Car Gauges

by | Mar 18, 2020 | Best Practices

How to make sense of the dials and sensors

Cars come with a lot of gauges, especially on older models. Even newer model cars offer so many diagnostic numbers that they can confuse the most experienced drivers. To help you make sense of your dashboard gauges, here is a rundown of the six most important car gauges you’ll encounter.

What is the speedometer?

The most basic car gauge is the speedometer, the indicator that tells you how fast you’re going. But this gauge isn’t just impacted by your speed; your tires also play a role. Larger tires rotate at a slower rate, which means that if your tires are overinflated or you’ve added bigger tires to your vehicle, your speedometer will register a slower speed. That means that you should be aware you may be speeding even if your speedometer is at the speed limit.

Alternatively, smaller or underinflated tires rotate at a faster speed, meaning your speedometer may be saying you’re going faster than you actually are. That said, always pay attention to your tire pressure.

If you have any questions about your tires or car repair stop into any of HEART Certified Auto Care locations.

What is the fuel gauge?

Another important car gauge is the fuel gauge, and its indicators are very straight forward: F means “full,” and E means “empty.” But, of course, sometimes we’re too focused on the road to pay attention to our fuel gauge. Luckily, most cars have a warning light if your fuel goes too low. Always pay attention to this light, because driving on dangerously low fuel not only leads to potential breakdown but can lead to overheating and costly repairs.

What is a tachometer?

Here’s one that’s more obscure: The Tachometer. This measures your engine’s revolutions per minute (RPM). The higher end is typically color coded red; that’s not an area you want to hit. If your tachometer is in the red, that means your engine is rotating dangerously quickly, which can lead to damage and costly repair. Just as important, running at too high of a RPM also burns more fuel faster, decreasing fuel efficiency, straining not just your engine, but your wallet.

What is the temperature gauge?

You know how you put coolant in your car? The temperature gauge makes sure it’s working and lets you know when it’s not. Older model cars often have a gauge that spans from cold to hot (C or H), while many newer models simply have a light that illuminates when your car engine is running too hot. If your car is consistently too hot, or too cold, that means there’s an internal issue that could lead to potential damage. If your car’s temperature light turns on, visit one of HEART Certified Auto Care’s three convenient Chicago area locations. We’ll have you back up and running in no time. In fact, 98% of our service is done same day.

What is the oil pressure gauge?

Older models often have a dial displaying oil pressure, while newer models often have a little light that turns on when oil is low. Either way, if your oil pressure is low, it’s time to visit HEART Certified Auto Care. Oil is the lifeblood of your car — see our tips on oil maintenance here — and running with low levels can wreak havoc on your car engine.

What is the charging system gauge?

Measured in volts, and often 8-16, the charging system gauge monitors your vehicle’s electrical system. If it’s running on the higher end, that means you’re using more power; if it’s on the lower end, that means you’re using less power. If a light goes on, that means you have a problem with your car’s electrical system and should visit a trusted car repair shop ASAP. We of course recommend HEART Certified Auto Care, and so do others: we have over 500 five star reviews.

If you have further questions about your car gauges or any other car repair matter, call or stop by one of HEART’s three convenient Chicago area locations: HEART Wilmette, HEART Northbrook, or HEART Evanston.

Overview:

The minimum number of gauges on a passenger car dashboard are the speedometer and the fuel gauge. The most common additional gauge is the temperature gauge followed by the tachometer, voltmeter and oil pressure gauge. If your car does not have a temperature gauge, oil pressure gauge or charging system gauge, then you will have a warning light for these functions.

Speedometer

In the past, the most used of the gauges. The speedometer was usually driven by a cable that spins inside a flexible tube. The cable is connected on one side to the speedometer, and on the other side to the speedometer gear inside the transmission. Today, just about all vehicles have eliminated the cable and use an electronic sensor to measure wheel speed and send the signal to an electronically driven speedometer.

The accuracy of the speedometer can be affected by the size of the tires. If the tires are larger in diameter than original equipment, the speedometer will read that you are going slower then you actually are. On older vehicles, another cause for inaccurate speed readings was an improper speedometer gear inside the transmission. This can sometimes happen after a replacement transmission has been installed. On vehicles with electronic speedometers, the computer has settings to for speedometer calibration when necessary, to allow a technician to adjust for different sized tires. These calibrations usually require specialized equipment like diagnostic scanners to do these types of adjustments.

Fuel Gauge

Commonly used and self-explanatory, your car’s fuel gauge approximates the amount of gasoline remaining in your tank. In most modern vehicles, the fuel gauge will also include a warning light that will illuminate when gasoline levels are dangerously low. You should not continually allow fuel to reach dangerously low levels before refueling, because your car’s fuel pump is immersed in gasoline, which acts as a coolant for the pump. If fuel is low, the pump can be exposed to air and overheat, possibly leading to pump failure. Therefore, your car’s fuel gauge needs to be constantly monitored.

Tachometer

Tachometers calculate the speed your car’s engine is rotating while in operation and shows it to you in revolutions per minute (RPM). If the gauge reaches dangerously high levels, typically indicated in red on the tachometer, the engine is rotating at a high velocity, which can result in vehicle complications. The tachometer should be monitored, as it is related to both power output and fuel economy. Generally, the higher the RPM reading, the more fuel consumption and power the engine is outputting. Lower, consistent RPM levels on the tachometer indicate the engine is operating at an optimal level, resulting in better fuel economy.

Temperature Gauge/Light

What is the temperature gauge?

You know how you put coolant in your car? The temperature gauge makes sure it’s working, and lets you know when it’s not. Older model cars often have a gauge that spans from cold to hot (C or H), while new models simply have a light that illuminates when your car engine is running too hot. If your car is consistently too hot, or too cold, that means there’s an internal issue that could lead to potential damage. If you car’s temperature gauge turns on, visit one of HEART’s three convenient Chicago area locations. We’ll have you back up and running in no time. In fact, 98% of our service is done same day.

Dashboards differ on how they display the temperature of your engine coolant. Some cars include a gauge that measures coolant temperature and varies from cold (C) to hot (H), while others feature a thermometer that will illuminate red if your engine is dangerously hot. If the coolant temperature warning light appears or the temperature gauge reaches red levels, this indicates the coolant temperature has reached an extremely high temperature. Driving while these warning lights are engaged can cause extensive engine damage.

Oil Pressure Gauge/Light

What is the oil pressure gauge?

Older models often have a dial displaying oil pressure. Newer models often have a little light that turns on when oil is low. Either way, if your oil pressure is low, it’s time to visit HEART. Oil is the lifeblood of your car — see our tips on oil maintenance here — and running with low levels can wreak havoc on your car engine.

Another gauge type typically found in older cars is an oil pressure gauge or lamp. Not all dashboards will contain an oil pressure gauge; newer vehicles have an oil warning lamp to caution drivers the oil level is low. Oil pressure is vital to your engine’s performance, and its absence will result in severe engine failure.

Charging system gauge or warning lamp

The charging system is what provides the electrical current for your vehicle. Without a charging system, your battery will soon be depleted and your vehicle will shut down. The charging system gauge or warning lamp monitors the health of this system so that you have a warning of a problem before you get stuck.

When a charging problem is indicated, you can still drive a short distance to find help unlike an oil pressure or coolant temperature problem which can cause serious engine damage if you continue to drive.

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