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Postive / Negative ground system
09-17-2005, 13:42
Post: #2
Postive / Negative ground system
Sounds like they are both negative ground systems. The
"ground" of a system is determined by which terminal
of the battery is connected to the frame/body/engine.
So in a negative ground system, the negative side of
the battery is connected to the frame, and all
positive connections must be isolated from the frame.

Notice that one alternator has the 3rd wire positive
to positive, the other has the third wire negative to
negative. No problem there. Does the 2nd alternator
have anything connected to the positive connection?

Scott Peatross
'87 PT40

--- transit360 wrote:


---------------------------------
I have two Bluebird QBRE's and they are wired a
little diffently.
In short, how can I tell if someone has wired one bus
or the other
for a positive or negative ground system? Please only
advise if you
can supply me with some tests I can run with a meter
or if you've
had experience with electrical systems. I'm running
inverters and
they've warned NOT to use these with a positive ground
system.
The reason I ask is because there is a + and -
terminal on the
battery hooked likewise to the alternator. Then I have
a 3rd wire,
probably 6 gauge that runs to the starter.
NOW, on the 1st bus this 3rd wire runs from the
+ on the
alternator to the starter SOLENOID, where is shares a
main + feed
from the battery.
On the 2nd bus, this same wire runs from the -
side of the
alternator to a ground stud of the back of the starter
BODY, where
is shares this stud with a main ground strap. Is this
a postive
ground system?
I only discovered this after on the 2nd bus I
hooked this
wire to the + side of the alternator to match the
other bus, only to
have it heat up. I didn't know why until I traced the
wire to the
ground stud on the starter body.
Would anyone know of any reason why a mechanic
would do this,
especially on two identical buses? And more
importantly, how can I
wire this system up to guarantee that it's the typical
negative
ground system that I need? Or is this system still a
negative ground
anyways?? I have a little electrical knowledge but I'm
stumped and I
really don't want to damage my new inverters.

Thanks,
Steve
Two '98 Bluebird QBRE Partybuses





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Messages In This Thread
Postive / Negative ground system - transit360 - 09-17-2005, 07:38
Postive / Negative ground system - Scott Peatross - 09-17-2005 13:42
Postive / Negative ground system - steve wicker - 09-17-2005, 20:01
Postive / Negative ground system - bluebirdsp36 - 09-18-2005, 07:57
Postive / Negative ground system - Tom Warner - 09-18-2005, 12:03
Postive / Negative ground system - steve wicker - 09-19-2005, 04:03



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