In our day to day lives, to ensure proper road safety we should always drive within the speed limits. But how will you know at which speed you are driving if you have a faulty speedometer or speed sensor? Speedometers and speed sensors both play a crucial role by indicating the exact speed of the vehicle to keep you safe and also makes sure you avoid those speeding tickets. Well, it is not rocket science to understand the basic principle of a speedometer.
Speed Sensor Mechanism:
Fig: Speed Sensor ( TRENDY truck parts)
Speed sensor works on a very simple principle: there is a special socket that goes to either the output shaft of the transmission or the crankshaft of the engine. When the shaft rotates, the special socket attached to it also rotates. It is a sender device used for reading the speed of a vehicle’s wheel rotation. It usually consists of a toothed ring and pickup.
Fig: Speed Sensor (TRENDY truck parts)
A magnet is linked to the speedometer over which the speed cup is present. An indicator rod is connected with the speed cup which is further connected to a hair spring. The indicator housing is attached to the indicator rod which shows the speed outside in the speedometer.
Fig: TATA 407 speedometer
When the output shaft rotates, the speedometer cable connected to it also rotates. This cable in turn will make the magnet rotate This magnet will form a magnetic field and attract the metallic part of the speed cup. Due to this, the speed cup will be deflected and the indicator rod will rotate and deflect the hair spring. This indicator rod will move the needle in the indicator housing to show you the speed with which the vehicle is moving.
Some common problems with Speedometers:
A faulty Speed sensor can be detected using a computer/ mobile device by connecting the computer/ mobile device to the vehicle using bluetooth. A faulty vehicle speedometer sensor can cause a mix of problems. In fact, symptoms of a faulty speed sensor may also result in symptoms of other common components such as a defective coil pack or bad throttle position sensor. However, here is a list of the most common symptoms associated with a bad engine speed sensor:
- Transmission revs higher before it changes gears
- The truck’s transmission engages into overdrive later than required and sometimes will never go into the top gear
- Brakes are harder than normal
- Speedometer behaves inconsistently or does not work at all
- The check engine light comes on intermittently and intermittently when accelerating
- The overdrive on/off light blinks on and on for no reason
If your vehicle is experiencing any of the above problems, you should take your truck or vehicle into a local mechanic or garage or dealership to have them check through a computer diagnostic test on your vehicle.
How to check for accuracy?
Get a stopwatch. As you pass a kilometer marker on the road, turn on the stopwatch and drive till the next marker. As you reach the next marker, stop the Stopwatch. The second hand reading should be equal to the speed shown in the speedometer. Also, you can visit a mechanic to check for inaccuracy of the speedometer of your truck.
TRENDY has following speed sensor and flywheel sensor