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Re: '86 5K qt charging system

-- [ From: human * EMC.Ver #2.5.02 ] --

>Have a son in San Diego with an electrical problem in his '86 5Kqt.
>About 3 months ago he replaced the battery and alternator because the
>battery was not retaining juice. Now the same thing is happening.

Respect to previous reply but the alternator (with v reg.) and battery are
probably not the problem - they've been replaced.  I would suspect a static
or dynamic leak.  To check for static (car not running, key out) disconnect
the battery ground and remake the connection with a test light in circuit. 
If you don't have a test light a turn signal or backup bulb works fine.  Now
any current draw will light the bulb.  Remove fuses to find out what is
drawing.  Expect the clock and radio memory to draw just a little but if the
bulb is bright at all you've probably got a "leak"

Dynamic is tougher to test for, because the car has to be running.  Try
measuring operating voltage at various points (alternator output, battery +,
fuse box, etc.  it should at least be over 13 volts.  14 would be nice but
these Bosch systems are a real pain, running barely enough voltage to keep
the system charging.  If you find drastically different voltages, it is
probably more than just series resistance.  I know this seems pretty vague,

Alternator function:  It must be grounded properly, by the mounting bolts. 
The small red (?) wire to the alternator carries +12v from the battery to
energize the stator field (electromagnet).  Check that wire for voltage. 
Then the output is the heavy wire(s).  Often this is two 8 gauge wires, one
to the battery and one to the fuse box (which then continues to the battery
yielding 4 ga from alt to batt).  If this wire is not carrying sufficient
current to the battery from the alternator then the battery slowly loses its
charge each time it starts the engine.  This might show up as a 13.5 volt
level at the battery with the engine running but nothing electrical turned
on, dropping below 12.6 v as you turn on all the accessories (hi beams and
heater blower are good current draws)

Check the quality of the load wire connectors at the alternator - they can

Hope this is of some help.
Huw Powell

82ish Coupe (drowned)
73 F250 (sounds like 4 Harleys)
various lawn ornaments (might be a redneck)

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