RE: <E36> Battery drains

[alex.fadeev@xxxxxxxxxxx]

Bob A. Virzi/EMPL/MA/Verizon@VZNotes wrote:
> Problem:  If the car sits for any extended period of time (2 - 4
> days) without running, the battery is too weak to start the car.
> Not quite dead, but not enough juice to start, either.
> Background:  We have had an ongoing problem in my wife's 318 since
> we got it in '97.  She always runs a radar detector which stays on
> even when the car is off.

Bob,
How is that detector wired?
There are plenty of V1 hard-wiring instruction on the net on how to wire it
to the 'hot only when ignition is on' sources. Much more convinient and
better both for the detector and your car's battery.

> She used to also keep her cell phone plugged in and charging,
> but no longer does so.  We are on the third, maybe fourth, battery.

Ahem, no kidding!

> The dealer is claiming the detector is killing the battery.

Unlikely, but not impossible. What detector do you have an how much power
does it draw?
Either way, you should re-wire it to come on only with ignition.

What replacement battery are you using? Is it up to the job of running your
car in the first place?
When was the last time you checked the battery fluid level?

> Especially as the battery is weakened with age (like about a year)
> it is being dragged down by the detector until it is dead.  Claims
> that BMWs are more sensitive to battery level than other cars. Also
> has checked the car several times and claims there isn't any other
> drain when the detector is disconnected.

That's not true. There _is_ a noticable draw on the battery from all the
electrical gizmos that must keep memory. DME, OBC, Radio, clock pop to
mind. I'm sure there are plenty more. But unless one of them is shorted,
the draw should be minimal and take weeks, if not months, to draw the
battery down.
Something else is eating your battery. Could be the detector. Could be
something else.

> So this sounds like pure cr*p to me.  I've run detectors in at least
> a dozen cars and never had a problem like this.  We're talking
> milliamps of current.  Has anyone else experienced a problem like
> this?  Maybe the alternator isn't putting out what it should?  Other
> ideas?

1. Rewire the detector.
2. Until you do, unplug it and see if that battery drains without it.
3. Put a voltage meter in line with the battery and start pulling the
fuses. Note the drop in draw with each fuse. Cross reference with the E36
Bentley (you do have it, www.rb.com, don't you?) to see what electrical
gizmos hang off that fuse.

>  I hate to add a battery a year to the maintenance schedule.
> ;-)

You absolutely should not!

hope this helps,
alex f

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