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RAC Distance Measuring Instruments
These units are installed in a vehicle and used to do distance measuring, accurate to one foot per mile. The current instruments available are the
RAC Plus series. The RAC-100 & 200 series units were available from 1990 to 2005. They were replaced by the RAC Plus series in March 2005.
If you do not find an answer to your problem/question, fill out and submit a support request form.
RAC Distance Measuring Instruments
These units are installed in a vehicle and used to do distance measuring, accurate to one foot per mile. The current instruments available are the
RAC Plus series. The RAC-100 & 200 series units were available from 1990 to 2005. They were replaced by the RAC Plus series in March 2005.
If you do not find an answer to your problem/question, fill out and submit a support request form.
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Frequently Asked Questions
RAC Plus Series
My RAC Plus won't count. What's wrong?
In most cases, when a RAC Plus won't count, it is not the unit itself that has the problem.
It is usually a problem with the interface sensor or wiring. Full details...
My RAC Plus counts while the vehicle is not moving. What's wrong?
There are three possible causes for this.
1. Your wiring may be picking up stray pulses from the vehicle. This can occur if the wiring is to close to the alternator, spark plugs, distributor cap or engine coil.
2. Your ground wire may not be connected properly. Double check its connections.
3. Your Modular Distance Sensor may not be working correctly. Contact us for information on getting replacement parts.
My RAC Plus counts in increments of 2, 5, 10, etc. What's wrong?
Adjust the rotary switch on the modular distance sensor and then recalibrate. Refer to How do I adjust the Vehicle Speed Sensor pulse rate? for more information.
How do I calibrate my RAC Plus?
Follow the seven steps of the calibration procedure to properly calibrate your instrument. Full details...
My calibration number is outside the recommended range of .500 to 1.200. What should I do?
Adjust the rotary switch on the modular distance sensor and then recalibrate. Refer to How do I adjust the Vehicle Speed Sensor pulse rate? for more information.
How do I adjust the Vehicle Speed Sensor pulse rate?
There is a rotary switch located on the modular sensor that should be changed. Full details...
What is the difference between the RAC Plus I and the RAC Plus III?
The RAC Plus I is the base unit of the RAC Plus series. The RAC Plus II contains all of the features of the RAC Plus I with the addition of 3500-event memory storage. This
allows for saving of surveys for later download to a computer. The RS-232 port used for downloading can also be used to control the unit in a real-time mode from a lap-top
computer. The RAC Plus III contains all of the features of the RAC Plus II and adds the ability to view and record GPS coordinates while recording distance.
How do I check the firmware version of the RAC Plus?
To see what firmware version is in your RAC Plus, turn the unit on while holding down the CLR button. The top display will show the firmware version and the bottom display will
show the model version, with 100 for RAC Plus I, 200 for RAC Plus II and 300 for RAC Plus III.
Where is the correct location to connect the Modular Distance Sensor to the Vehicle's Speed Sensor?
Most vehicles should have a 2-wire output from the VSS.
On most Ford and Chrysler pick-up trucks, the best place is on the rear end differential housing using the rear ABS signal.
On General Motors pick-up trucks, the best place is the VSS at the transmission.
On many vehicles (both trucks and autos) you can go to the cruise control signal or to the vehicle ECU which is often located under the dashboard.
Note: Vehicle wiring changes from year to year and model to model. For vehicle-specific color code information, submit a Support Request Form. Your local Auto/Truck dealer
can also usually tell you where the VSS can be located on your vehicle
Connect the red wire of the long 20’ VSS cable to the high speed signal wire from the vehicle’s speed sensor. (The black wire is for optional use with vehicles made before
2002. In these vehicles, it should be connected to the low speed signal wire of the vehicle’s speed sensor or chassis ground.) 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.
I would like to read data from the RAC Plus III directly into my own program. Can I do that?
Yes, you can control the RAC Plus III, and read data from it, using your own custom software. We provide a RAC Plus III Real Time Interface document that can help you with this.
Do you still make a RAC Plus II?
No. All of the capabilities of the RAC Plus II are found in the RAC Plus III, which made the RAC Plus II redundant.
RAC 100 & 200 Series
My RAC-100/RAC-200 won't count. What's wrong?
In most cases, when a RAC-100 or 200 won't count, it is not the unit itself that has the problem.
It is usually a problem with the interface sensor or wiring. Full details...
My RAC-100/RAC-200 counts while the vehicle is not moving. What's wrong?
There are three possible causes for this.
1. Your wiring may be picking up stray pulses from the vehicle. This can occur if the wiring is to close to the alternator, spark plugs, distributor cap or engine coil.
2. Your ground wire may not be connected properly. Double check its connections.
3. Your Modular Distance Sensor may not be working correctly. Contact us for information on getting replacement parts.
My RAC-100/RAC-200 counts in increments of 2, 5, 10, etc. What's wrong?
Your calibration number may be too high. The calibration number should be between .500 and 1.200. You can lower the calibration number by adjusting the rotary switch on the
sensor. Refer to How do I adjust the Vehicle Speed Senor pulse rate? for more information.
How do I calibrate my RAC-100/RAC-200?
Follow the six steps of the calibration procedure to properly calibrate your instrument. Full details...
My calibration number is outside the recommended range of .500 to 1.200. What should I do?
Adjust the rotary switch on the modular distance sensor and then recalibrate. Refer to How do I adjust the Vehicle Speed Sensor pulse rate? for more information.
How do I adjust the Vehicle Speed Sensor pulse rate?
There is a rotary switch located on the modular sensor that should be changed. Full details...
What is the difference between the RAC-100 and the RAC-200?
The RAC-200 contains all of the features of the RAC-100 with the addition of 1000-event memory storage. This allows for saving of surveys for later download to a computer
using the WinRAC program. The RS-232 port used for downloading can also be used to control the unit in a real-time mode from a lap-top computer.
Where is the correct location to connect the Modular Distance Sensor to the Vehicle's Speed Sensor?
Most vehicles should have a 2-wire output from the VSS. On most Ford and Chrysler pick-up trucks, the best place is on the rear end differential housing using the rear ABS
signal. On 2005 and later Ford trucks, connect at the top rear of the transmission tail shaft (on 4x4 where the transmission meets the transfer case) with the JAMAR red wire to
the vehicle's blue/yellow wire. Leave the JAMAR black wire disconnected.
On General Motors pick-up trucks, the best place is the VSS at the transmission.
On many vehicles (both trucks and autos) you can go to the cruise control signal or to the vehicle ECU which is often located under the dashboard.
Note: Vehicle wiring changes from year to year and model to model. For vehicle-specific color code information, submit a Support Request Form. Your local Auto/Truck dealer
can also usually tell you where the VSS can be located on your vehicle
Connect the red and black wires of the long 20’ VSS cable to the wires from the vehicle’s speed sensor. 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.
RAC Plus Series
My RAC Plus won't count. What's wrong?
In most cases, when a RAC Plus won't count, it is not the unit itself that has the problem.
It is usually a problem with the interface sensor or wiring. Full details...
My RAC Plus counts while the vehicle is not moving. What's wrong?
There are three possible causes for this.
1. Your wiring may be picking up stray pulses from the vehicle. This can occur if the wiring is to close to the alternator, spark plugs, distributor cap or engine coil.
2. Your ground wire may not be connected properly. Double check its connections.
3. Your Modular Distance Sensor may not be working correctly. Contact us for information on getting replacement parts.
My RAC Plus counts in increments of 2, 5, 10, etc. What's wrong?
Adjust the rotary switch on the modular distance sensor and then recalibrate. Refer to How do I adjust the Vehicle Speed Sensor pulse rate? for more information.
How do I calibrate my RAC Plus?
Follow the seven steps of the calibration procedure to properly calibrate your instrument. Full details...
My calibration number is outside the recommended range of .500 to 1.200. What should I do?
Adjust the rotary switch on the modular distance sensor and then recalibrate. Refer to How do I adjust the Vehicle Speed Sensor pulse rate? for more information.
How do I adjust the Vehicle Speed Sensor pulse rate?
There is a rotary switch located on the modular sensor that should be changed. Full details...
What is the difference between the RAC Plus I and the RAC Plus III?
The RAC Plus I is the base unit of the RAC Plus series. The RAC Plus II contains all of the features of the RAC Plus I with the addition of 3500-event memory storage. This
allows for saving of surveys for later download to a computer. The RS-232 port used for downloading can also be used to control the unit in a real-time mode from a lap-top
computer. The RAC Plus III contains all of the features of the RAC Plus II and adds the ability to view and record GPS coordinates while recording distance.
How do I check the firmware version of the RAC Plus?
To see what firmware version is in your RAC Plus, turn the unit on while holding down the CLR button. The top display will show the firmware version and the bottom display will
show the model version, with 100 for RAC Plus I, 200 for RAC Plus II and 300 for RAC Plus III.
Where is the correct location to connect the Modular Distance Sensor to the Vehicle's Speed Sensor?
Most vehicles should have a 2-wire output from the VSS.
On most Ford and Chrysler pick-up trucks, the best place is on the rear end differential housing using the rear ABS signal.
On General Motors pick-up trucks, the best place is the VSS at the transmission.
On many vehicles (both trucks and autos) you can go to the cruise control signal or to the vehicle ECU which is often located under the dashboard.
Note: Vehicle wiring changes from year to year and model to model. For vehicle-specific color code information, submit a Support Request Form. Your local Auto/Truck dealer
can also usually tell you where the VSS can be located on your vehicle
Connect the red wire of the long 20’ VSS cable to the high speed signal wire from the vehicle’s speed sensor. (The black wire is for optional use with vehicles made before
2002. In these vehicles, it should be connected to the low speed signal wire of the vehicle’s speed sensor or chassis ground.) 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.
I would like to read data from the RAC Plus III directly into my own program. Can I do that?
Yes, you can control the RAC Plus III, and read data from it, using your own custom software. We provide a RAC Plus III Real Time Interface document that can help you with this.
Do you still make a RAC Plus II?
No. All of the capabilities of the RAC Plus II are found in the RAC Plus III, which made the RAC Plus II redundant.
RAC 100 & 200 Series
My RAC-100/RAC-200 won't count. What's wrong?
In most cases, when a RAC-100 or 200 won't count, it is not the unit itself that has the problem.
It is usually a problem with the interface sensor or wiring. Full details...
My RAC-100/RAC-200 counts while the vehicle is not moving. What's wrong?
There are three possible causes for this.
1. Your wiring may be picking up stray pulses from the vehicle. This can occur if the wiring is to close to the alternator, spark plugs, distributor cap or engine coil.
2. Your ground wire may not be connected properly. Double check its connections.
3. Your Modular Distance Sensor may not be working correctly. Contact us for information on getting replacement parts.
My RAC-100/RAC-200 counts in increments of 2, 5, 10, etc. What's wrong?
Your calibration number may be too high. The calibration number should be between .500 and 1.200. You can lower the calibration number by adjusting the rotary switch on the
sensor. Refer to How do I adjust the Vehicle Speed Senor pulse rate? for more information.
How do I calibrate my RAC-100/RAC-200?
Follow the six steps of the calibration procedure to properly calibrate your instrument. Full details...
My calibration number is outside the recommended range of .500 to 1.200. What should I do?
Adjust the rotary switch on the modular distance sensor and then recalibrate. Refer to How do I adjust the Vehicle Speed Sensor pulse rate? for more information.
How do I adjust the Vehicle Speed Sensor pulse rate?
There is a rotary switch located on the modular sensor that should be changed. Full details...
What is the difference between the RAC-100 and the RAC-200?
The RAC-200 contains all of the features of the RAC-100 with the addition of 1000-event memory storage. This allows for saving of surveys for later download to a computer
using the WinRAC program. The RS-232 port used for downloading can also be used to control the unit in a real-time mode from a lap-top computer.
Where is the correct location to connect the Modular Distance Sensor to the Vehicle's Speed Sensor?
Most vehicles should have a 2-wire output from the VSS. On most Ford and Chrysler pick-up trucks, the best place is on the rear end differential housing using the rear ABS
signal. On 2005 and later Ford trucks, connect at the top rear of the transmission tail shaft (on 4x4 where the transmission meets the transfer case) with the JAMAR red wire to
the vehicle's blue/yellow wire. Leave the JAMAR black wire disconnected.
On General Motors pick-up trucks, the best place is the VSS at the transmission.
On many vehicles (both trucks and autos) you can go to the cruise control signal or to the vehicle ECU which is often located under the dashboard.
Note: Vehicle wiring changes from year to year and model to model. For vehicle-specific color code information, submit a Support Request Form. Your local Auto/Truck dealer
can also usually tell you where the VSS can be located on your vehicle
Connect the red and black wires of the long 20’ VSS cable to the wires from the vehicle’s speed sensor. 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.
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