Battery drain E46 touring

[gareth.ireland3]

Hi have a parasitic drain on my car.checked all fuses in sleep mode.and nothing shows up on the multi meter.however just had a diagnostic done and it showed up a vehicle speed sensor fault.could this fault drain a battery t.i.a

[MauiM3Mania]

Moved from Car Audio and Electronics sub.

[shadowpuck]

no, a wheel speed sensor i don't think would keep the car from going to sleep.

how exactly did you perform your testing?

does the vehicle have any aftermarket components - stereos, etc?

[bmwdirtracer]

IF we assume that the electrical diagnostic for battery drain was done correctly by a good technician, then the alternative explanation is a bad battery. This is pretty easy to test. If the battery is charged to 12.6 or 12.7 volts after the car has been driven,, then the negative cable is disconnected, does the battery show 12.6 volts the next morning?

When the technician tested the battery drain, what was the actual drain figure, after the car was asleep? (It should be .035 amps, give or take .015 amps)

Was your testing done by an experienced BMW tech?

[MarcoZandrini]

The E46 has a common cause of parasitic drains: the final stage resistor (FSR). It’s used by the automatic climate control (IHKA) to vary the cabin fan’s speed.

How to check for a parasitic drain:
- disconnect the ground/earth/negative cable from the battery
- set up a digital volt/ohm meter to read amps
- connect one meter lead to the ground cable
- connect the other lead to the negative battery post
- allow the car to go to sleep (~15 minutes)
- the meter normally will read about 60 milliamperes (0.060 amps)
- start by pulling fuses 28, 62 and 63.

[jclausen]

if the blower fan is on for heater or ac, does the fan speed change on its own or when you select a speed does the fan not come on for right away those are also symptoms of faulty final stage unit.

[gareth.ireland3]

Will do that when off work thanks

- - - Updated - - -

I don't think so will check tonight

[gareth.ireland3]

I have replaced the old battery and I'm only getting a week out of it then I'm back to jump starting it .the mechanic that looked at the car for me said he couldn't find any drain on the battery when the car was in sleep mode .thanks for all your replies

[shadowpuck]

yeah, i'm guessing something wasn't done quite right on the test - as, killing a battery in a week should be a drain that could be found. i'd also wonder if the battery is actually being charged....

[gareth.ireland3]

I've had my alternator checked and it is charging the battery.ive been told that some aftermarket battery's aren't quite as good as an OEM battery.this is my first BMW so I'm not quite sure on what to do other that going to a dealer and have them look at it.which will cost an arm and a leg

[gareth.ireland3]

Hi again I've just checked the heater and the fan speed doesn't change straight away there's a few seconds before it speeds up

[bmwdirtracer]

Gareth, I am inclined to believe that you need a better BMW technician. I'd add that if the tech doesn't understand the dangers of amp-draw testing, he might have blown the fuse in his multimeter, and never known it. He said there's "no draw"....that is BS. there is ALWAYS a draw....your car has a clock, doesn't it?

If a top-quality multimeter with a 10Amp quick blow fuse is connected to the battery negative cable and battery negative post without buffering the sudden connection with a separate wire, it is VERY likely that the fuse in the multimeter will be blown, and the tech will read a ZERO draw. ZERO draw is impossible.

I have a box of these very special fuses for my Fluke multimeter....it's easy to overwhelm them, even using great care.