Voytek

I have measured between 650 mA to 780 mA draw. It seems to be too high, isn’t it? Is there anything else connected directly to the battery bus, other than alarm, radio and clock?

Thanks,

John Speake

Hi,

A tenth of that might be reasonable.... how did you measure ? You need both doors closed to switch off the tell-tale lights in the dge of the doors.

Voytek

Hi John,
I belive doors were closed, but I am not sure if hatchback light was ON or OFF. I will try it again today. But thatks for the input on the draw magnitude. Now I know that something in not right. My Stinger battery did not start my car after 5 weeks of not driving (Christmass, New Year, etc).
Thanks,

Steve 88

What is the recommended method for measuring the draw? Thanks

John Struthers

FWIW
Somewhere in the 81', or, 82' MY owners manual there is a reference to what I
consider a factory notice that after -I believe it states 5 weeks-a given period of time the
battery may need recharged.
I'll look it up, if I haven't imagined the statement and get back to you.
Since I was -and still am- fighting electrical glitches and drains I found the statement to be
an admission of sorts by the factory that there were 'DRAW' issues built in to the system...
Who Knows?

SharkSkin

I doubt you'll see it detailed like this in the Porsche documents, but here is what I would recommend:

First, run the car. Drive it around, get it hot, etc. Now park it and once the fans quit running(if applicable), using some sort of alligator or other clips on your ammeter leads, clip one lead to a good ground and clip the other lead to the ground strap from the battery. NOW disconnect the ground strap from the body. This method will allow you to measure the current without ever interrupting power to the system. Then, of course, reconnect the ground strap before attempting to start the car or you will toast the meter.

I see people(even "pro" mechanics) make the mistake all the time, of simply disconnecting the ground lead then connecting the ammeter between the ground lead and the body. The problem with this is, there may be some circuit which normally remains latched "on", drawing current until you disconnect power. Then, you connect the meter, and end up scratching your head because the current draw looks normal.

HTH

Steve 88

Thanks, Dave. Definitely print-and-save quality instructions.

SharkSkin

No prob... also, be aware of the door and hatch switches for interior lights. Be sure to take these into account somehow during your testing.

jim morehouse

I've been chasing a draw in my '88. PO said it was around 45ma when he tested it. I'm drawing 135ma. Still working to isolate it. A good tool to have is a 'door buzzer' tool that lets you leave the door open but this spring loaded clamp holds the door button IN so you don't trigger lights. It's a NAPA 700-2406 or Thexton 442. Cost is about $10.

To facilitate measurement while I was pulling fuses, I used a 10' pc of lamp cord with alligator clips on each end. Then connected one end to battery neg and chassis ground and the other end went up into the passenger footwell so I could connect to my ammeter.

Good tip on the power up/down sequence...hadn't thought of that.

Wally P told me that there a number of devices that are on the 'unswitched' or 30 bus run inc the fuel pump relay, lh brain. I'd first try pulling fuses and see how the current drops. Before that look for 'taps' or other non OEM runs for an alarm or stereo install and try disconnecting them. The try pulling relays.

I'll let you know what I find in my when I get back to it.

Jim

Voytek

Jim, in my 1987 there are other two Control Units connected directly to battery bus: Alarm Control Unit and Central Information Unit. I will be checking them as well to see where the drain comes from. I will use Dave's test procedure, even though I got my HI reading with system disconnected first.

jim morehouse

Ah! More leads to check out, thanks!

Jim

UKKid35

There are two immobilisers fitted to my car, one might be original, the other is definitely aftermarket, the total current draw is 40mA. However, this has to be measured as Dave A recommends, although perhaps for a slightly different reason; if you connect a battery that has previously been disconnected, the alarm/immobiliser and maybe other systems will draw significant current until they return to sleep mode (this blew the fuse in my meter - Doh!)

UKKid35

Here is a good place to start http://www.nichols.nu/tip800.htm

Possible canditates also include sticky Rear Window Defrost relay, as well as bizarrely the memory seat function (perhaps this is because the servo can't find the right position and keeps trying to correct). Also check that none of the interior lights are set to permanently on.

Bill Ball

In my 89 the PO had 250ma drain that was traced to a shorted door lock mechanism. That was fixed, and I've not had any problems.

SharkSkin

Ouch Paul... You must have a lot of gadgets, or not much of a fuse.