Sometimes it’s difficult to tell whether or not you have an alternator problem or a battery problem, especially since the two are deeply intertwined. When the alternator goes bad, everything goes bad. The battery can operate on its own, but not for long. Can you jumpstart a car with a bad alternator?

You can jumpstart your car with a bad alternator, however, you will only make it as far down the road as the amount of juice your battery got from the jump lasts. Once the juice is gone, you’re on the side of the road again.

In other words, unless you want to spend the rest of your days getting a jump just so you can drive out to the mailbox and back, it’s time for an alternator change. And, unless your battery is brand spanking new, you’ll probably need to replace it as well.

Understanding the alternator and the battery

The alternator is the generator for the entire vehicle’s electrical system, with the battery taking up some of the slack, directly current here and there, while insulating the entire system from power surges and the potential damage they can create.

Alternators are built to last and, unless you own a Jeep Wrangler or a Ford (insert model here), you won’t often end up on the side of the road because your alternator called it quits. That being said, the alternator and the battery have to be durable, because many of your vehicle’s most critical functions absolutely depend on them.

  • Conserving enough energy to start the engine up
  • Insulating the vehicle’s electronic system from power surges
  • Electricity to the ignition system and starter
  • Alternator and battery work in conjunction to run your electronics

If the alternator is doing its job correctly, the battery will always have enough power left over—once you cut the ignition—to start the vehicle the next day, or whenever you decide to head down to Tastee Freeze for some fried pickles and onion rings.

Of course, if the alternator is doing its job and the battery dies overnight, you either have a bad battery or there’s a serious malfunction somewhere in your electrical system.

If you’re not an electrician, electricity and how it works can still be explained fairly simply. Electricity needs a path to travel and so long as there is something compatible with it to travel down, it will do so. Once you shut the electricity highway down, however, it stops in its tracks—like if you decided to snip the 12-gauge wire in your extension cord.

In a vehicle, there are many stops along the highway where electricity, generated by the alternator and distributed by the alternator and the battery, stops along the way, like convenience stores.

Sound systems, LCDs, power outlets, blinkers, headlights, and taillights are just some of the places where electricity stops along the way. The battery is designed to deliver the right amount of voltage at the right time, all of the time.

The battery shares this surge protection job with fuses, that are designed to break the circuit (the highway) if there is ever an electrical overload.

It’s also the storage device that releases enough power, when the key is inserted and the ignition turned, to juice up the starter, which begins the process of chemical combustion through spark plugs and fuel injection.

The battery doesn’t do all of this alone. When the vehicle is running, the battery and alternator power their various assigned systems in conjunction with one another, as the alternator keeps the battery powered up.

When the alternator fails, only the battery remains, quickly draining out its last resources as you drive down the highway until it reaches the point where it dies as well.

Dangers of jumpstarting a vehicle with a bad alternator

The act of jumpstarting the vehicle with a bad alternator won’t necessarily cause any damage to your car. The danger comes from driving the vehicle with an alternator that is no longer providing the right amount of voltage to the systems that it is responsible for.

A jumpstart is not going to do much for you with a bad alternator, as your vehicle is likely to break down again a mile (maybe two) down the road. It may be worth a shot if the mechanic shop is just down the road and you think you can make it on a solid jumpstart.

There are a few primary functions that the alternator is generally responsible for:

  • The vehicle’s power steering system
  • The water pump
  • The fuel pump

In many vehicles, the power steering system is operated electrically. When the alternator goes, you will usually get a battery warning indicator and the power steering system may go out as well. You can still operate the vehicle without it, but it’s much more difficult to turn the steering wheel and turn the vehicle.

The engine will shut down if your fuel pump and fuel injection system stop running. Both of these systems are electrically driven and can no longer function without the alternator. Without fuel, you have no combustion and without combustion, your vehicle will coast to a stop.

The water pump is often responsible for two things, pumping your coolant through the vehicle to keep critical parts at nominal levels, and turning the belts, which may or may not run several components, depending on the design of your vehicle and, very often, the age.

Older vehicles have clutch fans and the fan is operated by the water pump as well since all of it is tied into multiple belts.

Replacing your alternator

The joy of doing your auto repair jobs is almost as good as watching paint dry on a paint job you didn’t participate in. Since the average cost of repairing anything on your vehicle is up to $75 per labor hour, not including the cost of the alternator, you might want to do it yourself anyhow.

Of course, the worst part about the alternator is that it seems like the more advanced cars get, the more plastic they like to install over the top of it, and the alternator often gets moved farther down.

While we can’t give you an accurate breakdown on removing and replacing your alternator, due to the number of different cars out there, we can point you in the right direction.

  • Start by removing the battery from the equation by disconnecting the cables
  • Locate the alternator
  • Its usually located on the lower, right-hand side of the engine
  • There is a series of wires connected to it and you should remove them first
  • Locate the tensioner for your alternator belt and loosen it
  • Remove the belt
  • Unbolt the alternator and remove it
  • Reverse your steps to install the new one.

Disconnecting the battery is your priority. Not only will it save you from accidentally completing the circuit with yourself—which will be quite a shock—but it will also protect other electrical components from a surge of electricity.

Locating the alternator can sometimes be problematic since it is often below the belts and A/C compressor, towards the front of the engine, and on the right. Of course, that’s not always the case, but it looks like a generator/turbine turned miniature, so it’s difficult to miss.

The wires need to come out first, especially since the alternator is heavy and difficult to maneuver out of the engine compartment. If the wires aren’t removed, you may pull apart the wires or tear something up if you drop the alternator.

Locating the alternator pulley tensioner and removing the belt from the pulley is likely to be the most frustrating and labor-intensive task throughout the entire process. Just be patient with it and it will come along eventually. Be sure to have the right tools for the task and everything will go much more smoothly.

Once you’ve removed the alternator and replaced it with the new one, be sure to bolt in all of the wires exactly where they were before, as well as the bolts that hold the alternator to the frame. The last thing you want to do is wire something wrong and end up destroying the alternator you just purchased and installed.

The last step is to replace the battery cables on their respective terminals. You may have to jumpstart the vehicle again, even with a brand new alternator in there. An alternator doesn’t act on its own and a dead battery will need to be juiced back up.

Of course, once you charge the battery back up and crank the vehicle, the new alternator will go to work immediately, back to the job of operating the components that it’s supposed to as well as maintaining a functional level of charge on your battery.

Final thoughts

You can jumpstart your car as many times as you like and it will operate for a time. However, with a bad alternator, that time won’t last long. It’s best to only do so in emergencies or if you’re trying to get your vehicle down the road to the mechanic.

You can also DIY so long as you have the tools and are willing to sit through a few YouTube videos because an alternator change is one of the easier repair issues on a vehicle.