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Electrical: Engine Starting, Charging
Battery, Terminals, and Wiring:
Slow Battery Discharge. [Inquiry:] I am having an electrical problem with my
Volvo. About two months ago the battery went dead--slowly over time. It was an
old battery, so I though nothing of it and replaced it. All was good for a month and
a half, then it went dead again. With the car running I measured 14volts across the
terminals of the battery (12 when stopped) and 14v off the main positive lead of
the alternator. What is the problem here?
Resources. See this useful
[Battery Drain Diagnostics: Response: Ross Gunn] To check to see if there is
something draining the battery while the ignition key is removed, remove the
positive battery terminal, and with a digital electronics meter set to "amps",
measure to see if there is any current flowing between the battery terminal and
the cable end. For more accuracy, use a low-amp induction probe ammeter to
measure current flow through the battery cables. If there is anything more than a
couple of milliamps, re-connect the cable and remove fuses one at a time to see if
you can identify the circuit that is causing the drain. If this pins down a problem, a
little more sleuthing through the offending circuit should tell you what needs to be
done.
If there is no drain showing with the above test, the
Try measuring the voltage at the alternator output terminal and battery pos
terminal with all utilities (headlights, rear window heater, fan etc.) on high. Any
difference in reading indicates a poor connection somewhere in the red cable from
the alternator. Don't assume that a crimp connection of a terminal on the cable is
good. Corrosion can introduce enough resistance to prevent proper (any?) charging
when there is a significant load on the system (cold, dark, wet/snowy winter
evenings). I have experienced this on a 20 year old Brick.
[Battery Drain Diagnostics: Chris Bowne] I agree with Ross Gunn that the best
way to trouble shoot a discharging battery is to find the source with the engine
shut down and a multimeter (set to measure DC current) in series with the positive
battery terminal lead. Other places to check besides the fuse block for drain paths
are the alternator and voltage regulator (if not internal to the alternator).
Disconnect/reconnect the connections on them, one at a time, and monitor for
drain. I had a problem on a Ford Taurus once where the voltage regulator had
shorted, and was the cause of the drain. You may or may not find a source of a
drain like this merely by pulling fuses. In fact, you could end up with all the fuses
pulled, and still have the drain, like I did!
Someone on an earlier posting of this thread mentioned checking to see if his
alternator was providing output by lifting the battery + terminal connection WITH
THE ENGINE RUNNING. DO NOT DO THIS! Many solid state regulators will be
damaged/destroyed by this condition. (And in turn may compound the causes of
the battery drain you are troubleshooting!)
Battery Tips. [Tip from JohnB] Check the specific gravity of the cells...if they're
accessible. With a fully charged battery, either from your battery charger or the
alternator, disconnect the battery and measure the voltage, measure it again 12
file:///C|/Users/Steve/Documents/Volvo%20FAQ%20Updated/ElectricalStarting.html[01/13/14 10:02:47 PM]
site
for diagnostic ideas.
charging system
is suspect.
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