I have a 83 928 that has had a battery draining problem for some time.
ammeter in series showing 0.43 with all the fuses pulled. Battery is dead within two weeks. I installed a new battery two weeks ago. Disconnected power to fuel pump. Everything looks fine at altenator and starter. Main positive cable replaced with welding cable. Still has the issue.
Can anyone offer suggestions?

 

Interior lights, door edge lights. There is a method of checking for current drain by measuring the voltage drop across a fuse. If there is no drain, the voltage across the fuse will be 0.0 mv. If there is a drain, it will be 0.15 +/-. You will normally see that drop on the clock circuit and the door circuit if you don't close your doors. All circuits do not go through the central electric panel, however
Good luck,
Dave

 

Unplug the passenger door switch and disconnect the negative battery cable. Get a multimeter and measure amperage across the negative battery cable to the battery. Start pulling fuses and watch the draw. This will lead you to find which circuit is creating the draw.

 

I apologize. I did not notice that you still experienced the draw with all of the fuses removed. Many have luck at cleaning grounds to cure their drains. I would probably start there before going through the wiring diagram.

 

I had that once... turned out to be some hacked in security alarm. Only part of it was left in from the PO and it drove me nuts. I found the culprit under the center console and neatly removed. I've never had a problem since.

 

Doesn't the LH brain have a direct wire to the battery or something like that, two smaller as well as the one big wire?

Old or bad car alarms are a royal pain, and like root canal to remove.

Also I don't think the brains go fully to sleep for some period of time after all the doors are closed.

Many many hours into this myself and I disconnect the ground strap if I can't leave a trickle charger connected.

 

I had a similar problem which turned out to be the pin switch in the bottom of the rear hatch receiver,, took it out cleaned it etc, no more light on when not needed now..,= no more drain issue .

Ken
80 928 S
5 Speed

UK

 

http://www.thetoolwarehouse.net/p-19...ties-306b.aspx

 

What a great idea. Just bought that tool! Been fighting parasitic drain for years. This should do the trick.

 

Paging inspector Clueso ..................roll down the door windows ,
look inside the doors before you close them,
look for the red warning lights to be illuminated,
if the lights dont work then fix them they take special bulbs,
once the lights are working and you know where to look,
close the doors and see when the lights go out.
they should go out after 60 seconds or less.
If the lights dont go out then one of the pin switches wires is making contact thus leaving the lights on.

NEXT get an IR gun and with the battery fully charged and the car sitting for a few hours,
climb in through the window opening so you dont have to open the door .
Shoot the CE panel, this may work better if the car can be left outside and get cold soaked.
Any relays that appear hotter than the rest are an indication of power being applied ,
investigate any relay thats warm.

Shoot the alternator as well after its had time to cold soak it should be at the same temp as the engine

 

( Mrmerlin wrote ) ...., Paging inspector Clueso ..................roll down the door windows ,
look inside the doors before you close them,
look for the red warning lights to be illuminated,

This is exactly how I found my fault

Ken
80 928 S
5 Speed

UK

 

My red warning lights work but do go out when door is closed. I never thought of the IR gun. I'll do that tonight. Still bought the tool though. Seems useful.

Why would the alternator be a different temp? Just curious. Mine is new and the drain time is the same so I am ruling that out but still would like to know.

 

if the alternator is warm then power is running through it,
maybe a bad ignition switch or ignition relay,
or there are too many fuses installed in the CE panel.
run a fuse check to make sure the empty slots are indeed empty.
Do the same for the relays,

NOTE sometimes relays get installed in the wrong slots or additional relays are installed to fill the empty spaces,
this can back feed circuits,
same thing can happen when adding a fuse to an empty slot

 

The CE panel is the dist point for all of the stock wiring which would cause parasitic draw. So, that's usually where I go. As all the fuses are removed and the draw is still there, go through the relays one by one and remove them while monitoring the ammeter.

Once you have taken all the relays out, if the draw still exists, unscrew the hold-down on the CE panel so it will come out of the floor, and gently move it up so you can reach all the connectors arrayed around the side. Learn how the connectors are latched to the edge of the CE panel, then unclasp them one at a time, and disconnect them from the CE panel. Monitor the ammeter as you disconnect each plug. If you get to the last plug, and you still have a draw, investigate the primary wires from the battery into the chassis going forward to the engine bay, and CE panel. I don't know how many there are on a 82 but you should put eyes on each wire as much as possible looking for a broken insulator somewhere.

 

By using the IR gun you can find out if you have a relay or fuse thats passing current it will be warmer then the rest of them so it will give you starting point.

You could also have a fuse thats gotten corroded inside the CE panel this will also run hotter than the the rest of the fuses.
Also drop the CE panel and inspect the gray wires look for shorted wires ,

NOTE wires that have gotten hot will have a satin sheen on the insulation ,
compared to the flat surface texture of unheated wire insulation