MSD 6421 6AL-2 Ignition Control Installation - Manual (Page 4)

4 INSTALLATION INSTRUCTIONS
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WIRING
GENERAL WIRING INFORMATION
Wire Length: All of the wires of the MSD Ignition may be shortened as long as quality connectors
are used or soldered in place. To lengthen the wires, use one size bigger gauge wire (12 gauge for
the power leads and 16 gauge for the other wires) with the proper connections. All connections must
be soldered and sealed.
These are the two heavy 14 gauge wires and are responsible for
getting direct battery voltage to the ignition. The Ignition is load
protected from reverse battery connections and will automatically
shut down if there is over 28 volts input.
This wire connects directly to the battery positive (+) terminal or a
positive battery junction such as the starter solenoid. Note: Do not
connect to the alternator.
This wire connects to a good ground, either at the battery negative
(-) terminal or to the engine.
Power Leads
Heavy Red
Heavy Black
Accessories
Blue
Gray
Red
Orange
Black
Trigger
Wires
White
White/Blue
Violet
and Green
(Magnetic
Pickup
Connector)
This wire is responsible for turning the MSD On and Off. Connects to
a switched 12 volt source such as the ignition key or switch.
This wire connects to the coil positive (+) terminal. This is the
ONLY
wire that makes electrical contact with the positive coil terminal.
This wire connects to the coil negative (-) terminal. This is the
ONLY
wire that makes electrical contact with the negative coil terminal.
There are three circuits that can be used to trigger the MSD Ignition;
a Points circuit (the White wire), a Magnetic Pickup circuit (the Green
and Violet wires), and a Hall-effect wire (White/Blue). Only one circuit
will be used at a time.
This wire is used to connect to breaker points, electronic ignition
amplifier output or to the Yellow wire of an MSD Timing Accessory.
When this wire is used, the White/Blue wire and Magnetic Pickup
connector are not used.
Hall-effect Trigger. This wire connects to the trigger wire of a Hall-
effect pickup. When used, the White and Magnetic Pickup wires
are not used.
These wires are routed together in one harness as the magnetic pickup
connector. The connector plugs directly into an MSD distributor or
crank trigger. It will also connect to aftermarket pickups. The Violet
wire is positive (+) and the Green wire is negative (-). When these
wires are used, the White or White/Blue wires are not.
This wire activates the Two Step Rev Control. When 12 volts is applied
to this wire, the low rpm limit is activated. When 12 volts is removed,
the rev limit returns to the high limit.
Tach output wire. Connects to the tachometer trigger wire or other
rpm activated device.