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Re: bad battery or bad alternator ?
1) Check charging system for more than 13V off idle with accessories (heater
and lights) on. Less could indicate alternator problem. If the system holds
a charge briefly after simple jump start and driving, the alternator is
2) Consider a draw on the system with the key off, sapping an otherwise
serviceable battery. Disconnect negative battery terminal, connect amp
meter between negative terminal and battery post. With everything turned off
and doors closed normal allowable draw is no more than 50 MA. If less, than
that and charging OK, repl battery. Draw can be intermittent, common sources
of draw are antenna, door switches, window control relay, Mirror circuit
(broken wires crossing in driver's door jamb), fuse box cover was left loose
in the rain, trunk light left on (switch).
----- Original Message -----
Sent: Tuesday, August 17, 1999 5:01 PM
Subject: bad battery or bad alternator ?
> Scenario: '84 5000S sits for a number of weeks.
> I drive it around the block a few times.
> It sits another 3 weeks,
> Then it won't start, accompanied by warning chimes getting
> Jump-start (that isolation-surrounded post is really a good idea!),
> drive for about 30 minutes at town speeds.
> Car sits another week.
> Attempting to start, I get nothing again, and again the
> waring chime gets fainter with every second and with
> every turn of the key to Start.
> Knee-jerk reaction: must be a bad battery.
> Any (dis)agreement based on these symptoms?
> (I was about to try and find a new battery, when it occurred
> to me that somehow it might be a bad alternator. But the
> symptoms don't really fit, do they?)
> (BTW: Thanks to all who helped with the cooling fan mystery,
> which I will attack this weekend with a newly acquired Bentley,
> and also for the battery and Bentley sources)
> -G. Benedikt Rochow