FAQ | Roadwatch


What is RoadWatch and how does it work?

RoadWatch is a device that is able to measure the temperature of a surface by measuring the heat that is radiated by any object warmer than −459.67°Fahrenheit (referred to as absolute zero). This means everything that we encounter in the real world is radiating heat. The easiest way of thinking about this is to look at a standard incandescent light bulb that is turned on. We can see the light from the light bulb as well as feel the heat being radiated from it when we hold our hand near the bulb. The heat that we feel is known as infrared (IR) energy and is being radiated by anything warmer than absolute zero. The RoadWatch sensor is like your hand when held up to the light bulb. It can detect and measure the amount of IR energy being radiated by the light bulb. The light bulb is a lot hotter than a road surface when the air temperature is near freezing, but the road is still radiating IR energy. The RoadWatch sensor is a very sensitive IR measurement device and is able to measure the IR energy being radiated by the road and convert that measurement into the temperature of the road surface.

The RoadWatch sensor is based on infrared thermometer technology and for those who want a more technical description can click on this link.

What are the RoadWatch specifications?


  • System Operating Range: -40 to +150 °F
  • Thermal Shock: ISO 16750-4 (2010) Section
  • Water Immersion: ISO 20653 Section 6 IPX7
  • Salt Fog: ISO 16750-4 (2010) Section
  • Storage Range: -40 to 75 °C or -40 to 167 °F
  • Relative Humidity: 98% non-condensing
  • Vibration: 4g, sensor & display
  • Shock: 100g sensor element


  • Road Accuracy: ± 2 °F (15 to 100 °F under ambient stable)
  • Air Accuracy: ±2 °F (-40 to 131 °F) while moving > 5 MPH
  • Field Calibration: accuracy ±1 °F (0 to 100 °F)
  • Repeatability: ±1 °F under stable ambient conditions
  • Emissivity: factory calibrated at 0.96
  • Field of View Angle: 5° typical
  • Weight: 11oz sensor, 3oz display


  • Operating Voltage: 9-28Vdc
  • Current Requirement: 0.1A
  • Sensor Data Rate: 4 readings per second
  • J1708 Data Format
  • Bluetooth Low Energy v4.0 (849-1099-010)

How accurate is RoadWatch?


RoadWatch was initially designed to measure the road surface temperature most accurately (± 2°F / ± 1°C) when the ambient air temperature is between 23°F and 41°F (-5°C to +5°C). Unlike other manufacturers, the RoadWatch Bullet is fully calibrated from 15°F to 105°F for twelve air and road temperatures with ISO-9000 process controls and using a NIST traceable reference. Every sensor must pass a post-calibration verification to complete the manufacturing process.

Production/Calibration Realtime Screen

I want a RoadWatch, where can I buy one?

Where To Buy

Contact CVG customer service at 800-222-7328 to find nearest dealer or to order direct. You can also find your closest dealer here

I have an old RoadWatch. Where can I get replacement parts?

RW SS system replacement parts (Since June 2006)

Sensors can be replaced with the 849-0100-002 (Fahrenheit) or 849-0100-003 (Celsius) kits. The display can be replaced by the 849-0260-000 display only kit. The older rectangular EDAC connector based RW SS components will also require the 434-0104-000 adapter cable to replace the failed sensor or the 434-0105-000 to replace the failed display gage. These parts have limited supplies and can no longer be supported once current stock is gone.

Original RoadWatch RW-1 system replacement Parts (before June 2006)

The RW-1 was in production from 1995 to June 2006. Any RoadWatch sold before June 2006 will likely be a RW-1 system. The RW-1 system was discontinued because parts that were used in its design were no longer being manufactured. Because of this, there are no longer any RW-1 components available for replacement purposes. The only solution for failed RW-1 components is to replace the failed component with a new RW SS system.

RoadWatch 3 system replacement parts (2002 to 2009)

There were a small number of RW 3 systems sold from approximately 2002 until 2009 when the RW 3 was officially discontinued. The RW 3 was similar in appearance to the RW SS with the rectangular EDAC connector. The main difference is that the display gage only had a single temperature readout that “Flipped” between ambient air temperature for road temperatures higher than 37°F or less than 23°F. In other words, it only displayed the road surface temperature between 23°F and 37°F. The LED caution light on the display gage came on when it was showing the road surface temperature. The RW 3 sensor was only calibrated to read correctly in the displayed road surface temperature range of 23°F to 37°F. It was inaccurate outside of this range. Failed RW 3 sensors can be replaced by current RW SS sensors. The single temperature display gage used on the RW 3 is no longer available and if the RW 3 display fails, the customer needs to replace the RoadWatch system that they have with a new RW SS system. The RW 3 was based on the rectangular EDAC connector and will require the use of the 434-0104-000 adapter cable to replace the sensor.

Where is the best place to mount RoadWatch? Where not?

RoadWatch was originally designed to be installed on the frame rail of a “West Coast” style mirror. These mirrors have a ¾” tubular frame that allows the RoadWatch sensor to be attached using the standard clamp. This mounts the sensor at mirror height (approximately 6 feet) above the road surface. As long as the sensor is mounted in such a way that it cannot “see” the side of the vehicle, this is the best place to mount the mirror. The sensor has a 15 degree field of view. At a height of 6 feet (1.8 meters), the sensor sees a circular area on the road surface of approximately 19.3 inches (49 cm). An easy way to determine the road area target circle size is to divide the height of the sensor in inches (or cm) by 3.73. Mirror height mounting is the ideal location since it protects the sensor from road spray and slush as well as gives a large enough target area to obtain a good average of the road surface temperature.

Even though 6 feet above the road surface is ideal, the sensor will work correctly from about 6 inches (15 cm) above the road surface up to where the target spot size starts to see items other than the road (vehicle side, vehicles in adjacent lanes, side of the road, etc). If seeing the side of the vehicle is a problem, the sensor can be mounted at an angle away from the side of the vehicle. The sensor can be mounted up to an angle of 45 degrees in this type of situation.

 On smaller vehicles, the most successful mounting locations are high on the side of the cab using a small grab handle (GB-12) or the optional flat back mounting clamp (SK-1501). Some RoadWatch dealers sell other mounting accessories (e.g. MS Foster http://msfoster.com)

Locations not recommended to mount the RoadWatch sensor include any area that allows road spray or slush to contact the sensor lens face. This mainly happens when trying to mount the sensor in a low place such as the front bumper of the vehicle. Other areas that should not be used are any area that allows the sensor to see reflections from the engine or exhaust system off of the road surface (the road surface acts like a mirror to Infrared energy). Reflected heat will adversely affect the road surface temperature reading. Some of examples of areas that can cause problems of this nature are between the rails of a truck frame, between the cab and bed of pick-up trucks, near exhaust stacks on trucks, etc.

My RoadWatch is not reading correctly. How do I fix it?

Any inaccuracy in road or air temperatures result from failed RW SS components or the end user not understanding the conditions that are present when they think that the reading is inaccurate.

We rarely get questions about the air temperature measurement accuracy so any significant reported error is likely due to a failed sensor that will need to be replaced. The only real question to ask about inaccurate air temperature readings is if the RW SS sensor is in direct sunlight in a non-moving vehicle. Sitting in the Sun, like most everything else, will heat up the RW SS sensor above what the actual air temperature is at that time. A moving vehicle allows the Sun induced heating to be dissipated and the air temperature probe will measure the air temperature correctly.

Reports of inaccurate road temperature readings can be caused by many factors. Here are a few to verify.

  • Is the RW mounted too close to the side of the vehicle? Use warm object, like a cup of coffee while watching the display. If the cup is near the side of the vehicle and the display changes, the sensor needs to be moved to see only the road.
  • Was environment temperature suddenly changed when the error was noticed? Large sudden air temperature changes, like that of moving out from a heated garage to freezing outdoor temperature will temporarily cause inaccurate readings.
  • If ice water was used it works best to have a fine mix of slushy snow at the top. The water must not have any salt in it.
  • Use a RoadWatch Field Calibration System (FCS) as part of a QA calibration process to verify proper function and indication. Best practice recommendation call for annual checks as part of a pre-season readiness plan.

How do I get my RoadWatch calibrated?  I need an annual calibration service.

The RoadWatch SS sensor is factory calibrated and typically does not require calibration in the field. For sensors manufactured prior to January, 2010, there is no field adjustment that can be made to the sensor. For these sensors, if the RW SS is reading incorrectly, the sensor needs to be replaced. See the answer to the question “My RoadWatch is not reading correctly. How do I fix it?” for additional information.

We are currently developing a RoadWatch Field Calibration System (FCS) which will allow in-the-field accuracy verification and recalibrations on late model sensors.

I need a longer cable. What do I do?

CVG has three extension cables (4 foot, 12 foot, 16 foot) available that can be used to extend the length of the cable between the sensor and display gage (or other equipment). There are two groups of extension cables available. One for the old rectangular EDAC connector based RoadWatch based systems and one for the new M8 connector based RoadWatch systems. The old rectangular connector (EDAC) based cables are in limited supply and when current inventories of the cables are depleted, they will no longer be available.

M8 Connector Extension Cables:
1.5foot          434-1100-015
4 foot           434-1100-002
12 foot         434-1100-000
16 foot         434-1100-001

The extension cables can be connected together to allow total cable lengths of 100 feet between the sensor and display gage (or other equipment).

I can’t connect the RoadWatch parts together. The connectors don’t match.

The vendor of the rectangular (EDAC) connector based RW SS systems discontinued the manufacturer of that connector series. This required that we find a new connector to replace it. This was done and the first RoadWatch kits with the new connector (M8) were manufactured starting in November of 2008. The use of the rectangular connector was discontinued at that time are no longer available. As part of the transition plan, a last time buy of the rectangular connectors was made that allowed a short adapter cable to be manufactured on a limited basis until the supply of rectangular connectors is used up.

Please note that the adapter cables are no longer available as of June 2010. The only reliable recommendation is to replace both the RoadWatch sensor & display with a new RW SS kit. Customers that choose to attempt a cable splice must do so at their own risk. Incorrect wiring can cause new devices to fail and will not be covered by warranty.

What do the error messages mean?

The RW SS system does not display any error message. What the customer is usually seeing is the default mode that the display gage goes into when it is not able to communicate with the RW SS sensor. In this situation, the display will show dashes where the air temperature is normally displayed and a number (200 or 300) where the road temperature is normally displayed. The display will also blink about every 4 seconds as it does an internal reset.

The solution to this is to troubleshoot why the sensor and display are not communicating with each other.

  • Ask them to check that all connectors are fully seated and no damage to the interconnecting cable between the sensor and display as the first step.
  • The next thing to check is that the voltage supply to the display is at least 9 volts. If all of these check out, the likely failure is the sensor. If the sensor is still under warranty (installed less than a year), give them instructions on how to return it under warranty. If the sensor is out of warranty, give them the sensor replacement part number: 849-1100-002 for a Fahrenheit sensor, 849-1100-003 for a Celsius sensor.
  • If the failed sensor uses the rectangular connector (EDAC connector), they will need a new kit 849-1262-00x.

I need a manual. 

PDF versions of the manuals are available and can be emailed to customers who need new copies. The following manuals are available by part number:

  • Full RoadWatch kit owners manual: S001.111811
  • Integrated Mirror Owners Manual: 003-0046-000 Rev C
  • RS-232 Adapter Owners Manual: 003-0062-000 Rev C
Other useful Documents
  • Sensor Replacement Instructions: 003-0063-000 Rev C
  • RW SS Sensor J1708 bus Message Definitions: (no part number)
Note: These documents were current at the time that this was written. They may have been updated since then.

What is the warranty? 

The standard RoadWatch warranty is one (1) year from the date of installation of RoadWatch on the vehicle.

Since RoadWatch is sold through a dealer network and may sit on a shelf for several months, we usually allow up to six months of shelf sitting time before saying that the RoadWatch unit is out of warranty. Many end users cannot document installation dates. In this case, we usually allow a period of 18 months from the date of manufacturer as the warranty period. The date of manufacturer can be found on the part number labels that are on the various components of RoadWatch. We can also read an internally stored week code of manufacturer in the sensor if the date is not legible on the labels or if we suspect that the sensor is way out of the warranty period (end users have been known to deface the date on the label to try and get a warranty replacement).

What do I need to connect to “Brand X” dispenser/controller?

Many of the salt/sanding truck dispenser controller manufacturers have designed their equipment to interface to the RoadWatch system. We know about the major manufacturers (Dicky-John, Force America, Cirus Controls, etc) but there are several smaller controller manufactures that have designed interfaces to RoadWatch without our involvement. In either case, we direct the caller to contact the manufacturer of the controller equipment to see what they require to connect RoadWatch to their equipment.

One issue that may come up is that many of the controller manufacturers designed their equipment to use the original RoadWatch RW-1 system. This situation is addressed by the use of the RW SS RS-232 Adapter product (849-0099-000) that makes a RW SS system look like a RW-1 system to the controller equipment.

What can I do to connect RoadWatch to my AVL/GPS/other equipment?

AVL = Automatic Vehicle Location
GPS = Global Positioning Satellite

This has to be handled on a case-by-case basis. The manufacturer (not CVG) of the AVL/GPS/other equipment must provide an interface to the RoadWatch system as well as being able to decode the digital messages from the RoadWatch sensor to get the air and road surface temperatures.

If the caller is an end user customer, tell them to contact the maker of the equipment to see if they already have an interface to RoadWatch. Calls from the maker of AVL/GPS equipment needs to be directed to RoadWatch engineering to help the equipment maker design the necessary interface to RoadWatch.

Why do I need RoadWatch? I already have an indicator light on my mirror that comes on when it is icy.

Once a user has access to a RoadWatch, they quickly realize that the air temperature and road surface temperature can vary by several degrees. It is not unusual to see over 20°F difference. The “ice” indicator in many vehicles is designed to come on when the air temperature falls below some predefined air temperature (usually about 35°F). It is not measuring ice on the road.

See the answer to the “Why is the road temperature different than air temperature” question for more details.

Why is the road temperature different than air temperature?

There are several factors that enter into the reason why road surface temperature and air temperature will differ most of the time. Some of the easier to understand factors are the amount of direct sunshine that may be present, clear night time conditions allowing substantial radiation cooling, changing weather conditions (sudden warm or cold wind arriving), etc.

One of the hardest factors to understand is that radiation cooling at night can allow the road surface to be several degrees cooler than the air temperature. This can easily set up the conditions for “Black Ice” which can be very dangerous. This is where the RoadWatch can give the driver the information that they need to drive safely.

Does RoadWatch detect ice? 

RoadWatch does not detect ice. What it does is measure the road surface temperature only. If the road temperature is near or below freezing and weather conditions are such that moisture is available to freeze, then there may be ice on the road surface. Our standard statement is that we only provide road surface temperatures to the driver. It is still the driver’s responsibility to use the surface temperature as one piece of information to determine the road surface condition and to drive accordingly.

How fast is RoadWatch?

The RoadWatch sensor sends a road surface temperature measurement about 4 times a second. For a vehicle moving at 55 miles per hour, a reading every 0.25 seconds will be making a reading every 20 feet of road travel.

An example of where the road surface temperature may change rapidly is when travelling from ground road surface to a bridge deck surface. Bridge surfaces are typically colder than the ground road surface in cold weather conditions. The quick response feature of the RoadWatch sensor will immediately alert the vehicle driver when the vehicle enters onto the bridge surface.

The ambient air temperature is updated approximately every second.

What are the cable connector pin/signal definitions? 

The signal pin assignments for the M8 connector are:

Pin 1         
Pin 2          +12 VDC Power
Pin 3          J1708 H data
Pin 4          J1708 L data
Pin 5          Ground
Pin 6          Not Connected

Sensor cable connector
Note that the wire colors shown are not consistent in every cable – do not indicate signal name by wire color.

If not familiar with SAE J1708 data bus specifications, they need to contact SAE (Society of Automotive Engineers) to obtain documentation. RoadWatch engineering will work with customers to be able to interface to the J1708 data bus.

Where can I buy the new M8 connectors/cables?

Various length extension cables are currently available from CVG (434-1100-0xx).

Why does my RoadWatch show incorrect (funny numbers, wacky numbers, etc) readings when I key up my radio to transmit? 

The design of the RoadWatch Bullet has now passed the following EMC emissions and immunity specifications:

  • CISPR25 2002 Sections 6.2,6.3 and 6.4: class 4
  • ISO 11452-4:2005

Effects from radio transmitters should no longer impact the indications

Although the RoadWatch system was designed to comply with the SAE radio interference specifications, the very small infrared signals that the RoadWatch sensor is required to measures can only be done with very high gain amplifiers in the sensor. Any high gain amplifier will also be able to amplify very small radio signals that are near the sensor. Since the sensor must be able to “see” the road surface in order to measure the temperature, the sensor cannot be completely enclosed in a metal shield. The sensor requires a window in the metal shield to see the road surface.

When a nearby radio is keyed up to transmit, the radio signal from the radio can interfere with the operation of the RoadWatch sensor. This will result in incorrect readings from the RoadWatch sensor. The incorrect readings will return to normal as soon as the radio is no longer transmitting. This does not harm or damage the sensor.

The only thing that can be done is to move the RoadWatch sensor as far away from the radio antenna as possible. If a radio antenna is mounted on the same mirror bracket as the RoadWatch sensor, one solution is to move the RoadWatch sensor to the other side outside mirror or to some other location.