MSD 8956 User manual

IMPORTANT: Read the instructions before attempting the installation.
Parts Included
1 - RPM Window Switch
4 - Self Tapping Screws
Note: RPM Modules must be purchased separately. See the chart on the last page for part
numbers.
The RPM Activated Window 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 Window Switch has a circuit that activates a device by providing a ground path at a desired
rpm (Figure 1). The ground will be removed at a different rpm to deactivate the device. If no rpm
module is installed, the device will remain activated as long as the rpm is above the activation amount.
Figure 1 Operation of the RPM Window Switch.
4 - Heat-Shrink Caps
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MSD RPM Activated Window Switch
PN 8956
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2 INSTALLATION INSTRUCTIONS
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CYLINDER PROGRAMMING
The Window 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
head-shrink caps. Use a heat gun or other heat source to shrink the cap for a good seal.
Figure 3 Wiring to an Inductive Ignition System.
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 the circuit ground wire (normally open switch to ground). It connects to the
ground side of the device you plan to activate.
Note: Inductive ignitions only.
Figure 2 Cylinder Select Loops.
CYLINDERS CUT LOOPS
8 NONE
6 RED
4 RED & BLUE

INSTALLATION INSTRUCTIONS 3
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Figure 4 Wiring to an MSD Ignition Control.
Figure 5 Wiring with an MSD Relay.
Note: Capacitive discharge ignitions only.

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
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.
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).
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© 2014 MSD LLC
FRM24819 Revised 01/14 Printed in U.S.A.
Module Selectors: These Selectors offer
12 different rpm limits at the turn of a knob.
Note: Even rpm in 200 rpm increments only.
For rpm settings below 3000 rpm, MSD offers
an adjustable Module, PN 8677.
RPM PART NUMBER
3,000 - 5,200 PN 8670
4,600 - 6,800 PN 8671
6,000 - 8,200 PN 8672
7,600 - 9,800 PN 8673
9,000 - 11,200 PN 8674