What is an Indicator Lamp?

Lori Kilchermann

An indicator lamp is a warning device used to alert drivers of potential problems with their vehicles. Functions such as oil pressure, water temperature and the voltage are all typically wired into dashboard indicator lamps. When there is a potential problem or a dangerous reading from a engine sensor, the indicator lamp will illuminate. Many vehicles have both full-functioning gauges that show the reading of the function as well as an indicator lamp. Typically, lower-optioned and base-packaged vehicles will possess only the indicator lamp system.

An indicator lamp serves notice that the vehicle should be checked and diagnosed by a mechanic.
An indicator lamp serves notice that the vehicle should be checked and diagnosed by a mechanic.

For every function of the automobile engine, a sensor exists to transmit readings back to the dashboard. This system of warning lights and function indicators allows the driver to have an understanding of how the engine is operating. The sensors are programed to send a signal to the indicator lamp in the case of a non-standard sensor reading. When this signal is sent, the warning light illuminates, telling the driver there is a problem. The situation can then be assessed, and the driver can determine if immediate service is warranted or if the vehicle can continue on and be serviced later.

Although rare, an occasional faulty sensor can trigger a reaction from a warning lamp. When this happens, it can typically only be detected through testing of the sensor itself. While a mechanical gauge is triggered by the actual component being measured, such as water temperature or oil pressure, the indicator lamp uses electrical senders that measure the function against a go, no-go parameter engineered into the sensor. This type of system is not as accurate as the mechanical gauge, though it is more easily understood by the average driver.

Many automobile operators have no idea what their proper engine oil pressure or temperature should be before it is considered overheating. Most drivers, on the other hand, do understand that a problem exists when a warning light is illuminated on the vehicle's dashboard. The indicator lamp typically has the engine's function displayed inside the illuminated light—when the lamp marked "Temp." is illuminated, the driver understands that the vehicle's temperature is presenting a problem. When developing the warning system, it was understood that a driver must posses some mechanical ability or knowledge to decipher the readings of the mechanical gauges. Designers reasoned, however, that everyone could understand that there was a problem with the vehicle if a bright red light suddenly came on within the dashboard.

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