What Are the Gauges in a Car?

If you’ve ever looked at your car’s dashboard and wondered what all the gauges are for, you’ve come to the right place.  It can be confusing, especially for a new driver, to understand all the gauges in a car, but fortunately, they aren’t so complicated.  You’ll be speaking your car’s language before you know it.

Quick Answer

Not all cars have all of the same gauges, but many of them are universal.

  • The fuel gauge, which is on all cars, measures how much fuel is in your car.
  • The speedometer, which is also on all cars, measures how fast your car is going.
  • The odometer, which all cars must have, counts how many miles or kilometers your car has driven in its lifetime.
  • The temperature gauge measures the temperature of your engine coolant.
  • The oil pressure gauge measures the pressure of the oil that is moving through the engine.
  • The voltmeter measures the voltage of your car’s charging system.
  • The ammeter measures amperage going into or out of the battery.
  • The tachometer measures how quickly the engine is spinning in RPM.

Knowing the purpose of a gauge is important, but so is knowing how to read it.  Reading a fuel gauge correctly can help you to identify possible issues.

What Are the Gauges in a Car

When trying to read a gauge in your car, it’s best to know what you’re looking for.  This will allow you to recognize potentially dangerous readings.

Fuel Gauge

Every car should have a fuel gauge; it’s one of the most important gauges on your car.  Your fuel gauge tells you how much fuel (typically gas) your car has in it at any point, allowing you to see when you should refill your tank.

The gauge will have the letter F (for full) on one side and the letter E (for empty) on the other, usually with notches in between to aid measurement.

When you fill your tank, your gauge should start on the F and gradually move to the E as you use your gas.  Once your fuel gauge reaches E, most cars have about one to two gallons left, and you should get more fuel as soon as possible.

It is strongly recommended that you refill your tank once you have ¼ of your tank remaining, because otherwise your fuel pump may overheat, risking serious damage.

Speedometer

Another very important gauge, the speedometer should be present and working in every car.  The speedometer displays the speed of your car in miles per hour (MPH) or kilometers per hour (KPH), depending on where you are.

Knowing your speed is essential for obeying traffic laws and maintaining a safe driving speed.

Older speedometers will show a circular gauge with a range of speeds on it that a needle will point to, indicating your speed.  Modern speedometers, on the other hand, are usually displayed on an electronic screen, and will just show your speed as a number.

A speedometer may become inaccurate depending on the size of your tires, but can be recalibrated to account for that, so keep that in mind when replacing your tires.

Odometer

When buying a used vehicle, you may be looking to find out how many miles (or kilometers!) it has on it.  This is a measurement given by the odometer, which keeps track of the total distance your vehicle has been driven.

The odometer can be found in most vehicles and is often required in order to get your car registered.  A car with a very high number on its odometer may indicate that is more likely to have problems, so a lower number on an odometer is considered to be desirable.

For this reason, some people have been known to commit odometer fraud, where they alter their odometer to display a lower number.  This practice is highly illegal.

Temperature

An overheated engine can be a huge problem, which is why it’s a good idea to keep an eye on your temperature gauge.  This gauge measures the temperature of your engine coolant to monitor for overheating.

This is usually shown in the classic circular shape with a needle pointing at the current temperature, but can be shown in other formats a well, such as a bar.  One end designates a cool temperature, and the other designates a hot temperature.

While some temperature gauges show the temperature in degrees, most only have color coding (blue as cold and red as hot) and ticks to indicate measurement.  The gauge should start at the cool end and gradually increase without reaching into the hot end, if things are as they should be.

If your temperature gauge is getting into the hot end, you should immediately pull over and turn off your engine until it cools down, as an overheated engine can cause irreparable damage.

Oil Pressure

Although it is not one of the most common gauges, the oil pressure gauge can prove to be very useful in monitoring your car’s health.

This gauge measures the pressure of the oil being moved through the car’s engine in much the same way that a person’s blood pressure measures the pressure of the blood moving through their body.

Although the number can vary quite a bit, a normal oil pressure gauge should read between 20 and 50 PSI while moving, and can be much lower while idling.

Having very low oil pressure can damage your car in a matter of seconds, so if you see a very low pressure reading, turn off your car immediately to diagnose the issue.  Most cars will display a warning light shaped as a lamp when oil pressure drops to an unsafe range.

Voltmeter

One of the two types of gauges used to monitor a car’s charging system, a voltmeter measures your car’s charging system’s voltage.  It is very important to keep track of your car’s charging system.

Although you may not find a voltmeter in every car, it can tell you a lot about the state of your car’s electrical system.  A voltmeter will show a range of numbers, usually starting at 8 or 9 on the low end and ending around 16 on the high end.

If your car is working correctly, it should be at around 12.5 volts when the engine is not running, and between 14 and 14.5 volts while the engine is running, unless a heavy burden is put on it, such as using many battery-powered functions at once.

Your voltmeter should not remain under 14 volts for a significant period of time or ever exceed 15 volts.  Both of these may be signs of trouble and should be investigated immediately.

Ammeter

The other gauge used to monitor a car’s charging system is the ammeter, which measures the electricity flowing in and out of a car’s battery in amps.

An ammeter shows a negative to positive range of numbers, often from -50 to 50 with a 0 in the middle, although the range may vary from car to car.  If electricity is flowing into the battery, it will show a positive reading, and if electricity is flowing out of the battery, it will show a negative reading.

Typically, your ammeter should show a reading close to 0, although it will usually be a low positive number while your car is running.  It may show a higher number when your engine is first turned on, but it should go down quickly.

If your ammeter consistently shows readings above 10 to 20 amps with battery-powered functions turned off, you may have a weak battery.  You should also watch out for negative readings, because that means your car is being primarily powered by your battery instead of your alternator, and this is an issue that should be investigated.

Tachometer

While the tachometer is most useful for drivers of cars with manual transmissions, all drivers can benefit from monitoring this gauge.

The tachometer measures how fast your engine is spinning in RPM, usually in thousands, meaning that multiplying your tachometer reading by 1,000 should get you your engine’s actual RPM.

For manual drivers, if your tachometer is showing an RPM around 3,000 to 4,000, that means you should shift into a lower gear. Most car’s owner’s manuals should indicate at what RPM you should shift gears for maximum efficiency.

For automatic drivers, the tachometer is still helpful, as a very high RPM can be an indicator of a problem that should be investigated, such as a load that may be too heavy.

When you know how to read your car’s gauges, you know how to measure your car’s health.  Always keep an eye on your car’s gauges.

What Else is on My Dashboard?

Despite knowing what your gauges mean, there might be some other things on your dashboard that you’re not sure about.  Here’s a few common dashboard features:

Warning Lights:  There are a lot of warning lights that could appear on your dashboard for all kinds of reasons – battery light, engine oil light, and anti-lock brake system light, to name a few.  Fortunately, your owner’s manual should have an explanation of each one with pictures.  Even if you don’t still have your owner’s manual, a quick search of “car warning lights” should help you identify the light on your dashboard.  If you see an unrecognized light, identify it quickly, because it may be an indicator of a major problem.

Seatbelt Light:  Possibly the most obnoxious of all the lights is the seatbelt light, for the very simple reason that it is usually accompanied by a loud beeping sound.  If your seatbelt is not hooked up, the seatbelt light will light up on your dashboard, and the beeping will sound.  This can also happen if a passenger is not strapped in.  Cars typically use weight to determine whether you have a passenger in a seat, so if you place something heavy in a passenger seat, consider strapping it in to avoid the seatbelt light and sound.

Headlight Indicators:  These very simple lights show you whether you have your headlights on, and whether you have your high beams on.  In most cars, you will have a green light depicting two small bulbs facing each other to indicate headlights are on, and a (usually) blue light depicting one large bulb to indicate high beams.

This list is far from exhaustive, and only meant to get you started; if you see something on your dashboard you don’t recognize, look it up immediately, as it could mean trouble.

What Are Some Other Warning Signs?

There are a handful of ways to tell if something is wrong with your car aside from reading the dashboard.  Here are some signs that you might have a problem.

Odd noises from the engine.  Engines usually make all kinds of sounds when they’re running, and that’s normal.  However, pay attention to any sounds that seem to be out of the ordinary.  It’s best to be aware of how your car normally sounds so that you can identify any abnormal noises.  If you do, you should have it checked out by a professional who can diagnose the issue.

Grinding from your brakes.  Pay close attention to how your brakes sound and feel, both when you are using them and when you are not.  If something sounds or feels different with your brakes, it could mean a number of things, including the possibility that your brake pads need to be replaced.  If you notice any unusual sounds or feelings coming from your brakes, once again, take your car to a professional to check them out.

Any sort of leak.  Cars use a lot of fluids in order to operate properly.  All of the fluids used in a car are essential, so any sort of leak can be a major issue.  Watch out for dripping or puddles forming under your car, and if you see any, take your car to a professional as soon as possible.  Before you do that, however, you will want to rule out water as the possible culprit.  Check the color and odor of the liquid.  If you’re not sure, err on the side of caution and have it investigated.

What if My Gauge Might Be Broken?

Gauges can break for a number of reasons.  The course of action you should take depends on what the gauge is, but here are a few suggestions to get you started.

Figure out if it is really broken.  There are tests you can perform to figure out if your gauge is truly broken.  A quick search online about tests for the gauge in question should help you find what you need.  Also, if your gauge isn’t moving, it may just be stuck, not broken.  Do some research on that type of gauge to see if there is a way to get it unstuck yourself.

Decide if you need it.  This may sound lazy, but it is genuinely worth considering whether you truly need the gauge that is broken.  Consider its function, if you ever use it, and if you ever would use it.  Not all cars have every type of gauge, so it’s possible that the gauge in question is not necessary.  If you feel certain that you don’t need the broken gauge, then that’s that.

See if you can fix it.  If you do need the gauge, you want to save some money, and – more importantly – you feel up to the challenge, you can try to fix the gauge by yourself.  This may be a bit risky, so do be careful if you choose this route.  Do a lot of research before starting, read instructions, watch tutorials, etc.  If you can fix it yourself, you can save a lot of money and gain useful experience.

Take it to a professional.  If you need the broken gauge to work but can’t (or don’t want to) fix it yourself, you will have to have a professional fix it.  Look around, check reviews, and find the best professional in your area for the job.

Wrap up

Gauges can be very useful instruments for monitoring the status of your car, and even more so if you are able to read them. Hopefully now you know how to keep tabs on your car’s health and know how to tell if something is wrong.  Remember, a small problem can turn into a big problem, so don’t be afraid to consult a professional when you need to or when you’re uncertain.

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