Brakes, battery, wipers, lights and the seasons: what to notice and when to ask

The brake signs a driver can notice and the measurements to ask a shop for, the 12-volt battery's age and test, wipers and lights, and a season check with an emergency kit.

Brakes: what you notice and what to ask for Understand

In disc brakes, a brake pad (a block of friction material on a steel backing) is pressed by a caliper (the clamp that holds the pads) against a rotor (the metal disc that turns with the wheel). The pads and rotors wear a little with every stop, so they are wear items, judged by measuring them, not by a calendar. Physical principle Chevrolet says there are no specific mileage intervals for brake service, because wear depends on how and where the car is driven, and that its dealers inspect the brakes at every multipoint inspection (Chevrolet, About the brake system). Toyota Canada inspects them at every 8,000 km service on its Canadian schedule (Toyota Canada, 5 warning signs). Product-specific Your schedule may list a brake inspection; the wear itself shows up as a measurement or a sign.

The signs a driver can notice

You do not need to look at a brake to notice one of these. Chevrolet and Toyota Canada list them on their owner pages, and two AAA clubs add the sounds and smells.

Sources: Chevrolet; Toyota Canada; AAA Western and Central New York, smells and sounds; Car Care Council release, reprinted by AutoInc. (the council is an aftermarket trade group). Each source's "can mean" is a starting point for the technician, not a diagnosis. Some Chevrolet models also have an electronic pad-life monitor that reports wear on the dash. Product-specific

When you notice something, write it on the symptom log: what it is, which wheel or corner it seems to come from, when it happens (first stops of the day, hard stops, at speed), how often, and since when. That is the method Sounds, smells, leaks and feel teaches, and it is this manual's convention. This manual's convention

The brake warning light

The federal standard for dashboard lights fixes the brake system warning in red (49 CFR 571.101, FMVSS 101). On many cars the same light means two things. Ford calls it dual-function: the parking brake is on, or there is a brake fault or low brake fluid, and Ford says driving with it on is dangerous (Ford, warning and indicator lights). Hyundai says that if the light stays on with the parking brake released, the brake fluid may be low, and not to drive until it is filled (Hyundai, Warning Lights). Chevrolet says to pull over carefully if the light stays on while driving, and to have the car towed to the dealer if it stays on (Chevrolet, warning lights). Product-specific

The yellow ABS light is different. The anti-lock braking system (ABS) keeps the wheels from locking in a hard stop. Hyundai says that with only the ABS light on, the regular brakes still work, and that with the ABS and brake lights on together, you should avoid high speeds and sudden braking. Your owner's manual's lights page says what each light means on your car; Warning lights and codes sorts them into stop now, soon and information.

The measurements to ask for

A shop's inspection is where the brakes get measured. Two numbers and one condition let you read what it says:

• Pad thickness, in millimeters, for each axle. Ask for the front and rear readings, not just a color.
• The maker's minimum. A Berkeley shop's brake page says the company that made the car decides the minimum pad thickness, and advises asking for the pad measurement and the manufacturer's minimum specification (Art's Automotive, Brake Inspection). The shop reads that figure from its service information for your car. The gap between the reading and the minimum is what lets you plan.
• Rotor condition. Ask whether the rotors are above the maker's discard thickness (the minimum thickness at which a rotor is replaced), and whether the shop found pulsation, scoring or heat cracks. Chevrolet's dealer-service page says that on its vehicles rotors need not be resurfaced or replaced with new pads if there is no pulsation or vibration and the rotor is at least 1 mm above discard thickness (Chevy Certified Service, Brakes). That is one maker's rule. Product-specific

Write each answer on the recommendations sheet: the reading in "what they saw," the maker's minimum in "maker's limit," and the shop's color in "shop's mark." The same questions are on the questions for the shop sheet.

The colors are each shop's convention. Many shops send a digital vehicle inspection (DVI): a report from the shop's software with photos and a green, yellow or red mark on each item. The software vendors define those colors themselves, and they let shops rename them. Autoflow's help page defines green as good, yellow as requiring future attention and red as requiring urgent attention, and says an administrator can rename the statuses (Autoflow, Digital Vehicle Inspection). ARI, another vendor, tells shops they need written definitions, calls its own examples "not universal legal or safety definitions," and warns against using red to make a recommendation look more urgent (ARI, Digital Vehicle Inspection Checklist). Art's Automotive says a common pad gauge turns red at 3 mm and stays yellow up to 6 mm. So a color tells you how that shop ranks the item, and the measurement against the maker's minimum tells you where the part stands. Convention Ask "what does yellow mean at your shop?" and put the item through the four questions in Discussing recommendations.

Brake fluid, and cars that brake with the motor

Brake fluid is the hydraulic fluid that carries the pedal's force to the calipers. It absorbs moisture: the federal brake fluid standard requires every container to warn that it be kept tightly closed to prevent absorbing moisture, and that contamination may result in brake failure (49 CFR 571.116, FMVSS 116). Physical principle That is why many makers change it by time, and the intervals differ a great deal: Honda's Minder schedule replaces it every 3 years if the Minder has not called for it sooner, the 2025 Hyundai Sonata every 48,000 miles or 48 months, Tesla tests it every 4 years, and the 2025 Toyota Camry schedule inspects it without a replacement interval. Those examples, and how to put yours on the schedule sheet, are in Oil, fluids and filters.

Hybrids and electric cars slow down partly with regenerative braking: the motor works as a generator and turns the car's motion back into charge. The Department of Energy's Alternative Fuels Data Center says brake wear is significantly reduced as a result (AFDC, Maintenance and Safety of Electric Vehicles). Reduced is not ended. Tesla's maintenance page says brake pad replacements are rare, and asks owners on salted roads to have the brakes cleaned and lubricated every year or 12,500 miles (Tesla, Vehicle Maintenance). Product-specific Hybrids and electric cars covers what that means for the schedule.

The 12-volt battery: its age and its test

The 12-volt battery starts a gasoline or diesel engine and powers the lights and electronics when the engine is off. Hybrids and electric cars have one too, beside the high-voltage battery that drives the car; Hybrids and electric cars covers that pair. The charging system is what keeps the 12-volt battery charged while the car runs; on a car with an engine, its main part is the alternator, a generator driven by the engine.

How long batteries last, and why heat matters

AAA Oregon/Idaho says most batteries have a three- to five-year service life and calls heat the number one cause of battery failure and reduced battery life (AAA Oregon/Idaho, car care tips for extreme heat). AAA South Jersey explains the mechanism: heat speeds evaporation, corrosion and sulfation inside the battery, and fall is a common time for a battery to fail after a hot summer (AAA South Jersey, how heat wrecks your car battery). Physical principle A battery that dies on the first cold morning may have been weakened in August. AAA Oregon/Idaho adds that a faulty alternator is one of the most common causes of battery failure, so the charging system should be tested along with the battery.

When to test, and who tests

The default here is AAA's: have the battery tested once it is three years old, and every year after that (AAA, Roadside Breakdowns Preventable with Proper Maintenance, 2015). In the same release, AAA reported that two-thirds of the drivers it surveyed had not had a battery tested before it failed. If you test once a year, doing it before winter puts it in the same visit as NHTSA's winter advice to have a mechanic check the battery, charging system and belts (NHTSA, Winter Weather Driving Tips). Your owner's manual may give its own battery inspection item; where it does, it governs. Convention Other sources time the test differently; the comparison is in In depth.

A battery test is done with a tester at a shop or a parts store that offers it, and the result is a reading of the battery's condition and the charging system's output, not a guess from the battery's age. Write the date, who tested it and the result on the car facts sheet, which has a line for the install date and the last test. If the shop recommends a replacement, ask for the test result in writing, as for any other recommendation. Ask the authority

Finding the install date

Look for a date or install label on the battery, check the invoice or the service log, or ask the shop that installed it. If none of those give a date, write "unknown" and ask for a test at the next visit. An unknown date is worth recording as unknown: it tells the next person that the question is open. The charging light on the dash is the car's own warning about this system: Hyundai says it can mean an alternator or charging fault and to have it inspected as soon as possible, and Ford says to switch off unnecessary electrical loads and see a dealer.

Jump-starting. NHTSA's and Ready.gov's emergency kits both include jumper cables. How to connect them, and whether your car permits a jump, is in your owner's manual; follow it exactly, and where your manual says to call for help, call. This manual does not teach jump-starting beyond what your owner's manual describes. Hybrids and electric cars have their own instructions there.

Wipers, lights, belts and hoses

Wipers and washer fluid

Makers and trade groups give different wiper figures. The 2025 Toyota Camry's maintenance guide inspects the wiper blades every 5,000 miles and gives no replacement interval (Toyota, 2025 Camry Warranty and Maintenance Guide). The Car Care Council, an aftermarket trade group, says to check and change blades about every six months (Car Care Council, Car Care Tips). NHTSA's winter page says to replace worn blades and to use a winter washer fluid. Product-specific The default: inspect the blades when your schedule says, and replace them when they no longer clear the glass. Check them by running the washer with the car parked and watching what the blades leave on the windshield, front and rear. Test it Top up washer fluid where your owner's manual shows the reservoir.

Lights: a walk-around with a helper

Several of a car's lights are out of view from the driver's seat, brake lights above all. The easiest check takes two people: one in the seat working each switch, one walking around the car calling out what lights. Ready.gov's list of things to have a mechanic check includes lights and hazards (Ready.gov, Car safety). Check, in order:

• Low beams and high beams (the high-beam light on the dash is blue or green under FMVSS 101).
• Turn signals, front, rear and side, left and right; and the hazard flashers.
• Brake lights, including the center high-mounted one, with your helper behind the car while you press the pedal.
• Reverse lights: follow your owner's manual if it describes a safe way to check them, or ask the shop to.
• Tail lights, the license plate light, and fog lights if the car has them.

Write the date and anything that did not light on the schedule sheet or the symptom log. Whether you change a bulb yourself depends on your owner's manual: if it describes the job for the owner, follow it; if not, it is a shop job. Grouping the walk-around this way is this manual's convention. This manual's convention

Belts and hoses

Belts drive parts such as the alternator, and hoses carry coolant. Where your schedule lists them, they are inspection items with a mileage or a visit. NHTSA's winter page asks a mechanic to check the belts. Two signs come up in the sources: AAA Western and Central New York says a squeal when accelerating can be the serpentine belt, and the Car Care Council links a burnt-rubber smell to slipping belts or a hose rubbing a pulley, and says not to reach into the engine bay when it is hot. A sound or smell goes on the symptom log; Sounds, smells, leaks and feel covers how to describe it.

Seasons and trips: the season check, the kit and carbon monoxide

NHTSA counts 365 fatal crashes and an estimated 24,383 injury crashes in snow or sleet in 2024. Its winter page and Ready.gov, from FEMA, give the two federal lists for getting a car ready. We group their items, and a few from earlier sections, into a season check: a short list to run before winter, before summer heat and before a long trip. The grouping is this manual's convention; the items and their sources are not. This manual's convention

Each item's interval, where your owner's manual gives one, comes from the manual. The season check adds timing, not new service. If the shop's list for a winter visit includes items that are not here or in your schedule, put them through the four questions in Discussing recommendations.

The emergency kit

The two federal lists overlap. Pack the items both name first.

Sources: NHTSA, Winter Weather Driving Tips; Ready.gov, Car safety. A copy of the car facts sheet with the roadside assistance number, printed from the car file, fits in the glovebox with the kit.

Carbon monoxide

Carbon monoxide (CO) is a gas in engine exhaust that CDC describes as odorless and colorless. CDC counts more than 400 US deaths a year from unintentional CO poisoning not linked to fires. For cars, CDC gives three steps (CDC, Carbon Monoxide Poisoning Basics):

• Have a mechanic check the exhaust system every year. CDC says a small leak can build up CO inside the car.
• Do not run a vehicle in an attached garage, even with the garage door open.
• If you ride with only the tailgate open, CO can be drawn inside; open the vents or windows.

NHTSA adds the stranded-in-snow steps: stay with the car, clear snow from the exhaust pipe, and run the engine only sporadically, not for long periods with the windows up. A ticking sound with an exhaust smell, which AAA Western and Central New York says to have looked at right away, goes to the shop.

See it: Priya's pads, Sam's battery, Gloria's winter See it

• Chevrolet, About the brake system: the brake signs a driver notices, and why there is no mileage interval.
• Art's Automotive, Brake Inspection: one shop on why a gauge's color and the maker's minimum differ, and what to ask for.
• NHTSA, Winter Weather Driving Tips: the winter kit, the vehicle checks and what to do when stranded.
• CDC, Carbon Monoxide Poisoning Basics: the yearly exhaust check and the garage rule.

Practice: the walk-around with a helper Practice

Minimum: the battery's install date (or "unknown, test at next visit") on the car facts sheet; the wipers and every outside light checked with a helper and dated; a dated brake note on the symptom log, even if it says "nothing noticed." Time: about 30 minutes, with a helper for about 10. Materials: a helper, your owner's manual, a flashlight, the battery's invoice if you have one, and the car facts, symptom log, schedule and questions for the shop sheets (or paper). For the season check, the kit items you already have.

Work with the car parked on level ground, the parking brake set, out of traffic. Leave the battery cables and terminals alone, and keep hands out of the engine bay while the engine is running or hot.

1. Date the battery. With the engine off and cool, find the battery where your owner's manual shows it and look for a date or install label, without touching the terminals. Check the invoice or service log too. Write the date on the car facts sheet, and the month it turns three years old.
2. Check the lights. Your helper stands outside while you work each switch: low and high beams, each turn signal, hazards, brake lights (you press the pedal), tail and plate lights, fog lights. Ask the shop to check reverse lights if your manual does not say how to check them safely. Write the date and anything out.
3. Check the wipers. Run the washer and wipers, front and rear, and look at what they leave on the glass. Note streaks or missed patches, and top up washer fluid where the manual shows.
4. Write the brake note. On your next few drives, notice the first stops of the day and any hard stop. On the symptom log write what you noticed, which corner, when, how often and since when, or "nothing noticed" with the date.
5. Add the questions. On the questions for the shop sheet, add: front and rear pad thickness in millimeters, the maker's minimum, rotor thickness against discard, and a battery and charging system test if the battery is three or older or its age is unknown.

Your car Your car

Check your work Check your work

Criteria

• Does the car facts sheet have the battery's install date (or "unknown"), and the month it turns three?
• Is there a dated record that every outside light and both sets of wipers were checked, and what failed, if anything?
• Is there a dated brake note on the symptom log, written as what, where, when and how often?
• If a shop has inspected the brakes, does your sheet hold the pad readings in millimeters and the maker's minimum, not only a color?
• If winter or a long trip is coming, is the season check marked with who does each item, and is the kit in the car?

Worked example

Priya's recommendations sheet reads: front pads 3 mm (shop's yellow), rear 6 mm (green), maker's minimum read by the shop, rotor thickness asked for; decision "not now, recheck at next oil change, about 105,900." Her symptom log says "brakes: nothing noticed" with a date. It passes: the decision rests on measurements against the maker's figure, and it names the recheck that settles it. Sam's car facts sheet reads "12-volt battery: install date unknown; test at next visit," and their schedule sheet has the yearly brake cleaning for salted roads. That passes too, because the unknown is written as unknown with its route to an answer.

Common mistakes

• Reading the color as the measurement. Yellow at one shop is red on another shop's gauge. Ask for millimeters and the maker's minimum.
• Waiting for grinding. Chevrolet and Toyota Canada both say the squeal comes from wear indicators built to warn you earlier; grinding, Toyota Canada says, can mean metal-on-metal contact.
• Replacing a battery on age alone, or not testing it. Age tells you when to start testing; the test tells you its condition.
• Checking brake lights alone. You cannot see them from the seat; use a helper.
• Warming up the car in the garage. CDC says not to run a vehicle in an attached garage even with the door open.

What is still unresolved

What a brake sign means on your car is settled by a technician's inspection, and whether a brake job is needed now by your decision with the measurements in hand, using the four questions in Discussing recommendations. A battery's condition is settled by a test, not by this chapter. What a dash light means on your car is in your owner's manual and in Warning lights and codes. How to describe a sound or smell is in Sounds, smells, leaks and feel; the 12-volt battery and brakes on a hybrid or electric car are in Hybrids and electric cars; and tire checks for the season are in Tires.

Knowledge check and scenario

Checklist

• The car facts sheet has the battery date, and the symptom log or schedule sheet shows the brake, wiper and light checks with dates.
• I know the month my battery turns three, or wrote "unknown, test at next visit."
• I checked every outside light and the wipers with a helper.
• The questions for the shop sheet asks for pad thickness in millimeters, the maker's minimum and the rotor condition.
• I ran the before-winter season check and packed the kit. (Go deeper; optional)
• A yearly battery test and exhaust check are on the schedule sheet. (Go deeper; optional)