7 Reasons Your Car Won't Start in the Milwaukee Cold

What the Car Does When You Turn the Key

Start with your ears. The sound the car makes is the fastest clue you have, and it costs nothing. Find your row.

Those prices come off the Milwaukee Mobile Mechanic price list. The $150 call out covers the trip, a full scan and the first 30 minutes. If we do the repair, it comes off the bill.

Why won't a car start in the cold?

Cold slows the battery and thickens the oil at the same time. So the engine needs more power right when the battery has less to give. A battery that was weak in September often quits on the first hard freeze. Fuel and starter faults come next.

The numbers are brutal. AAA says a battery loses about 60 percent of its strength at zero, and is 35 percent weaker even at 32 degrees, per FOX 29 (January 10, 2017). In that same cold snap, AAA Mid-Atlantic took 1,309 dead battery calls in three days around Philadelphia.

Milwaukee lives below those numbers. The normal January low at Mitchell airport is 17.2 degrees, and the coldest morning of a typical January lands near 4.5 below, per the 1991 to 2020 normals on the Climate of Milwaukee page. The record is 26 below, set on January 17, 1982 and tied on February 4, 1996.

So a battery that tested borderline in October has nothing left by January. That's why the first deep freeze brings a wave of no starts all at once.

The 7 Reasons, in the Order We Check Them

1. A Battery That Was Already Weak

Cold rarely kills a good battery. It exposes a tired one. A battery that cranked fine at 60 degrees can lose more than half its punch on a zero degree morning.

Watch the dash when you turn the key. Lights that dim hard, or a crank that slows and stops, point here. A jump gets you going. It doesn't fix a battery that can't hold a charge.

2. Loose or Corroded Battery Terminals

A white or green crust on the posts blocks current. So does a clamp you can turn by hand. On a warm day the car may start anyway. On a cold one, it needs every amp, and a bad connection is enough to stop it.

Look before you jump. If a clamp moves, that might be the whole problem.

3. Oil Too Thick for the Morning

The W in 5W-30 stands for winter. The number in front tells you how cold the oil can get and still let the engine crank. The test points come from the SAE J300 standard, listed on the SAE J300 page.

Look at the bottom row. A 15W oil's test point sits right at a normal Milwaukee January's coldest morning. Use the grade on your oil cap or in your manual. Don't let a quick lube swap in something thicker for winter.

4. A Starter on Its Way Out

One click, bright lights, no crank. That's the classic starter sound. The RAC calls a click the most obvious sign of a bad starter, and notes that a jump won't help once it has failed.

Cold makes a worn starter work harder against thick oil. So a starter that was slow in fall often quits in the first cold week. On our price list a starter runs $320 to $700. Access sets the price, because some sit right on top and some hide under the intake.

5. A Dead Battery That Froze

A full battery almost can't freeze. A flat one can. The RAC says a fully charged battery freezes around minus 57 C, about 71 below, and a fully discharged one freezes around 0 C. That's 32 degrees. A normal January night here runs well below it.

So a battery that died on Friday can be frozen by Monday. Check the case. If it bulges or has cracks, don't jump it. Replace it.

6. Water or Ice in the Fuel

A car that cranks strong but never fires has a fuel or spark problem, not a battery problem. In deep cold, water in the fuel can freeze. The RAC notes that ice can block the narrow fuel lines and stop the engine from running at all.

Stop after two or three tries. More cranking just drains the battery and floods the engine. We tell people to keep the tank above a quarter in winter, so there's less empty space in it.

7. An Alternator That Never Caught Up

Short trips in the cold never put back what the start took out. The federal fuel economy site says a gas car can lose 15 to 33 percent of its mileage on short trips in the cold. Those same short hops leave the battery behind every day.

Then the alternator itself. The RAC says a car that dies right after a jump points to a bad alternator. Flickering lights and jumpy gauges are other signs. Keep jumping it and you'll kill a new battery too.

What should you do when your car won't start in the cold?

Turn off the lights, the heater fan and the radio. Crank for no more than 15 seconds, then wait before you try again. If the dash dims or it clicks fast, the battery needs a jump or a charge. If it cranks strong but won't fire, stop cranking and think fuel or spark.

That 15 second limit is straight from the manuals. Nissan's 2024 X-Trail owner's manual says not to run the starter more than 15 seconds at a time, and to wait 10 seconds before trying again. Longer cranking overheats the starter and drains what's left in the battery.

• Everything off. Lights, fan, radio, heated seats. Give the starter every amp.
• Check the clamps. A loose one can be the whole problem.
• Short tries. Up to 15 seconds, then rest.
• Jump it right. We say drive at least 20 minutes after, not around the block.
• Get it tested. A battery that needed one jump will need another.

Asked and Answered

What temperature is too cold for a car to start?

There's no single number. A healthy battery and the right oil start most cars well below zero. Weak parts fail first. AAA says a battery is 35 percent weaker at 32 degrees and about 60 percent weaker at zero.

Those AAA figures come from the same FOX 29 report. Going from 32 degrees down to zero costs another 25 points of the battery's full strength.

How long can you leave a car without starting it in cold weather?

A healthy battery can usually sit a couple of weeks. Cold cuts into that, because the battery has less to give when you finally turn the key. An old battery may not make it through one long cold snap.

We wrote a full guide on how long a car can sit before the battery dies. If a car will sit all winter, a battery maintainer is cheap insurance.

Do you need a block heater in Milwaukee?

Most gas cars with a good battery and the right oil start without one on a normal winter morning here. On the below zero mornings, a block heater makes any start easier. Some diesel truck makers recommend one below zero and require one below minus 20.

Ram's 2022 Heavy Duty owner's manual recommends the block heater below 0 F and requires it below minus 20 F. It says to plug in for at least one hour, on a grounded 110 to 115 volt outlet.

Should you warm up your car for 10 minutes in winter?

No. Modern cars don't need a long idle. The federal fuel economy site says most makers recommend driving off gently after about 30 seconds. The engine warms up faster while you drive.

Idling gets zero miles per gallon, as the fuel economy site puts it. Scrape the glass, start it, and go easy for the first few miles.

Will a car that won't start in the cold start once it warms up?

Often, yes, and that tells you something. A car that starts at noon but not at 7 a.m. has a weak battery, thick oil or a starter on its way out. The part is still failing. The next cold morning, it will do it again.

Get It Started Where It Sits

We come to the car, in the driveway, at work or on the street. The $150 call out includes a real battery, starter and charging test, not just a jump and a wave. If a part has failed, you get the price before we touch it. See the no start page, batteries and starting, or our full price list. Call (414) 877-8092.

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