From: Richard (metal@fullwave.com)
Date: Wed Apr 23 2003 - 16:36:12 PDT
Many older trucks and cars, and heavy equip.,
were positive ground.
I always change them over to 12v neg. ground.
the starter will still work fine, i.e. same direction.
it's a series-wound motor.
the gen/reg would need to be replaced.
63 or 85 amp Delco alt's with built-in regs are
only 30 bucks at my local napa, so that's what
i put in everything. good basic alt, easy to repair
too.
note; many modern alt's sense the batt voltage via
the same wire that the charging current goes thru!
often called "single wire" alternators.
in other words, voltage-drop across that wire, due
to the charging current, will fool the built-in reg
into thinking that the batt voltage is fully up, even
when it ain't! The problem is worsened by long
runs back and forth from an ammeter. It's a good
idea to use the heaviest possible wire between alt
and batt. I usually use 4 gauge, or even a pair of
4's.
The delco's i get are the type with 2 extra wires
coming out on a plug. one of those wires is the
'sense' wire; which you run direct to the on/acc
position of the ign. switch. that gives the built-in
reg an accurate view of the system voltage.
the other wire normally goes through the 'alt'
idiot-light on the dash. you can run that through
a resistor of a few ohms, to the on/acc position.
or just use an idiot-light bulb <g>. in any case,
it -does- have to be hooked up for the alt to work
reliably. otherwise, it'll charge sometimes, but
not other times. all depends on whether the armature
was magnetized at the moment you last shut it
off.
there's almost nothing else in an old rig that's
polarity-sensitive. watch out for radios tho...
also, the 6v starters work fine on 12v, so long
as you aren't cranking them all day. most people
with older cats use an 8v batt, and tweak the 6v
regulator to charge it. the starter spins a tiny
bit quicker; which helps those old pony motors
get going. when either the gen or reg on a 6v
cat goes bad, some people just disconnect the
charging system, put in a 12v batt, and charge
it off their yard-truck once a week. doesn't seem
to hurt the starter at all.
anyway, if you change it to neg-ground, you'll
probably never make a (possibly dangerous)
mistake with jumper cables; you can run all
your modern radio gear in it without endless
headaches; and every electrical accessory
at napa will work fine....along with elec. fuel
pumps etc.. which is nice...<g>
Richard
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