I am having an issue with battery being dead after about 4 days sitting. I tested the battery at teh local parts store and it tests OK. It's only about 6months old anyhow. So this morning I do a IOD test on the car. Immediately after you shut the car off, the draw is about 1.7amps. Over the next two muinutes as things shut down the current drops to it's final .38amps.
I have read about the seat modules killing the battery so I disconnected them completely. Still sitting at .38 amps.

So, What should my IOD be on this car? One thing I did not check was the draw with the alarm activated.

-J

 

IMHO .38 amps of parasitic current draw is quite high.

While many of the electronics (e.g. radio, clock, control modules etc.) have 'keep alive memory' requirements, the current draw of each is low, typically a few milliamps, so the total current draw might be 10 - 40 milliamps. Note: a milliamp is one thousandth of an ampere, so 40 milliamps would read as .040 amps on your meter.

With your measured parasitic draw of .38 amps, over a 4 day period, the battery would have to provide 36 amps of current (e.g. .38 amps x 24 x 4), which would be quite demanding. While demanding, a new fully charged battery should not die in 4 days.

Since your battery dies in 4 days, check to to be sure that your alternator/voltage regulator are operating properly and charging the battery to it's full capacity.

If that checks out, the next step is to isolate the circuit responsible for the high current draw. You can do this by disconnecting the negative battery cable and connecting an amp meter in series, between the cable and battery post. Next, begin pulling fuses, one by one, to find the circuit responsible for the high current draw. By isolating the circuit, you will greatly narrow down the problem area. Then you can disconnect potential modules, look for short circuits etc. Hint: Even circuits that normally do not contribute to parasitic current draw, do so via unattended short circuits. For example, even something like a dome, trunk, glove box bulb etc., that is normally switched off, but remains on via a stuck/faulty switch can draw considerable current. Current = power / voltage, so even a 3 watt bulb, always on, will draw .25 amps (e.g. 3 watts / 12 volts = .25 amps).

Now I'm wondering if the light bulb, inside my refrigerator, turns off when I close the door.

 

would you be able to check yours and let me know what a normal off draw is?
thanks!
-J

 

No need to. If the ammeter is reading over 25-50 milliamps, something is using too much battery power when the car if off.

Enclosed is a WIS that indicates what the W208 'maximum' parasitic current draw is when the car is turned off.

Off means key out of the ignition. Additionally, immediately after the car is turned off, the current draw will be much higher, due to time delay circuitry that needs to end.

At this time you need to follow the trouble shooting steps outlined above.

By pulling fuses to find the fused circuit responsible for your parasitic current, you can then trouble shoot the problem to a one of the devices that runs off this circuit.

Checking that the alternator / voltage regulator is functioning properly not only insures that your battery is being fully charged, but the charging system can sometimes have a shorted diode, that can cause parasitic current to flow through a shorted diode.

 

Pulled every fuse in teh car and tested current draw today. The only significant decrease in current came with the removal of fuse 12 in the engine bay. dropped from .38 to .1 AMPs. quite a drop for sure, but still well above the 40 milliapms recommended.

Fuse 12 is labeled soundsystem. Guess I have some research to do. The radio is aftermarket, but I''ve had the same problem with the previous unit, also aftermarket. I'm probably going to check the draw when I physically disconnect the amp.

 

The rear of the factory head unit has 5 ports. Port labeled #2 is two rows of four pins. The lower right hand pin of the second port is typically hot. Thats why you can turn the radio on in a car with the OE head unit. If you are using that pin for anything, that could be the problem.

 

found it.
I have a PAC SOEM-4 unit to line match the speaker voltage from the aftermarket head unit to the Bose AMP. The PAC unit takes constant 12v in and a remote amp turn on. There is 1.5v leakage on the remote line coming from the PAC device. This was enough to keep the Bose amp on all the time. Cut the remote turn on on the PAC device and I get 100mA draw. So... I think I will try putting the PAC device on a switched 12v input. This will solve that issue, but I may end up with a pop when the car is turned on. We'll see...
-J