Can You Jumpstart a Car with A Bad Alternator? [Guide]

Published: 09/14/22 •  6 min read
Knowledge Panel

When your car’s alternator is faulty, you should replace it as soon as possible, but what if you can’t replace it right away. Your car battery is draining, which means you need a jumpstart to get the engine running again. Is it safe to jumpstart a battery with a bad alternator?

Your car can actually be jumpstarted with a bad alternator, and it will keep running for some time, though the battery is obviously going to die when the alternator eventually stops working. This is because your car can run on battery power alone until the alternator eventually stops working.

This trick isn’t recommended by any means, but it may be necessary if you just need to get a short distance away from your car. Jump starting the car with a battery can help a dead battery if the battery is low.

Since this car’s battery won’t be assisted by its alternator, a jumpstarted battery will go dead much faster than if it was properly charged. This effect can be accelerated if there is a high electrical load on your car, such as heating, phone charging, etc.

Contrary to popular belief, removing the jumper cables from the engine won’t stop the engine right away; it will keep running until the battery voltage falls too low for any electrical system to operate properly.

What Are The Dangers Of Jumpstarting A Car With A Bad Alternator?

Generally, if you are jump-starting correctly you should not experience any damage to the donor or recipient’s car, but it is always a risk. A car with a bad alternator also poses a significant danger if you have a newer car.

The alternator powers all the electrical components in your car. It also keeps the battery charged so that if the engine dies, you can use the battery to start it again. Alternators are designed to run at about 14.5 volts for a 12-volt system, although many Asian vehicles run at much higher voltages.

As most car owners know, the alternator is important in supplying power to the car’s electrical components, especially for newer cars. A lower volt signal from the alternator can cause components to fail in newer cars, such as:

Power Steering

Some vehicles are equipped with power steering. The power steering pump provides extra force to make steering easier. Steering becomes difficult without the assistance of the power steering pump, which may lead to maneuvering or steering quickly.

Fuel Pump

The fuel pump delivers fuel to the engine and is almost always electric. The engine will stop if the fuel pump fails to deliver fuel to the engine.

Electric Water Pumps

Your engine depends on the water pump to move water from the radiator and through the engine block, keeping the car running smoothly. The pump moves water to where it is needed to keep the engine cool. If your water pump fails, your car will overheat and you could cause serious, permanent damage due to this.

Although your car might shut itself off before anything serious happens, this is the safest way to prevent major problems. This issue can be devastating if the engine shuts off after a jumpstart, Do not try fixing yourself, it’s better to slowly pull over to the side of the road and call a tow truck.

How Far Can You Drive With a Bad Alternator?

There is no easy way to answer this question. Too many factors affect how long it’s safe to drive with a bad alternator and some of them are:

with a faulty alternator, you should expect it to run for around 20 minutes or 13–15 miles, which could extend more if you drive slowly while keeping your RPM low. If your car has just been jump-started or has a low battery, it would be surprising if your car can go for more than 10 minutes or 7-10 miles.

How To Jumpstart a Car With a Bad Alternator 

If you need to jumpstart a car with a bad alternator, you don’t have to do anything different but there are a few quirks to getting it right. You can use jumpstart cabl

es to charge the battery. It may take anywhere from two to three minutes to charge a battery and start a car.

It’s best to charge your car battery for at least 15 minutes before driving it. because the bad alternator will suck up much of the battery’s power and will no longer provide enough power to run the car, leaving you stranded.

Here are the steps to jump-start a car with a bad alternator.

1. Before Jumpstarting

  1. Make sure that the cars are separated and don’t touch each other.
  2. Remove the keys from both vehicles’ ignitions.
  3. Identify the positive and negative wires on the battery.
  4. Do NOT let clamps touch at any time.
  5. Do the steps below in order.

1. Attach Clamps

jump-start-a-car
Image Source: Progressive

2. Start Engine

3. Remove Clamps

4. Get The Alternator Fixed

Don’t wait to fix your alternator—it needs to be done ASAP. It can cost a lot to get an emergency repair, but it’s a problem that’s pretty simple to tackle yourself or leave with a trusted mechanic. Doing this sooner rather than later will save you from headaches later on and keep your car moving smoothly.