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Can't find short (Read 729 times)
butch951
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Can't find short
May 13th, 2019 at 12:39am
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I took my multi-meter and checked all the fuses by touching the top of each.  No short shows up.  Yet, the battery will be dead after 3-4 days.  I decided to check if there was any electrical going on in the fuses.  I touched one probe on number 1 fuse and the other on fuse 2.  Nothing!  I went and did each one.
I got two hits on the fuse board.  When number 25 and 26 showed 12.5V active.  Also, 38 and 39 when touched showed 12.5V.
What does this mean?  I'm lost as to where to head next.  Relay's I can't get probes in them.
Any help and guidance from you guru's of Porsche salvation.
  
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slinger569
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Re: Can't find short
Reply #1 - May 13th, 2019 at 7:01pm
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My suggestion- hook up a meter to your battery and start pulling fuses one at a time watching for fluctuations. This should help you narrow down where the battery draw is coming from. Many have found it’s from an aftermarket radio, a stuck door pin that turns on the interior lights, a car alarm, a bad power window switch, etc etc. pulling fuses will help narrow your search...
Good luck
  

Dave
84 n/a - sold
89 Turbo
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Dave W
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Re: Can't find short
Reply #2 - May 14th, 2019 at 12:23am
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That's not how you check for a battery drain.  Some circuits are meant to have 12 volts at all times.

You want to have the multimeter set to measure milliAmps.  Then you remove the fuse and put the probes on each tab.  This measures the current running through it, not the voltage.

Typical drains are the clock with about 10 mA and the radio memory with about 30 mA.  I don't know what the alarm normally draws.  Anything else would be the problem item.  Some people don't hook up stereo amps properly and they are on all the time.

Even these normal values are enough to drain a weak battery in a week.
  

Dave - black 84 no longer exists. Sad 83 self destructed. All better now. Smiley
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anchor
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Re: Can't find short
Reply #3 - May 16th, 2019 at 12:01pm
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_951,

The 85/5 n/a fuse box has a test socket for fuse insertion. If you are accustomed to that setup all you need is a fuse puller.

Of it so happens your 951 has an owners manual the chart and fuse sizes will have a table. Depending on your measured 12.5 volts set up and if direct at the battery post then there is a way to determine voltage drains by turning on every thing except the rear hatch heater circuit.
Then hooking the positive of your meter to battery positive and ground black lead to alternator ground and determine after you start the full load on what your voltage is system considered. You might desire a new battery cell setup depending which battery type plates and fill type you have.
Maintenance free , gel cell, wet cell.
Measure with a hygrometer the PH if wet cell and use only distilled water. Make certain your lugs are wrenched up_ tight.
« Last Edit: May 17th, 2019 at 9:35am by anchor »  

elect-15_001.pdf ( 26 KB | 13 Downloads )

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