When you look at a modern car dashboard, you see a lot of gauges and symbols, which can seem like a foreign language to you.
When it comes to car dashboard gauges, it can be challenging to figure out what is important as there are so many types of gauges. Every gauge on the car dashboard serves a purpose, which is why it is valuable for you to understand what you are looking at.
In this guide, I will discuss all of the important features of a car dashboard. I will also look at the relevant warning lights that accompany each of the gauges.
7 Types of Gauges in a Car
If you own or have driven a vehicle, you must have seen gauges (and maybe even wondered what some of them mean). Most common are the speedometer and the tachometer.
Often you’ll also see a fuel gauge, temperature gauge, and oil pressure gauge. An instrument cluster will sometimes also contain a voltmeter to show battery charge and an odometer to show the mileage of the car.
Here is a more thorough list of the seven common gauges that you will see in almost every vehicle:
#1. Speedometer.
In earlier vehicles, the speedometer was the most regularly used gauge. Speedometers were normally driven by a cable that would spin, which is contained inside a flexible tube. The cable is connected on one end to the speedometer and on the other end to the speedometer gear in the transmission.
Most vehicles today have replaced the speedometer cable with an electronic sensor to measure wheel speed and send a signal to an electronically driven speedometer.
The speedometer can be inaccurate when tires are larger in diameter than original equipment tires, causing the speedometer to read you are going slower than you actually are.
When early vehicles were using a speedometer cable, it is possible to have an incorrect speedometer gear in the transmission, causing an inaccurate reading. This can be done sometimes when a replacement transmission is taken from a junkyard and installed in another vehicle. Most of the good transmission shops will know to make sure there is a correct speedometer gear in the new transmission.
Newer vehicles with electronic speedometers allow the computer to have settings for speedometer calibration when needed, allowing a technician to calibrate for different sized tires. The speedometer calibrations typically require special equipment to do this type of adjustment, such as diagnostic scanners.
#2. Tachometer.
The tachometer indicates how fast the engine is turning, in RPM (Revolutions Per Minute). This is useful with a standard shift transmission as you will want to shift at the best RPM for fuel economy or best acceleration.
The tachometer is likely the least used gauge in a car with an automatic transmission. You should never run the engine so fast that the tach goes into the red zone since this could damage the engine.
Some engines are protected by the engine computer from going into the red zone. Either way the tachometer shows numbering in single digits, for instance 1, 2, 3, etc. Somewhere, you may see an indicator that says “RPM x 1000.”
This means you multiply the reading by 1000 to get the real RPM, so if the needle is pointing to 2, the engine is running at 2000 RPM.
#3. Fuel Gauge.
The gauge is designed to be inaccurate! After filling, the tank will stay on full for a long time, then slowly drop until 3/4, and then drop faster until the last quarter goes very fast.
This is kind of psychological misdirection to create the idea that the car gets better gas mileage enough to lessen complaints from new car buyers during that time window after they buy the car.
This fuel gauge is probably more accurate than most. Notice the difference between 3/4 to full and empty to 1/4.
When the needle goes below E, generally there is still 1 or 2 gallons left in reserve. To find out for sure, you have to take out your owner’s manual and find out how many gallons the tank holds, then next time you fill an empty tank, check how many gallons it took to fill it. The difference is your reserve.
Note: It is generally a good idea to not let your tank drop below 1/4. This is because part of the fuel pump is submerged in fuel at the bottom of the tank. Liquid fuel plays a role in keeping fuel pumps cooler.
If the level goes too low and uncovers the pump, the pump will run hotter than normal. If you do this often enough, you could shorten the life of the fuel pump and ultimately cause it to fail.
#4. Temperature Gauge/Warning Light.
This gauge shows engine coolant temperature, in degrees. When you first turn on the car, it will be cold. If you turn the heater on when the engine is cold, it will blow cold air. Once the gauge starts moving away from cold, you can turn the heater and get warm air.
Most temperature gauges, do not have degrees like this gauge, it reads cold, hot, and a normal range as depicted in the dash panel at the top of this page.
It is very important to monitor the temperature gauge to be sure that the engine is not overheating. If a you notice the gauge is reading much hotter than it normally does and the temperature outside is not a lot hotter than normal, have the cooling system checked right away.
Note: If the temperature gauge moves to hot, or if the temperature warning lite comes on, the engine is overheating! Safely pull off of the road, turn the engine off, and let the engine cool. An overheating engine can quickly cause severe engine damage!
#5. Oil Pressure Gauge/Warning Light.
The oil pressure gauge checks that the pressure by pounds per square inch. Oil pressure is like the blood pressure for the engine. The oil cannot allow the engine to fail if it doesn’t have the correct oil pressure.
If the oil pressure gets low enough, a light should come on. Stop immediately and have it checked. The gauge could just mean that the system needs oil, which is just to fill up the oil.
#6. Voltmeter/Warning Light.
The voltmeter tells you the condition of the charging system. In order to get the engine to start, the battery should be fully charged.
When the voltmeter shows an out of normal reading, either high or low, it will need to be checked. With this warning light, you have just a little forewarning that something is wrong, you may not have to stop immediately.
#7. Odometer.
The odometer is a gauge that counts miles. It will show how many miles are on the car for its life and for the trip that you have set.
You can’t change the odometer; it is illegal to change the odometer. It must be functioning to inspect, register or sell the vehicle.
How to Read Car Gauges
After you identify what each of the gauges represents, you’ll discover that reading the dashboard gauges is easy. The speedometer is the only gauge that shows how fast you are going. In the United States, the speedometer only shows miles per hour (mph), but other parts of the world may show kilometers per hour (km/h).
The tachometer shows how many times the engine is rotating, or the revolutions per minute (RPM). The other gauges usually measure empty/full or low/high.
You will also see one or more warning lights that correlate with the appropriate gauge. If the light turns, you will want to check the associated gauge to see what’s going on.
For example, some warning lights indicate that you must stop driving right away, such as the oil pressure light.
However, some warning lights may give you a heads up that a problem may be coming such as the charging system light. Likewise, if the Check Engine Light occurs, you would want to check the system right away with a code scanner, to see what is wrong.