At 07:11 PM 10/22/2000 -0400, J R Overcash wrote:
>.... now has anyone added these little gems and how does one do it? ....
Let's start with the volt meter, because it's really simple to install.
You can use light gauge wire, because it only has to carry the tiny current
required to move the volt meter needle. In this case just attach one volt
meter wire to the switched side of the ignition switch (or any other wire
common with that terminal), and connect the other volt meter wire to any
good ground connection. If the needle on the volt meter moves toward lower
voltage when you switch on the ignition, then you need to swap the wires at
the back of the volt meter. As common safety practice, insulate (or
isolate) the wire terminals, and secure the wire so it doesn't thrash
around with vibration.
For the amp meter, start by finding where the primary battery cable enters
the engine compartment. It will attach to one of the following:
a.) Mechanical starter switch, used with pull to start
and bendix drive starter motors (MGA or earlier).
b.) Starter remote solenoid on inner fender, used with key start
and bendix drive starter motors (MGB -1967).
c.) On the starter motor, used with pre-engaging starter drive
With solenoid on the starter motor (MGB 1968-).
At that point you should find a heavy gauge brown wire that is feeding
power to everything in the car except the starter, and also carries the
charging current back to the battery(s). This heavy brown wire will go to
the control box (voltage regulator) in all cases, except when using an
alternator with built in regulator when this wire will terminate at the
alternator. For your common analog amp meter, you connect the amp meter in
series with this wire, using heavy gauge wire at least as large as the
original brown wire (or better yet one size larger to avoid voltage drop
with high current).
Disconnect this brown wire at either end (but be sure the charging current
still goes through the meter). Connect one of the amp meter wires to this
brown wire, and the other amp meter wire to the terminal from which it was
taken. There is much current involved here, so be sure to make a solid
splice that will hold up with time, and be sure to insulate it well and
secure it so it doesn't move and rub on anything. As these wires will
carry the full maximum charging current, they will not be fused. If any of
these heavy wires should ever short to ground, it would cause a dead short
for the battery, which would most likely cause a severe meltdown of the
wire insulation, and any other accompanying wires in the harness, and also
very likely cause a fire. If your amp meter needle moves towards "charge"
when you switch on the ignition (before starting the engine) you should
switch the wires at the back of the gauge.
If you are installing one of the inductive pickup type amp meters you can
use smaller wire similar to the voltmeter. In this case you attach the
inductive pickup unit around the heavy brown wire, and then connect the two
small wires for the gauge to the inductive unit. Again, if the gauge
needle moves towardds "charge" when you switch on the key you need to swap
the gauge wires. Most of these units require no other connection, but some
may require light current power and ground connections, in which case you
follow the instructions supplied with the gauge.
I personally do not like the analog type amp meter, simply becasue I don't
like having unfused heavy gauge high current wires routed up behind the
dash in the passenger compartment. If there should ever be a short in
these wires, and a meltdown and/or fire to ensue, I would much prefer to
keep the problem out of the passenger compartment. This is why I voted
$.10 for the volt meter and only $.05 for the amp meter.
Incidentally, I do like the idea of a digital volt meter pluged into the
cigarette lighter, except I can see possible problems maintaining a good
electrical connection if the lighter is actually used and the socket gets
cooked and dirty. As a matter of reliability I would still rather have a
digital volt meter hard wired.
$.02,
Barney Gaylord
1958 MGA with an attitude
http://www.ntsource.com/~barneymg
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