Technical information

AUTOTRONIC CONTROLS CORPORATION • 1490 HENRY BRENNAN, EL PASO, TEXAS 79936 • [phone] • FAX [phone]
www.msdignition.com email: [e-mail]
120
Note #2 Tach Manufacturers
Auto manufacturers use tachometers made by different tachometer manufacturers. Some will work when con-
nected to the MSD Ignition Unit Tach Output Terminal, others may require an MSD Tach Adapter. Connect the
tachometer trigger wire to the Tach Output Terminal of the MSD to determine if the tachometer is operating
correctly. If it does not operate correctly, go back to the chart to determine which MSD Tach Adapter should be
used. See the chart on page 119.
TACHOMETER INFORMATION
Note #1 Tachometer Types
There are basically two types of tachometers: Current Triggered Tachometers and Voltage Triggered Tachometers.
The type of tachometer that is on the vehicle may be recognized by the way it is connected to the ignition coil. The
drawings below show two wiring diagrams to help in determining which type of tachometer is on the vehicle.
This diagram shows a typical wiring schematic for
aftermarket tachometers. These tachometers will
usually have three wires and sometimes a fourth for a
panel light. The tach trigger wire is the wire that origi-
nally went from the Tachometer to the Negative side of
the coil. With an MSD installed, remove the wire that is
connected to the coil negative terminal and connect it to
the MSD Tach Output Terminal as shown.
Tachometer Trigger Wire
NOTES
Current Triggered Tach Voltage Triggered Tach