'97 SL2 draining battery

I have a 1997 SL2 Saturn that will drain the battery after two days of no
operation. I have had the battery and the alternator tested and they were
ok. I'm assuming that there is an electrical leak somewhere in the car. Is
this a known problem? How do I go about finding where the battery is being
drained?

TIA

 

Disconnect the Positive battery cable and install a (milli)ammeter in series
with the battery post. Set to highest current setting, turn off all
accessories and leave the ignition off. Close all vehicle doors, etc. so
all lights, etc. go off. After everything goes off, switch current scale to
lower setting as needed to measure actual current drawn. There should be
negligible current drawn from the battery, probably less than 20-30mA for
the keep alive circuits (clock, alarm, etc.). Someone with a service manual
could probably give you the actual number here, but 25mA is probably about
right. If the current you measure being drawn is much higher (sounds like
it will be), then you should start pulling and replacing fuses to see which
circuit is causing the excessive draw. This should at least point you in
the right direction.

Good luck and post what you find for the benefit of others.

Bob

 

On disconnecting the battery -- there was a brief discussion on Car Talk
recently about the order in which to remove the battery connections. It
is wisest to remove the negative before the positive since the car is
grounded to negative. If you go straight in to disconnect the hot
positive terminal, you risk shorting the battery if your
wrench/screwdriver happens to brush too close to any metal on the
car/engine. So if you want to put an ammeter in, maybe you should go to
the negative terminal instead of the positive.

Alternatively, if you have small enough probes on your multimter/ammeter
(or just connect some small gauge wire to each probe), you may be able to
go to the fuse box and measure the current of each circuit directly (i.e.,
pull a fuse, touch the probes to the terminals where the fuse was, and see
what the current flow is; repeat for each fuse).

 

Is this the original battery? If so, it is probably time for a new one...
Seven years is really good for a battery.

When they tested your battery they didn't test how long it held a charge
past a few minutes, did they? Did they measure the internal resistance
under both charge and discharge or just hook it up to a go/no-go meter?

To measure the drain, put an ammeter between the battery's negative cable and
the negative battery terminal. If you see a drain there,
you can start pulling Maxifuses
to find which major circuit has the drain, and then the corresponding mini-
fuses to find the exact device.

Tim.