AWasserman

Help. Something has been draining my batter when I am not looking. After leaving the car unused for more than a day, the battery is pretty much drained.

I have hooked up an ammeter to the red line to the jump post under the hood. Once I lock the car it goes to nothing (before I lock there seems to abou a 0.03 amp drain).

The only clue I have is that when I went out today after the car had been parked for a few days and the battery was good and dead, I noticed a ticking sound coming from under the passenger seat. To my ears it sounded like a relay trying to close but not quite making it. If I press a power seat adjustment (for example to move the seat fwd) the ticking stopped for a few seconds.

Does anyone have any idea what this might be...?

thx
Adam

Billu

What year?

jschiller

If this is a late car (S4 or later) try unplugging the large connector under the passenger seat that provides power to the various motors in the seat and see if the ticking stops. Not sure what you have under the seat in an earlier car. The only thing under the seat would be the seat controller and the solenoid that activates the rear AC, if so equipped. Note that there are also electrics under the box on the passenger side door sill with the hatch pull **** so listen closely to see if the ticking is coming from there. The fact that the ticking stops when you activate the power seat probably means the additional current to drive the seat flattens the battery to the point that whatever is ticking no longer has enough juice to activate it.

Mrmerlin

I would be looking for a seat rocker switch that’s stuck in a certain position
I have seen switches where they will stick and kill a battery

otherwise remove the parcel tray and CE panel cover then shoot the relays and see what is hot
roll down windows and keep doors closed verify the door lamps go off look inside the rear of the door

please report what you find

AWasserman

To all: 1991 S4. Sorry, I should have stated that. Another thing I should have stated is that this car was sandwiched between a truck (behind) and a car in front. When I got it back from the body shop, the battery keeps draining. The body shop is in another country 2,000 miles away so no suggestions please about bringing it back to them and letting them figure it out.

To jschiller: I'll try that, but nothing think I should have mentioned is that when the battery os full, there is no ticking or other noise. So whatever is ticking only does it win the battery is flat That means that I will have to unplug and then see if my batter goes flat again or not. But that's okay. It is the stage that I am at with this.

To Mrmerlin: I have tried all rocker switches, and I have been super careful about door lights (yes, people do tend to kick them on when exiting!). As for hot relays, I might have to do that. It would mean keeping the plywood cover off of it all the time and parking it with the windows down so I can go feel the relays after about 8 hrs of sitting there without opening the doors (which will activate a whole bunch of stuff, screwing ups my testing). Not as easy as unplugging the passenger seat, sos I will that one first.

Again to all: what really confuses me is that when I pop the hood, then lock up the car, there is no drain -at all - on the batter as measured by an ammeter at the jump start out under the hood (I removed the hood light bulb). So what ever does this starts up after the car has bee sitting for a while. What and why on earth would there be something that kicks in after a period of dormancy?

Thx
Adam

RET

I think that you should be checking current drain at the battery: I don't know about a '91, but my '89 has other wires attached to the battery plus connector which provide current paths in addition to what you can measure at the jump post.

FWIW, if your 928 has a rear AC, there is a solenoid mounted on the floor under the passenger seat that controls the refrigerant to the rear evaporator.

Good luck. Tracing a parasitic drain can be a real PIA.

Wisconsin Joe

I'm going to guess that the 'ticking' sound is a relay or something that is closing, putting a load on the nearly dead battery, drawing the voltage down to where the relay can't hold closed, then releasing.

Think about the solenoid 'death rattle' when trying to start a car with a nearly dead battery.

Does it have memory seats? Pretty sure that module is located under the seats. If it's doing something 'stupid', it could well be drawing enough power to kill the battery overnight.

For seeing if the relays are hot an IR temp 'gun' is really handy for this. Prop up the plywood CE panel cover and just reach in an open window.

Billu

My guess is that the ticking is a symptom of the low voltage and might not have anything to do with the battery/drain.
Have you load tested the battery?
A failing battery can exhibit this.

Alan

It's probably the late model Alarm unit. You will need to remove the passenger seat, Then the metal cover. Then unplug the 2 connectors on it and see what happens.
You can't get to it with the seat in place.

You will lose the alarm, central locking and interior lights - but if this fixes the drain you will need a new one or find a way to get it repaired

Alan

dr bob

With access constrained as you state, consider that the "clicking under the passenger seat" may as easily be "clicking from just in front of the passenger seat", like anything in the CE panel in the passenger's footwell. There are no relays or other clicking opportunities under the passenger seat beyond the alarm unit that Alan describes, but the cover next to the seat holds the audio amplifier and the engine cooling fans controller. Neither of those have 'clicking' capability.

Current drain needs to be measured at the battery, typically and easily at the ground strap that lands at the rear bulkhead crossmember behind the tool panel cover. The loads on the battery include those passed through the jump-start post under the hood, but also include dedicated connections at the battery positive post for fuel injection, fuel pump, oxygen sensor heater, and the cooling fans. The fuel injectors and the oxygen sensor heater do not have fuses but do have relays, with the heater powered through the fuel injection relay. Regardless, a good ammeter in the ground will detect all the possible current flowing through the battery. There's a two-pin Molex-style connector that sits near the bottom of the small vertical brace behind the center of the tool panel. Disconnect that, and the interior lights and alarm trigger for the hatch are disabled. You can get current readings then with the hatch open; else you need to set up the meter and close the hatch completely.

On that note, body shops like to work with the doors open a lot, so may have turned the interior lights off at the lamps themselves. That leaves the red safety marker lights in the doors still active if any door or the hatch is detected as open. Make sure that at least one of your interior lights is set to be on with door open, then take a look with doors closed to make sure it actually goes out. There's a time-delay for lights going out, BTW. Make sure the keys are not left in the ignition switch while the car is stored.

Did the body shop do any welding on the car as part of the work they did?

Last but no least, I've gotten in the habit of removing batteries from cars going for bodywork and paint, or resign myself to the idea that it will need a new battery when it gets back. Even disabling the door and interior lights with fuse out, body shops still seem to figure out ways to kill batteries. They don't always like having to push the car around without the battery. I used to wonder if the heat of the curing oven was contributing but that's much less of a problem since the move to more water-based coatings. Regardless, check the battery health on the way to your troubleshooting the possible drain.

AWasserman

RET: Good point thx! I have cut off all the hatch switches so I can open the hatch without changing the battery drain.

Wisconsin Joe: Your diagnosis is the same as mine, great idea about the heat gun, thx.

Alan: you are the man, so I will try that if Dr. Bob's suggestions don't pan out.

dr bob: I actually opened the door (since the battery was so dead that not even the alarm light was flashing) and got real close. But since your suggestions are easier than taking out the passenger out, I'll start with yours .

Thanks everyone
Adam

dr bob

Should also mention that I keep the car on a maintainer between uses. I was doing a lot of travelling for some years after I got the car, and found that storage without the maintainer for more than a week or two meant slow cranking at best. If you car is just sitting, at minimum you'll want to lift the ground strap connection to keep normal parasitic drain in the car from trashing the battery. There's a recent discussion from Alan about a NOCO 2A on-board maintainer option. For ~$40 it's a day-saver.

AWasserman

Yes, I have noticed the 928 just wants to be driven. Every day if possible.

Maybe I need to wire up a kill switch that lifts the ground so that I do not have to go through the rigamarole of pulling spare whatchamacallit (it is not quite a tyre, is it?)

Thx,
Adam

sendarius

I think the suggestion is to lift the OTHER end of the earth strap - the one that bolts to the body outside of the battery box, at the base of the tool panel.
There is no need to lift the negative battery terminal at the battery.

I find that if I unbolt the cable end and stuff it into a heavy plastic bag, I can prevent it making contact until I want it to.

dr bob

Adam -

Lift the ground strap where it bolts to the rear crossbar behind the tool panel. Wrap a plastic bag around the end of the cable to keep it isolated. Much easier than lifting the covers and pulling the spare out.

Some have added an isolation switch there. Needs a different (longer) ground cable and a bit of bracket to hold the switch. Good if you are in and out of the car regularly. Else lift the end of the strap and call it good.