the a/c compressor. That cable comes from the battery and then via the jump point, it goes to the starter then the alternator. If the alternator is drawing any current, it will show up on this cable.

Quotes source post: 11911594

Exactly... I had a parasitic loss on my Touareg that several different dealers struggled to find. I had an extended warranty, so I thought I might as well let them deal with it. They charged thousands of dollars to the extended warranty company for lots of diagnostics and replacement parts and never solved the problem. Finally found/fixed the problem myself with the help of several internet forums.

Agreed. I had a parasitic loss issue on both a BMW Z3 and a Lincoln LS. Both times the shop kept it for a long time and didn't fix anything. I eventually tracked them both down on my own.

Came out to check the car again today - alternator was warm - rest of engine bay cool - I took the clamp meter and measured 1.8A on the cable from the +ve battery connection in engine bay that runs back to the battery - so hopefully that is now the correct diagnosis to the problem now. I will pull the alternator this weekend and take it to rebuild shop to test / service. Was looking at San Jose Starter & Generator - good yelp reviews - or does someone have a better recommendation in bay area for that ? thanks

Glad to hear it's so simple

Targa, Thank you for posting the diagnosis. So often threads like yours die inconclusively .

Interesting thread.... Wonder if you could just replace the voltage regulator (relatively cheap) and retest? Also, looks like there is some good info on pulling the alternator and replacing the regulator here and here .

Thanks for the link to pulling the alternator - I got to the part when I hammer the bushing in - could not make it budge. Soaked in P Blaster - drift punched on the bolt, then directly on the bushing - it is not moving - so I cannot rotate the alternator anti-clockwise to get it out of the engine. I think I'm heading to the indie next. While I was in there I did notice one of the small vacuum lines from the (brake booster switch ? ) next to the left of the alternator that runs back across the top of the alternator was fractured (the thin metal tube not the rubber hose). I'm not getting any check engine lights - anyone know what the symptoms of that being disconnected is ? (I am getting a slight vibrating noise from the rear on braking from hight speed - but assumed that was warped rotors). thx

Perhaps I am misunderstanding the issue but - Try using a bushing driver or bearing driver of the correct size on the stubborn bushing?

Try a 2.5lb harborfreight orange hammer with a 7/8" x 1' aluminum rod. Give it a few good whacks on the head of that bolt.

You only need the bushing to move 1/8" or so and that's enough. Sometimes it's hard to see if it actually moved.

Quotes source post: 11923230

OK - I will get an Al rod - and try again - what is best way to lever the alternator anti-clock wise ? I can't get enough leverage just lifting alternator by its pulley - Pry bar under long bolt and against engine bracket ? Don't want to damage anything ..

Quotes source post: 11925426

If you can move that bushing just a bit toward the front of the car, no prying is needed. That bushing is the ONLY part that's locking the alternator in place (other than the 2 alternator bolts).

With all due respect to the tenacity of the owner and all here who gave advice, we are three weeks into the car being off the road. I have to believe a trained mechanic would have had this fixed in a couple of days...and even at minimum wage the owner's time must be worth something. On the other hand, I have a brother who has a barn full of non-running hobbies.

Yes. Once the bushing is free the alternator will easily move. I used a very long socket extender and a rubber mallet. I found that I needed to be able to swing the mallet from Outside the engine bay. Otherwise I couldn't get enough force. There just isn't enough room inside the bay.

Quotes source post: 11925781

Change your own oil, change your own pads and rotors, install your own suspension, fix your own alternator, install your own plugs, and most importantly, diagnose and fix what several shops could not... then you will understand. But if you want to just roll your car to the dealer every time a light comes on or a new sound is heard, that's fine. Plenty of Porsche owners roll that way. Speaking of which, what's the difference between a (typical) Porsche owner and a porcupine?

Quotes source post: 11922927

Targa - I hope this is not a silly question, but how much did you loosen the offending bolt before you hit it with your punch? When I changed mine, I loosened the bolt about 4-5 turns before giving the bolt head a good smack. Only then will you feel the bolt is loose and be able to move the alternator around.....

Quotes source post: 11925954

Took the bolt right out - removed the pulley - then screwed it back in - most of the way .....

I read somewhere brass bushing is heat fitted - so after hammering to no avail on the bolt - I went to harbor freight and got a butane pencil torch http://www.harborfreight.com/butane-...rch-41169.html zip tied oil filler tube out of the way - and then put aluminum kitchen foil around the tube and behind alternator rear bracket - just in case. Lit torch - held for 30 seconds or so on aluminum casing around bushing - tapped with 3 pound drift hammer on pulley backed out 3 turns - using 2' (x0.5") aluminum rod I got at home depot (tool rental center cut 3' rod into 1' and 2' length for me) - using towel to protect rear bumper. Bushing moved like hot knife into butter ! Then alternator started swinging out immediately - still a bit fiddly to clear both brackets that hold the alternator bolts to engine - but after 5 mins or so of wiggling - got it out. Pressed on lock for connector plug and this pulled off easy. Nut holding +ve cable was on a bit tight - used PB blaster and long handle wrench on 13mm socket to get it loose. Now off to local alternator rebuild shop. I think with the torch trick - I would have had this thing out in less than an hour (instead of 3 x 1 hour attempts). So hopefully these tips will save someone else some time. Still better than the $1K or so quoted by the shop. And really not hard - after you know how to deal with the bushing. OK time for a beer. From the picture you can also see the reason for all these problems - Bosch Alternator is "made in Great Britain" Did they buy Lucas or someone ?

I know it has been a while. Did the new alternator fix the battery dain problem?

Quotes source post: 13561403

yep - perfect now - the clue the alternator diodes were going bad ...was the alternator body was warm after letting it sit overnight

Quotes source post: 13561615

Thanks for the info...was just curious what happened.