Modern car interiors have a striking resemblance with airplane cockpits, considering the various dials and gauges installed on the front dashboard. One of those dials belongs to the tachometer.
What is a Tachometer?
The engine is a car's heart and the RPM (Revolutions Per Minute) reading is like the pulse rate recording. Engine's RPM is indicator of power drawn from the engine. A tachometer is a device used to provide live measurement of an engine's RPM value. Like a high pulse is bad for the heart, a high RPM rate is not good for the car engine. High RPM values can lead to overheating of the engine and eventually failure.
For efficiency of the engine, it is important that the car driver changes gears according to the RPM values. That's why, tachometer is an important car part that needs to be in fully functional condition. It helps in monitoring the engine working condition, its overall health and to diagnose car engine problems, if there are any. Modern cars are fitted with digital tachometers, instead of the earlier analog dial tachometers.
Tachometers measure the RPM of an engine by measuring the crankshaft rotation rate. This is typically done by attaching an electrical generator device that generates electric current proportional to the rotation rate of the crankshaft. The instrument is calibrated to display RPM reading proportional to the generated current. It is essential that one has a working tachometer on the dashboard as without it, there is no way you can keep an eye on a working of an engine.
There are several types of problems that could occur with a tachometer. They can mostly be traced to be mechanical and electronic problems. Of the many car problems that can crop up, tachometer problems are some of the easiest to solve. Here I explain some simple troubleshooting techniques.
Tachometer Display Failure
If you notice that a tachometer is not showing any reading on its display, the reason might be the failure of the LED display. LED displays that have been in use for long, may blank out due to damage. Getting the LED display replaced will fix the problem quite easily. This is the simplest task when troubleshooting a tachometer.
Check Wire Connections
Sometimes, corroded wire connections and breakage may be the reason for the tachometer not working. A classic symptom of a loose wire connection is erratic display of readings. Check the tachometer wiring section in the car manual. If you don't find it there, get the appropriate Hayne's manual for your car.
With the tachometer wiring diagram in front of you, check the underlying connections. Trace the wire connection from the crankshaft attached generator to the display panel on your dashboard. Check the connection with the battery power source and the engine control unit. Make sure that the tachometer is grounded properly. Fix loose connections if any and replace corroded wires. Make sure that you put the connections back as they were.
Another major source of problems in a tachometer is calibration which has gone out of sync. You may notice that RPM readings are really low or unusually high compared to engine's working status. That is a clear indicator of problems with calibration. This problem can be taken care of, by resetting the digital tachometer. Just refer to the manufacturer's manual for details regarding resetting the device.
Check With a Replacement Tachometer
To check whether it's a wiring problem or an internal problem of tachometer, install a replacement tachometer for testing. If it does work, then the problem lies with the tachometer. Just get it checked from a technician in a car repair center.
If you find it difficult to diagnose the exact problem, then it is best to leave tachometer repair to professionals. In cases of total failure or breakdown, there will be no alternative to complete replacement.