986 Battery Drain

[MarkGolf]

Hello,

I have a battery drain on my '03 986 2.7 - Goes flat within 6-8 hours, alarm goes off, really annoying. I have an isolator on there now but that means I can't close the bonnet and I don't want to disconnect the battery every time I stop.

The battery is a 4 month old Bosch S5, this has just been tested by the supplier and all is good.

With car running, voltage reads 13.8v

I have disconnected the batter, used a screw driver to lock front latch and drivers door, used my multimeter between earth terminal and earth lead and pulled each fuse out, 1 by 1, I saw no change in the current draw, which was around 3.00

I haven't pulled the relays above the fuse box but assumed I wouldn't have to if I saw no change with pulling fuses.

No interior lighting remains on, boots, glovebox, interior, all go off.
Everything is orginal, alarm, radio. No gizmo's.

Nothing appears to be running, fans, etc, can't hear anything.

So now I am completely stuck as to what the problem is, there is definetly a drain but from where, I don't know!

HELP!

Thanks

 

[deMort]

Sorry .. i missed this post last night ..

First off .. an amp hound is the best way to locate a parasitic drain these days .. whilst its not used often it is a god send as you can read off the current draw of each individual fuse .

Ok .. so i know the 996 does a lambda sensor burn off for approx 30 mins .. this will give the best part of 1 amp discharge on a meter .. to stop it ( cheat ) you pull the dme fuse then reinsert ..

I'm not 100 % sure the Boxster does this but it is logical to assume it does .

normal test with an amp meter and you leave the car for at least 40 mins .. at that point you have an accurate reading of the actual discharge ..

This is helpful as it can point towards certain items ..

Radio / amp issue .. about 1 amp
Alarm siren ( just disconnect the dam thing on a test ) it varies but upto 1 amp although it might pulse on and off .
N/s/f seat tilt button or the seat is so far back its jammed .. 3-6 amps ..

I have seen an umbrella down the side of this seat pressing the tilt button before .

tracker systems .. very rare to be fitted to a Boxster but a pulsed .. every 30 seconds - 1 min of upto 1 amp.

Rare as hens teeth but the battery positive cable .. the bolts for the item behind it come loose and it touches the bulkhead .. i saw 1 amp but it could go higher .. or catch fire !

Disconnect the alarm horn as well .. drivers side of the battery .. just as a check .

Over all .. confirm it is 3 amps .. as thats damn high and i would lean towards a seat motor off hand if it really is that amount ... you can obviously reach under the seats and unplug them if needed .

ok .. so you have tested all the fuses .. no discharge found but still a fault ..

In this case we need to look for non fused items ..

The battery positive lead as mentioned is one .. the alternator is another .. i've had a few different models over the years with alternator discharging the battery .. one was a brand new Cayenne on a PDI check .

Normally approx 1 amp though .

last thing .. control units .. not many i must say but things like the instrument cluster not going to sleep .. try making an educated guess at a £2500 cluster causing a discharge which you can't prove .. i had to ..

It was a long weekend to get the new cluster .. monday .. fit it and then heave a sigh of relief to know i was correct !!!

Amp hound on a fuse lead me to that one although i couldn,t prove it was staying awake .



Please don't share this info with anyone else .. the DME trick is just between you and me :wink:

 

[Lithgae]

I had a similar problem with my 996. It was on trickle charge, as usual, over the winter and I noticed the charger was getting very hot. After disconnecting, the 10 year old battery became completely flat overnight. I purchased a brand new battery and exactly the same thing happened again.
The fault was diagnosed as the alternator regulator, a relatively cheap fix.
Have had no problems since.
Hope this helps

 

[MarkGolf]

Thanks guys!

It was the voltage reg on the alternator!

Really weird that they do this but as you say, cheap and easy fix, no more 3am car alarm wake ups!