Technical information

AUTOTRONIC CONTROLS CORPORATION • 1490 HENRY BRENNAN, EL PASO, TEXAS 79936 • [phone] • FAX [phone]
www.msdignition.com email: [e-mail]
94
3-STAGE RETARD, PN 8970, AND
MULTI-STEP RETARD, PN 8972
Red:
Black:
Yellow:
Connects to switched 12 volt source.
Connects to ground.
This is the trigger output to the Ignition. It will connect to the MSD’s White wire or Points
terminal.
White:
Violet and Green:
Connects to points or an ignition amplifier output. When this wire is used the Magnetic
Pickup is not (Violet and Green).
These wires are routed together in one harness and form the magnetic pickup connector.
This connector plugs directly into an MSD Distributor or Crank Trigger. The Violet wire is
positive (+) and the Green wire is negative (-). When this connector is used, the White wire
is not and should be sealed.
General Wiring
Trigger Wires
The 3-Stage Retard, PN 8970, supercedes the Multi-Step Retard, PN 8972. They both are designed to provide up
to three different retard rates that can be activated at different times. The three stages are cumulative up to 20° (6°
on first stage, 4° second, 2° third means 12° total).
There are three retard module sockets on the side of the unit, each with their own activation wire. Each stage is
activated when the corresponding wire is removed from ground. If a stage is not going to be used, its activation wire
MUST be connected to ground, or a Zero degree rpm module MUST be installed.
Activation Wires
Start Retard
Brown:
Orange:
Gray:
When removed from ground, the FIRST stage is activated.
When removed from ground, the SECOND stage is activated.
When removed from ground, the THIRD stage is activated.
Note: If a stage is not going to be used, the wire should be grounded or a Zero degree module must be installed.
Violet:
Violet Loop:
Activates the start retard when supplied with 12 volts. The PN 8970 will automatically
deactivate the retard once the engine reaches over 1300 rpm and will not return again until
the ignition is turned Off or engine rpm drops below 400 rpm. The PN 8972 requires
momentary 12 volts to activate and will deactivate when 12 Volts are removed.
Under the cover next to the Blue and Red cylinder loops is a Violet loop. This adjusts the
start retard of the PN 8970 only. When it is not cut, the retard is 10°, cutting it will retard it 25°.
Cylinder Select: There are two wire loops under the small cover on the side of the control. For 6-cylinder operation,
cut the Red loop, for 4-cylinder engines, cut both the Red and Blue loop. See page 91.