Dakota Digital VFD3 Installation And Operation Manual page 8

SPEED
The vehicle speed sensor (VSS) connects to this to tell the system how fast the vehicle is
moving. For two wire speed sensors, like the one Dakota Digital supplies with this system, the
polarity of the wires does not matter. Connect one wire to ground and the other to the speed
terminal. The speed sensor ground wire should be brought back to the control box to ensure a
proper signal is received. Twisting the ground and signal wires around each other provides an
additional level of interference protection. The speed signal wire should not be routed along
side ignition or other high current or high voltage wires.
For vehicles which already have a vehicle speed signal, tap into the VSS wire and
connect it to the speed terminal. You may have to consult a vehicle service manual or wiring
diagram to determine wire color and location.
This system can accept 4000 ppm – 128000 ppm speed signals. The sensor that Dakota
Digital provides is an 8000 ppm type. The speedometer is fully adjustable and calibration is
discussed in a later section. Failure to calibrate the speedometer may cause your
odometer mileage to increase very rapidly if the speedometer is reading too fast.
TACH
Depending on the type of system that you have there may be a bar graph tachometer, a
digital tachometer, or both. Connect the tach terminal to the ignition system. On vehicles using
a separate ignition coil, connect to the negative side of the coil. The negative side of the coil will
be the wire that goes to the points or electronic ignition module. For GM HEI ignition equipped
motors, connect to the terminal marked "TACH" or on some systems, to a single white wire with
a spade terminal on it. On MSD ignition systems, connect to the TACH output terminal. On
computer controlled ignition systems consult a service manual for the wire color and location.
GM LS1 engines require the tach to be set up for a 4 cylinder, low voltage signal. With magneto
system connect to the kill wire for the tach signal. Do not connect the TACH terminal to the
secondary, or high voltage side, of the ignition coil. To ensure that the ignition system does not
interfere with any other dashboard functions, do not run the tachometer wire along side any
other sender or input wires. DO NOT USE SOLID CORE SPARK PLUG WIRES WITH THIS
DASHBOARD SYSTEM. Solid core ignition wires cause a large amount of electromagnetic and
radio frequency interference which can disrupt the system operation.
The tachometer is compatible with almost all gasoline engines. The engine cylinder
selection, display update rate, tach signal type, and rpm warning point can be adjusted in the
setup menu under "TACH". If a diesel engine is being used then you will need a tach interface,
such as Dakota Digital's DSL-1 or DSL-2.
WATER
The water temperature sender included with this system must be used. Other senders
will cause incorrect readings. The sender mounts on the engine block or into the intake
manifold so that the end of the sensor is in the engine coolant flow. The sender gets its
electrical ground connection to the engine block through its threads. Do not use Teflon tape or
thread sealant on the sender threads. Doing so can cause incorrect readings or cause the
gauge to display an out of range indication. A sender with 1/8 NPT thread size is normally
included along with adapters to go to 1/4, 3/8, and ½ NPT. If the engine you have requires a
metric or non-standard thread size you can contact Dakota Digital for availability or check your
local auto parts dealer or hardware store for an adapter.
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