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Please don't flame me, I have searched this and read posts but my little brain can't wrap around this very fundamental thing.
Multimeter is set at 10A, black probe is in COM and red probe is in 10ADC. Reading on meter is point two five (.25). Is this one quarter amp (.25A)? If so, is this excessive thus necessitating the search for a parasite?
Was the hatch or a door open when you took the reading? Was the key in the ignition? Were doors locked?
These all affect what you see on the meter, and in fact what the battery gets to supply when the car is at rest.
Try connecting the meter, and placing it where you can see it with everything closed up. Keys in your pocket, car not locked, let it sit for a while (a few minutes should be enough) then watch to see if the reading drops to something more reasonable.
I find it useful to remove one fuse at a time to see which circuit is contributing to the draw. Usually start with the interior lights fuse as it makes it easier to work with the door(s) open. If the draw drops to an acceptable level with the interior fuse removed it can be a bit challenging trying to isolate it around the door switches, if it doesn't then rotate through removing fuses to see which one helps.
It may be a couple of smaller draws on separate circuits so you might not see a full drop to an acceptable level. I usually place 'aftermarket' items as the biggest contributors to unwanted draws (radio/phone/alarm). My major draw contributor was a misaligned glove box latch that did not depress the door enough to turn off the glove box light. The previous owner had removed the fuse to stop an unwanted flat battery (about a week), but could not find the actual cause.
Usually the are 2 interior light fuses - one for the lamps themselves and another one for the relay, so in terms of defeating the fact that a door is open - this is problematic. I think it is far better to push in the door pin switch to equate to the door being closed, similarly with the hatch - which is also often open to allow reading current at the battery ground connections (in this case you can just pull off the brown/white wire from the hatch pin switch connector - under the hatch receiver).
Thank you all. I tested with the doors closed, key out and hatch wiring disconnected. I removed 5 fuses at a time and tested after each block was removed; the amps did not drop. Someone had removed relay 8 (fuel injection) and jumpered the socket. I removed the jumper and the amps dropped from .25A to .07A. As I read above, I am still to locate another .05A drain. Where else do I look? There are no fuses left in the CE, do I start yanking relays?
.07A might not be within spec on the 928 (I haven't seen the Stuttgart number) but it is definitely within spec on a lot of cars. Early ECUs used a trickle current to retain memory.
Thank you all. I tested with the doors closed, key out and hatch wiring disconnected. I removed 5 fuses at a time and tested after each block was removed; the amps did not drop. Someone had removed relay 8 (fuel injection) and jumpered the socket. I removed the jumper and the amps dropped from .25A to .07A. As I read above, I am still to locate another .05A drain. Where else do I look? There are no fuses left in the CE, do I start yanking relays?
You may have another problem unrelated to the parasitic draw.
With the jumper removed will the car start? Typically the jumper is used when the LH computer fails to energize the fuel pump relay. So, if the car won't start unjumpered you are likely faced with rebuilding your LH computer.
Well that makes more sense Kevin. I was wondering why someone would install a jumper just to save the time and expense of locating the correct relay. Even so, an LH brain is only $200, why do a workaround that is going to be continually pulling the battery down? We'll see how it starts, if it starts, after I get all buttoned back up. This car is just full of little easter eggs.
If there's any even close to correct mod for L-jet fuel pump relay failure, it's certainly not a jumper. Options on just "a jumper" only include running full fuel pump current through the ignition switch 15 contacts. whice were never intended to supply the pump directly. Driving lucky isn't something I depend on since I found out I'm no longer immortal or even bulletproof. Or even flame resistant for that matter. Buy the correct FP relay and install it.
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By the time you get down to tens of milliamps, it's OK to change the meter lead configuration back from the 10A input, and set the range on the meter to 200 mA. From that you'll be able to see changes that don't round to the nearest 10 mA.
Most frequet causes of parasitic drain:
-- aftermarket alarms.
-- aftermarket audio pieces.
-- aftermarket keyless entry
-- sticking rear window defogger relays.
-- other time-delay relays.
-- sticking hatch release
-- dirty relays or switches.
And a reminder that there are more than a few unfused circuits in the 928. Different on different series/years. Diagnosis goes to researching circuits that pass through the various CE panel plugs, then pulling them one by one to narrow down the search at least to circuits within some subset of the connectors. That doesn't help with circuits that don't pass through the panel connectors, but it's still another way to narrow down the possibilities.
On S4-onwards, there's also a timer on the fan controller from memory - when hot, the fans will run even with the ignition off, for a long period after the car is shut off (determined by the intake-mounted heat switch on the rear of the intake).
So you need to be measuring draw something like 40 mins after ignition-off event.
very frustrating dead battery....... the battery is new, like about 2 months old. Closed all doors/ hatch and tested the draw 17mA....please see pic and make sure I am reading this correctly because after a good long charge and showing 100% on the charger, if the car sits in the garage for 2+ days, or sits outside in 30 degree weather for 12-14hrs it will have a dead battery.
11-07-2015, 10:39 PM
Parasitic draw
