gauges at the dash are troublesome.
should be by-passed, and then install a VOLT gauge.
antiquated AMP gauge system has reduced more Dodge owners
to pedestrian status than any other kind!
(wire) “terminal illness” at firewall connectors has
also been a major problem.
Corp. stayed with the old AMP gauge system long after
other automakers switched to VOLT gauges, and Dodge trucks
used the AMP gauge more recently than others, so we have
used a Dodge truck as a model for this project.)
is not the only make with concerns about AMP gauge
systems, early FORD Broncos, International SCOUT, and many
old cars and trucks used the AMP gauge system too.
But when the electrical system will be up-graded
with more powerful alternators and more accessories, the
AMP gauge should be removed, and the “main power
system” should be modified.
With normal but frequent use, most of these Dodge
trucks will have electrical wiring problems.
The first to fail were often the trucks equipped
with factory air conditioning.
The air conditioning system adds a significant
electrical load. And
the “air” gets used in hot summer weather when heat
will increase resistance at connections.
The additional current flow when using the air
conditioning and increased resistance with heat will break
down the weak areas more quickly.
With sufficient use, the non-air equipped trucks
will also have electrical problems stemming from the same
Dodge electrical problems result from a very antiquated
power distribution system.
The main source of power for the Dodge electrical
system is based upon an old design AMP gauge at the dash
and related wiring system.
It’s a system that worked okay with a very small
electrical system on Model A Fords way back in the late
the old AMP-gauge-at-the-dash system is not reliable with
increased current loads of the more modern electrical
the situation, the wiring system for the AMP gauge
actually became weaker than it was over fifty years
line labor was not so expensive in early years of the car.
Affordable labor could consistently connect wires
with “ring terminals” at screws or studs with
nuts–resulting with reliable (low resistance)
connections. With increased labor cost mandating fast
moving assembly lines, and many more wiring circuits to
install, “click together” connections have been widely
used since back in the 1950’s.
And by the 1960’s, even the AMP gauge (heavy
current load circuit) was routed through a “click
The least reliable of “click together”
connections for a heavy current load circuit is the
male/female flat blade terminal design.
And it happens that Dodge was built with this
terminal design, even at the main power delivery circuit.
summary, the AMP gauge and related wiring found in Dodge
trucks of the sixties and seventies period was built with
a recipe for failure.
A 70amp alternator supporting powerful electrical
accessories was typical equipment by 1979, and the load
was too much for the method of wiring construction used.
Naturally, it’s a system that often reduced Dodge
owners to pedestrian status.
This feature clearly explains the shortcomings of
using the old, traditional, AMP gauge at the dash.
And largely because of the circuit design
shortcomings, the best choice of gauge to monitor the
electrical system is a “VOLT” rather than AMP gauge.
A good explanation of the AMP vs. VOLT gauge may be
found at www.autometer.com
in the Tech Tips / FAQ section of the web sight.
In some ways, the Chrysler Corporation was pretty far advanced
where electrical systems were concerned. (Chrysler gave us the Dodge, Plymouth and Chrysler line, and
nowadays they all may be referred to as MOPAR.) Back in the early ‘60’s, MOPAR was the first to give us
alternators rather than the older technology
generators–Indeed the improvement was great.
GM followed, and then Ford finally installed
alternators as “standard equipment” on ’65 models.
year model Chrysler products showed up with “Fusible
Link wires” for reliable short-circuit protection of the
main power circuit from the battery to the electrical
didn’t use Fusible Link wires until ’66 models.
Ford didn’t use Fusible Links until some years after GM.
introduced a very good electronic ignition system with
1971 models. Ford
introduced a somewhat less reliable electronic ignition
with only some of their ’74 models.
And GM gave us a very good electronic ignition with
spite of being the first to give us “break through”
technology with components, it seems that the “DODGE
BOYS” were reluctant to depart from a very antiquated
wiring system. The
old, traditional, “full current load type”
AMP-GAUGE-AT-THE-DASH and related wiring system was still
in use with ’79 Dodge trucks.
The AMP gauge circuit wiring had to deliver
electrical current used by the entire electrical system,
plus handle current to recharge the battery.
The problem was that current load and the
alternator output rating was a large amount by the end of
the ‘70’s. Alternators
with about a seventy amp available output were standard
with air-conditioned models.
And a weak terminal design was used where the AMP
gauge wiring passed through the firewall. The large demand for electrical current often resulted with
failures in the lengthy AMP gauge circuit, even in
vehicles that were relatively new.
original AMP gauge system served as the main power
This circuit is the power source for the entire
electrical system. (see
gauges at the dash were standard equipment with Model A
Fords, back in the late 1920’s.
And the fifteen amp capacity gauge at the dash
worked fine with minimal electrical systems of that
output from the small Model A generators was not even
sufficient to support sealed beam headlights.
(The old Model A was equipped with a small light
bulb backed up by a large reflector in the headlight
Model A only had one tail/brake light at the rear, a
simple ignition system and a small battery about completed
the electrical system.
Such a small amount of electrical current flow
through good connections at the AMP gauge wiring was no
problem with the Model A Ford.
And with current output limited by a cutout relay
on the generator, the AMP gauge could handle the small
battery charge rate.
But as electrical systems became more powerful,
Ford discontinued the old AMP gauge system long before the
also up-graded their system long before the Dodge Boys.
When GM introduced the alternator with ’63
models, it was controlled by a more complicated but more
efficient voltage regulator system.
And the new GM system could support a warning light
at the dash. The
warning light was often standard equipment and the gauge
was an option. GM vehicles built with the gauge option
also had a more modern design of AMP gauge at the dash.
The newer AMP gauge was a remote shunt type
design–a length of the battery charging wire in the
under-hood harness served as the shunt.
The dash gauge and related wiring no longer handled
heavy current load. Same
with Ford in ’65 and newer model cars–the Ford system
could work with a warning light at the dash, and cars that
came dash gauges had a remote shunt type amp gauge.
Dodge alternator/voltage regulator system
no provision to operate a warning light.
And Dodge (trucks) stuck with the old antiquated
“full load type” AMP gauge design, at least into the
late 1980 models. As
is typical of Dodge trucks that were used a lot, the AMP
gauge in this ’76 Dodge was burned out.
The plastic mounting area behind the dash is
completely melted, and the lens and plastic trim is
shriveled too. (This
gauge is included in Diagram A.)
is a measure of current flow, and all of the current used
to recharge the battery was routed through this
gauge–which caused the gauge to display the battery
charge rate. Both
the alternator and the battery were mounted up front,
under the hood. And
the AMP gauge was at the dash.
It was an arrangement resulting with a very long
wire circuit charging the battery.
amounts of current flow through the AMP gauge will
generate some heat too.
The plastic cover at this gauge was only distorted
by heat–but some Dodges have sizable holes burned in the
dash where the AMP gauge used to be.
Apparently, the shunt in the gauge has a sufficient
amount of resistance to generate a damaging amount of heat
with battery charging current flow.
A previous owner had replaced the terminals at the
back of the AMP gauge, and then did a weak by-pass of the
gauge by taping the two wire terminals together.
(No doubt an attempt to get the old Dodge up and
It’s fairly common to find the wires disconnected
from the gauge, and a machine screw and nut clamping the
terminals together, and finished by wrapping the screw and
terminals with tape.
The AMP gauge wiring passed
through the “firewall bulkhead connector,” where
standard, .250 inch wide, male/female flat blade
connectors were used.
(This connection is shown in Diagram A.)
These terminals were reliable with circuits of much
less current flow, as with turn signal, clearance lights,
and temp or fuel gauges.
But the design was certainly not up to the job of
handling the entire alternator output.
This was a problem spot in the AMP gauge system
that often made Dodge owners walk.
A in the photo at the left points out a
melted cavity in the plastic connector body, where a case
of “terminal meltdown” occurred.
This connection served as a pass-through for the
main wire from the alternator to the dash area.
When driving, the entire electrical system current
load will pass through this connector.
(Also seen in Diagram A.)
Ignition, lighting, heater fan, accessories, and
electrical power in general flows through the connector.
The wire color code is black at this circuit, and this
model was equipped with 10 gauge wire.
(Many earlier models had only a 12 gauge black
points out the red, 10 gauge, battery charging wire.
removing the connector with the red 10 gauge battery
charging wire, a close inspection revealed that this side
of the AMP gauge circuit was also suffering from a case of
(See arrow in photo at the left.
This is the terminal used by the 10 gauge red wire
at arrow “B,” above.))
plastic connector body surrounding the female flat blade
terminal is beginning to melt away.
And severe oxidation of the terminal itself is
evidence that this terminal has been glowing hot.
Notice that the other terminals in the connector
body are still in good condition.
The rusty appearance of this terminal is typical of
wire terminals that have been hot while handling large
amounts of current flow.
(If moisture had caused the oxidation, all the
terminals would have been corroded.)
We have opened part of the dash wire harness, to
show the factory “welded splice” where wires branch
off to the ignition switch, light switch, and the fuse
(This splice is shown in Diagram A.)
The “welded splice” is insulated by a factory
installed, sticky cloth tape.
original tape has been removed for this photo to expose
the “welded spice.”
and heat fused the copper wire strands together when
making the splice. The
method seems to be reliable, as in thirty years of
workshop experience the author has never seen a failure
with this splice. When
electrical power loss occurs, this is certainly not the
first place to look for the problem.
here to see Part 2,
where we will by-pass the gauge and repair the wiring