Technical information

AUTOTRONIC CONTROLS CORPORATION • 1490 HENRY BRENNAN, EL PASO, TEXAS 79936 • [phone] • FAX [phone]
www.msdignition.com email: [e-mail]
82
MSD RPM ACTIVATED SWITCHES
NOT USED
GRAY
RED
WHITE
BLACK
YELLOW
TO GROUND
TO TACH TERMINAL
ON MSD OR
COIL (-) IF AN MSD
IGNITION IS NOT USED
TO SWITCHED 12V
+12 VOLTS
RPM
MODULE
PN 8950
AUTOTRONIC CONTROLS CORPORATION
1490 HENRY BRENNAN DR, EL PASO, TX 79936
TM
RPM
ACTIVATED
SWITCH
PN 7552
SHIFT LIGHT
RPM ACTIVATED SWITCH
TO A SHIFT LIGHT
This section covers the MSD RPM Activated Switch, PN 8950, and the Window Switch, PN 8956. The PN 8950 will
activate a circuit at a desired rpm by supplying or removing ground. The PN 8956 Window Switch will activate a
circuit by supplying ground, then will deactivate the same circuit at a different rpm.
The MSD Switches are capable of switching approximately 2 amps continuously. If too much current or the circuit
heats up over time, the Switches will shut off to prevent damage. For circuits that require more current for an
extended time, MSD recommends a Relay. Page 84 shows a relay wiring example.
If no module is installed, the switch will not activate.
An RPM Activated Switch for magnetos is also available as PN 8957. It shares the same wiring as the PN 8950.
Wire F unctions
Red: Connects to a switched 12 volt source.
Black: Connects to ground.
White: The rpm input wire that picks up engine rpm. It connects to the tach output terminal of an
MSD Ignition. When used with inductive or factory ignitions it connects to the coil negative
terminal.
Activation Wires:
Yellow: This wire is normally open and will switch to ground at your desired rpm to complete a circuit.
Gray: This is on the PN 8950 only. This wire is normally closed to ground and will open a circuit
at your desired rpm.
Cylinder Programming Loops: There are two wire loops, Red and Blue, on the side of the Control. For a 6-
cylinder engine, cut the Red loop. For 4-cylinder applications, cut the Blue and Red loops.