Speedometer Not Working Properly
Be it any vehicle, the speedometer is what gives the driver or rider information on the speed. This helps the
driver realize how fast or slow he is moving. Traditional speedometers were manual and used wires to
determine speed while most modern vehicles these days use speed sensors for the same. Common
speedometer problems include a faulty sensor, problem with the wiring or the speedometer dial
malfunctioning. Troubleshooting speedometer not working properly problems in , mostly call for a
replacement of the speed sensor or cable, depending upon the vehicle. Both these repair jobs are simple to
perform and can easily be done at home.
How Does a Speedometer Work?
Before moving on to troubleshooting speedometer not working problems, it is important to understand
exactly how does the speedometer work. In the 19th century, almost all vehicles used the Eddy Current
speedometers. In these speedometers, a cable is connected from the front wheel to the speedometer, where it
is joined to a magnet. Surrounding this magnet is the speedometer cup, which is joined to a spring and at the
wheel. As the vehicle moves ahead, rotation of wheels causes the cable and magnet to spin. This results in a
revolving electric current getting formed in the speedometer cup, and it also creates a magnetic field in
there. This magnetic field gets pulled by the magnet in the speedometer. The magnetic pull is directly
proportional to the speed at which the wheels rotate. So whenever you ride fast, the magnetic pull moves the
indicator on your dial higher, and as you slow down the spring starts holding back the indicator, even more
until it reaches zero.
The traditional eddy current speedometers have now been replaced in most vehicles by digital speedometers.
In these type of speedometers, there is a sensor on the car's rotating shaft. Also, the rotating shaft has a
magnet joined to it and is placed besides a magnetic sensor. A tiny electric current, in form of a pulse, is
produced whenever the rotating shaft passes the sensor. This pulse rate is calculated by a little computer and
sent to the dial where you can see the car's speed.
Speedometer Not Working Properly Problems
Speedometer problems arise when there is trouble anywhere in the above mentioned functioning process.
The most common ones are problems in the speed signal sensor, as a result of which the speedometer stops
working. If you notice problems in gear transmission or find the 'check engine' light on, it is because of a
faulty speed signal sensor. In case of your speedometer using the 'eddy current' technology, there could be a
trouble with the connecting cable which causes this problem. Ticking noises are a sign of this problem. In
either case, you will need to replace the speedometer cable or the speed sensors to solve your speedometer
not working problem.
Troubleshooting Speedometer Not Working Properly Problems
Speedometer Cable Replacement
Take out the engine cover and doghouse to remove the speedometer cable from your car. Take out the bolt
from under the dashboard, so that you can easily access the old speedometer cable. Also remove the nut on
the rotating shaft and pull the speedometer cable out through the passage. Remove the clamps present on the
transmission and engine compartment.
Once you have removed the old speedometer cable from your car, you need to replace it with a new one. In
the adapter, fix the square end of the new cable and also tighten the nut on the rotating shaft. Pass the new
cable through the passage and tighten the bolt at its rear end. This end should be fixed at the speedometer's
square hold. Fix back the clamps you earlier removed and also put back the engine cover.
Speed Sensor Replacement for Front Wheel Drive Vehicles
You will find the speed sensor behind the engine above the trans-axle. Take out the connecting hose, air
cleaner and electrical connector from above the sensor. With help of a 10 mm socket, take out bolts keeping
the sensor in place. Simply twist the sensor to take it out. Fix the new sensor in place and tighten bolts
around it. Attach back the hose, air cleaner and the electrical connector on to the sensor.
Speed Sensor Replacement for Rear Wheel Drive Vehicles
You will find the speed sensor on the driver's side behind the transmission. Raise the vehicle up from the
driver's side and put a jack stand below to hold it there. Disconnect electrical connectors present on the
sensor and take out bolts keeping the sensor in place, using a socket. Take out the sensor carefully and fix a
new one in its place. Attach the electrical connector to it and tighten it.
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Not every speedometer not working problem needs a replacement job. It depends on the cause. In case the
dial is the problem, you can easily replace it alone. Problems with the little computer reading sensor signals
call for the computer to be replaced. It is therefore important for you to take your car to a car mechanic and
diagnose the predicament, before jumping onto any conclusions and trying to solve it yourself.
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