MSD 8950 Installation

MSD RPM Activated Switch

PN 8950

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IMPORTANT: Read the instructions before attempting the installation.

Parts Included:

1 - RPM Switch 4 - Heat-Shrink Caps
4 - Self Tapping Screws

Note: RPM Modules must be purchased separately. See the chart on the last page for part numbers.

The RPM Activated Switch can be connected to stock ignition systems or MSD Ignitions. When using a
capacitive discharge ignition such as an MSD, do not connect the Switch to the coil negative terminal.
Damage to the Switch may occur.

The Switch is capable of carrying 1.5 amps. If the circuit you are activating requires more current,
an MSD Relay, PN 8960 or 8961 must be used. The MSD RPM Activated Switch is equipped with a
"smart driver". This circuit will protect the RPM Switch from damage by monitoring its temperature.
If there is an inadvertant short or too much current is drawn through the Switch, the smart driver will
sense the increased temperature and shut the Switch off. However, once the temperature drops to a
safe point, the smart driver will turn the Switch back on. It will continuously cycle On and Off as the
temperature dictates.

If you experience a problem with your Switch not operating, turn the circuit off for a few minutes to cool,
then try again. If the circuit activates then shuts off, there may be too much current flow. Check the
device's Installation Instructions to find its recommended maximum current.

The RPM Switch has two activation wires. The Yellow wire is Normally Open and will activate a circuit
by switching to ground. The Gray wire is Normally Closed to ground and will open the ground circuit
at the desired RPM (Figure 1). If no rpm module is installed, the Switch will not activate the circuit.

Figure 1 Operation of the RPM Activated Switch.

M S D   •   W W W . M S D P E R F O R M A N C E . C O M   •   ( 9 1 5 )   8 5 7 - 5 2 0 0   •   F A X   ( 9 1 5 )   8 5 7 - 3 3 4 4

2 INSTALLATION INSTRUCTIONS

SEAL THE LOOP ENDS

HEAT-SHRINK

CAP

CYLINDER LOOP

CYLINDER PROGRAMMING

The Switch is programmed for 8-cylinder applications, however it can be used with 4 or 6-cylinder
applications. To program the Switch for different applications, the cylinder select loops must be modified
as shown in Figure 2. After cutting a wire loop, seal the wire end with the supplied heat-shrink caps.
Use a heat gun or other heat source to shrink the cap for a good seal.

CYLINDERS CUT LOOPS

8 NONE
6 RED
4 RED & BLUE

RED

BLUE

Figure 2 Cylinder Select Loops.

MOUNTING

The Switch may be mounted under the hood as long as it is away from direct engine heat sources.
Keep in mind that the rpm modules should be easy to access for changes. The Switch can be mounted
with the double-sided tape or with the four self tapping screws supplied. Use the Switch as a template
and mark the mounting hole locations. Remove the Switch and drill the holes using a 3/16" drill bit
then install the screws.

WIRING

Red Connects to a switched 12 volt source.
Black Connects to ground.
White The rpm input wire. With an MSD Ignition, this connects to the Tach Output terminal.

On inductive ignitions, it connects to the coil negative terminal.

Yellow This is an activation wire and is Normally Open and will switch to ground. It connects

to the ground side of the device you plan to activate.

Gray This is an activation wire and is Normally Closed to ground. It will open the ground

path of a circuit.

Note: Inductive ignitions only.

M S D   •   W W W . M S D P E R F O R M A N C E . C O M   •   ( 9 1 5 )   8 5 7 - 5 2 0 0   •   F A X   ( 9 1 5 )   8 5 7 - 3 3 4 4

Figure 3 Wiring to an Inductive Ignition System.

INSTALLATION INSTRUCTIONS 3

Note: Capacitive discharge ignitions only.

Figure 4 Wiring to an MSD Ignition Control.

Figure 5 Wiring with an MSD Relay.

Figure 6 Wiring with an MSD Timing Control Retard.

M S D   •   W W W . M S D P E R F O R M A N C E . C O M   •   ( 9 1 5 )   8 5 7 - 5 2 0 0   •   F A X   ( 9 1 5 )   8 5 7 - 3 3 4 4

RPM Module Kits are supplied with five modules in a range of 200 rpm increments. There are even
number sets and odd number sets available. Example: PN 8746 includes 5,000, 5,200, 5,400, 5,600,
5,800 modules.

Kit Even Set Odd Set

3,000 Kit PN 8743 87431
4,000 Kit PN 8744 87441
5,000 Kit PN 8745 87451
6,000 Kit PN 8746 87461
7,000 Kit PN 8747 87471
8,000 Kit PN 8748 87481
9,000 Kit PN 8749 87491
10,000 Kit PN 8750 87501
11,000 Kit PN 8751 87511

Module Selectors: These Selectors
offer 12 different rpm limits at the
turn of a knob. Note: Even rpm in
200 rpm increments only.

RPM PART NUMBER

3,000 - 5,200 PN 8670
4,600 - 6,800 PN 8671
6,000 - 8,200 PN 8672

For rpm settings below 3000 rpm,
MSD offers an adjustable Module,

7,600 - 9,800 PN 8673
9,000 - 11,200 PN 8674

PN 8677

Service

In case of malfunction, this MSD component will be repaired free of charge according to the terms of the warranty.

When returning MSD components for warranty service, Proof of Purchase must be supplied for verification. After
the warranty period has expired, repair service is based on a minimum and maximum fee.

All returns must have a Return Material Authorization (RMA) number issued to them before

being returned. To obtain an RMA number please contact MSD Customer Service at 1 (888) MSD-7859 or visit
our website at www.msdperformance.com/rma to automatically obtain a number and shipping information.

When returning the unit for repair, leave all wires at the length in which you have them installed. Be sure to include
a detailed account of any problems experienced, and what components and accessories are installed on the vehicle.
The repaired unit will be returned as soon as possible using Ground shipping methods (ground shipping is covered
by warranty). For more information, call MSD at [phone]. MSD technicians are available from 7:00 a.m. to
5:00 p.m. Monday - Friday (mountain time).

Limited Warranty

M

SD warrants this product to be free from defects in material and workmanship under its intended normal use*,
when properly installed and purchased from an authorized MSD dealer, for a period of one year from the date of
the original purchase. This warranty is void for any products purchased through auction websites. If found to be
defective as mentioned above, it will be repaired or replaced at the option of MSD. Any item that is covered under
this warranty will be returned free of charge using Ground shipping methods.
This shall constitute the sole remedy of the purchaser and the sole liability of MSD. To the extent permitted by
law, the foregoing is exclusive and in lieu of all other warranties or representation whether expressed or implied,
including any implied warranty of merchantability or fitness. In no event shall MSD or its suppliers be liable for special
or consequential damages.
*Intended normal use means that this item is being used as was originally intended and for the original application
as sold by MSD. Any modifications to this item or if it is used on an application other than what MSD markets the
product, the warranty will be void. It is the sole responsibility of the customer to determine that this item will work for
the application they are intending. MSD will accept no liability for custom applications.

M S D   •   W W W . M S D P E R F O R M A N C E . C O M   •   ( 9 1 5 )   8 5 7 - 5 2 0 0   •   F A X   ( 9 1 5 )   8 5 7 - 3 3 4 4

© 2012 Autotr onic Contro ls Corporat ion

FRM28660 Revised 12/11 Printed in U.S.A.