Subject: RE: new wiring diagram (long)
Author: Tom Bowes
Date: Feb 10, 2001, 6:02 PM
Post ID: 1705375846
Ian Adkins wrote:
| Is there a disadvantage to using 12 ga for all the wiring...other than price...and likely stiffer wire? |
There is one huge disadvantage to using 12 gauge for everything and that
is that the size of your wiring harness will border on enormous. It is
unlikely that you would even be able to cram all the wiring into the
headlight bucket. As an electrician I have fought the wire size battle
enough times to know that bigger is not always better. Keep in mind that
an insulated number 12 AWG wire in open air is capable of carrying 35
amps which is more than the bike's generator (but not the battery!) is
able to deliver. Generally, in a building installation, #12 is limited
to 20 amps, #14 to 15, and #10 to 30 amps (this is per the National
Electrical Code), but that is because the conductors are run inside of
conduits or cables which limit their ability to dissipate heat.
On a bike the wires are hanging out there in the air and are much better
able to get rid of the heat created by the current flowing through them.
Dave is correct in stating that #12 is a good size for delivering power
from the battery to the power distribution block, but I would hesitate
to use it for much else. Keep in mind that even a lowly #18 wire is good
for 14 amps, according to the NEC.
Let's say that you were to rewire your cycle and upgrade the headlight
to one of the new H-4 100 watt jobs. This would likely be the largest
load on the system, with the exception of the starter. Using Ohm's Law,
you would find that the current draw from the headlight will be about
8.3 amps, easily within the 14 amp rating of an 18 AWG conductor. In
fact, an examination of my old wiring harness shows that this is the
size most preferred by Guzzi for nearly everything on the machine. (Of
course, they use the metric equvalent, which is a .75mm.) The only
wiring on the bike that NEEDS to be larger than #18 is the feed from the
generator to the fuse block, the wire from the fuse block to the
battery, and the starter power and solenoid wires. Does this mean that I
would feed a 100 watt headlamp with #18 wire? No, I would probably use
the good old "fudge factor" and go with a #16 for that particular load.
Nearly everything else; horn, turn signals, tailight, ignition, and
indicator lights could be done with #18.
The big problem with Guzzis is not with the size of the wiring, but with
the type of electrical connectors chosen for the majority of the
electrical loads. (And the infamously cheesy CEV switches). On my
machine the main wiring terminal block has a couple of connections that
have changed position because of the (not really) heavy current drawn by
the headlight, which caused the plastic surrounding the connections to
melt. Needless to say, if the connections couldn't hold up to the 4.5
amps of current drawn by the old sealed beams, they are not going to
fare well if I upgrade to a new headlamp that draws 8 amps plus.
Consequently, I will be changing out the fuse block to the newer ATO
style when I redo my harness!
My years of experience as an electrician and as an amateur radio
operator have taught me the value of making solid electrical
connections. The problem is that most of the connectors available on the
market at places like auto parts stores are J U N K. In the US (and
probably Canada) there are three manufacturers of electrical termination
connectors that I would trust. They are, in descending order, T&B,
Burndy, and Panduit. (OK, 3M has a few decent terminals also.) Even with
these I make it a point to buy the terminals WITHOUT the little yellow,
blue, or red insulating sleeves; opting to slide a bit of heat shrink
tubing over the completed crimp connection. If I want a REALLY long
lasting connection, I crimp and then solder them with a good rosin core
solder. But then again, my electrical connections, like my
dissertations, tend to go to extremes.
Tom
'70 Ambassador
'82 V50-III
Shelby Township, Michigan