Can You Jumpstart A Car With A Bad Alternator?

Can You Jump a Battery if the Alternator is Bad?

Depending on the vehicle’s condition, you can jumpstart a car to give the computer system, fuel pump, and fuel injectors the zap of electricity it needs to drive it a short distance.

The alternator gives the car battery the life it needs to radiate energy into its critical components. That’s why it’s important to get it fixed as soon as possible. If you’re housing a bad alternator, you can only loan your battery power a few extra minutes. So I wouldn’t go revving your engine if I were you. Save that power like it’s your last Starburst.

Can a Car Run with a Bad Alternator?

Caution: Evasive answer approaching.

Unfortunately, there are too many factors to consider when answering this question, so it’s impossible to give a straight yes or no. But, here are some ideas to think about:

  • What does your battery’s health look like? – If it’s dying, the distance you drive will be shorter.
  • How damaged is your alternator? – If severe, you may as well stick that ‘L’ plate back on your car because you’ll be stalling a lot.
  • Does your car look like a Best Buy store? – Having other electrical systems in your car can put extra tension on your alternator.
  • What’s your vehicle’s date of birth? – A newer vehicle won’t have enough power to last as long on the streets as an older model. This is because a newer vehicle relies more on battery power.
  • Are you a Fast and Furious fanatic? – Your speed matters. Drive slowly and keep your RPM to a minimum to prevent your problem from worsening.

How Do You Tell If It’s Your Alternator or Your Battery?

More often than not, it’s the battery at fault when your engine doesn’t start. But how do you know the difference? Keep reading.


Dim dashboard lights or headlights

The condition of your dashboard lights and headlights will mirror your battery power. For example, a weak dashboard light means a weak battery. No dashboard light means a dead battery.

Engine won’t turn over

Put your friend with the good battery on speed dial because if your engine doesn’t start, you’ll need those jumper cables. If your engine starts but doesn’t start again later, then it’s typically the battery’s fault.

Old battery

Damaged battery terminals will prevent enough voltage from charging your battery. Severe damage may require professional assistance.

A warped battery

If your battery is looking like your stomach after a large meal, bloated and swollen, then it needs replacing.

There’s a strange smell

If you didn’t eat eggs for breakfast, then that strange smell might not be you. That rotten egg smell is sulfuric acid in disguise and usually means your battery is leaking.


Frequent engine stalls and cranking issues

If you can’t drive immediately, it’s usually because of a faulty alternator.

Headlights that are dimming or are too bright

If your lights are flickering between bright and dim, then don’t panic; it’s not a ghost. It’s your bad alternator failing to deliver power.

The battery is dead

Although this could just be a battery issue, it’s worth exploring other faults. Remember, a faulty alternator is what gives your battery its charge. So if your battery is dead, then the alternator looks like the number one suspect.

Electrical accessories aren’t working

A faulty alternator can cause electrical appliances in your car to stop working. However, your car’s computer has a pecking order of what to cut off first. This means your headlights may still work even when you’ve lost your music.

There’s a burning smell

Your alternator is under vigorous friction that can cause a burning smell. It could be because it’s overworked or because there are damaged and frayed wires.

What to Do Before Jumpstarting the Car

You wouldn’t fix a bad chair with dodgy screws. So do NOT call the friend with the bad battery. You want to make sure that the vehicle helping you is in good condition to maximize efficiency. This is because your battery is going to be the vampire that hasn’t fed in decades – draining more energy from the good battery than a usual jumpstart would.

Now that they’ve arrived (I hope they brought you a coat), make sure you have the good battery car close to yours. Take out the keys to BOTH ignitions.

Let’s get jumpstarted.

How to Jump a Car with a Bad Alternator?

Tools and equipment needed

  • A set of jumper cables
  • A friend with a good car battery

Step 1

  • Grab one red clamp and attach it to the positive terminal (+) on your dead battery.
  • Grab the other red clamp and attach it to the positive (+) on the other vehicle’s battery.
  • Grab one black clamp and attach it to the negative terminal (-) on your friend’s good battery.
  • Lastly, grab the other black clamp and attach it to the bare metal stud/bolt head in the engine bay of your car with the dead battery.

Step 2

Prepare for the longest five minutes of your life. Triple check that your car is switched off before triple checking the cables are properly secured. Then ask the friend with the donor car to turn theirs on.

Wait around 4-5 minutes, leaving the donor car running, and then attempt to start your vehicle. If it’s bad news, wait another 3/4 minutes before trying again.

Step 3

  • Remove the black cable from the car with the bad battery.
  • Remove the red cable from the bad battery.
  • Then, remove the red cable from the (good) other battery.
  • Lastly, remove the black cable from the (good) other battery.

Step 4

Your air conditioning, heating, CD player, phone charger, any of your car’s electronic accessories need to be turned off. These things are like leeches and will drain all the battery power.

Hopefully, it’s not raining because windshield wipers will also drain too much battery power. If the jump start goes well and your car starts, you’ll be at the nearest mechanic in no time.

How Long Will a Battery Last with a Bad Alternator?

Typically around 30 minutes, so avoid highway driving and head straight to the auto repair shop instead!

How Far Can You Drive with a Bad Alternator?

This all depends on your battery. Without a charged battery, it won’t be very far before you call a towing service.

Risks of Driving with a Bad Alternator

They may cause issues with your vehicle’s electrical systems

You could end up with sluggish charging ports, windshield wipers, and power windows.

Make it more difficult to start the engine

Not only might you not be able to start the ignition system, but you could stall mid-drive. This could be dangerous if you’re driving on high-speed roads.

Causes the battery to drain entirely

Without a working alternator, your battery voltage will disperse, and you’ll need a jumper car to save you.

How to Fix Alternator Problems

Car alternator repair

Don’t wait any longer! Go hungry if you must. Get your alternator fixed.

Where to buy new car alternators

I wish I could give you a solution to fix your alternator problem that doesn’t involve spending money. However, the more you drive your car with a bad alternator, the more money you could end up spending!

Why not buy a reconditioned one instead of one that’s brand new?

Author: DJ

Dave Junior is a hands-on automotive technician with experience in performing service, diagnostics, and repairs on domestic and imported vehicles. He enjoys writing and sharing his knowledge far and wide.

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