Jamar RAC Plus I, User Manual, Page: 19 / 56

2-9
Chapter 2 — Installation
The number of pulses per mile from a vehicle will vary with the make and model.
Your calibration factor should be between .500 and 1.200.
If not, adjust the
rotary switch then recalibrate to reach a calibration number within this range.
If the speedometer does not respond to
vehicle movement, simply switch the
RED wire to the other VSS wire.
Most vehicles should have a 2-wire output from the VSS.
Dodge & Ford trucks may have the VSS located on top of the rear end housing instead of at
the transmission. It will normally be a 2-wire output, small gauge wire.
Connect the red wire of the long 20’ VSS cable to the high-speed signal wire of the vehicle’s
speed sensor. (The black wire is for optional use with vehicles made before 2002.) Crimp-on tap
splice connectors are supplied for convenience on initial installation. However, we recommend
removing the tap splice connectors and reconnecting using wire to wire solder once you are
sure all connections to the VSS are proper. Insulate with sealant/electrical tape as needed.
Fig. 2.9 –MDS Installation Diagram
Vehicle Speed
Sensor (VSS)
Fire
Wall
Fire
Wall
Tap Splice
Connector
Battery
RA
C Connector
Gr
ound Blac
k
+12
VDC Red
High Speed Signal
Low Speed Signal
+ –
The black wire is is for
optional use with vehicles
made before 2002.
Red Blac
k
Filter Toggle
As a default, the Filter toggle should be set to ‘Filter
Off’. However, on some vehicles there is ‘noise’ on
the speed sensor line that causes the RAC to count
up while the vehicle is not moving. The filter toggle
should be flipped to ‘Filter On’ in these cases.
Fig. 2.8 –
Filter Toggle
Filter toggle should always be
OFF
unless
you are getting ‘noise’ on the speed sensor
line, which causes the RAC to count while
the vehicle is not moving.