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Alternators are expensive. If your’s is failing, you may be tempted to run your car without one. You’ll likely want to know if it’s possible, dangerous, and will cause more damage to your car.

Cars generally run without an alternator until the battery dies, which may be only 5 minutes. Many systems rely on alternator power, including the water pump. Without this, the car will overheat and could damage the engine. 

What Is An Alternator?

Your car’s alternator charges the battery so that when you stop and need to start your car again, the battery has enough charge to turn the starter and get the car going. Its other job is to power all electrical systems when the car is being driven.  

Contrary to what many think, the alternator does this, not the battery. The battery’s job is to start the car. In the past has been called a ‘starting battery. ‘

The alternator is a clever device it turns one type of current called alternating current into direct current, which is what all your car systems need to run on. 

Can A Car Work Without An Alternator?

Relying on the battery may work in the very short term, but you’ll have to find a way to continually charge the battery as it’s not designed to provide power when the car is running. That’s the job of the alternator. Even an alternator with a reduced output is better than none.

Power steering may be unresponsive, windshield wipers may not work, and air conditioning will quickly drain the battery. 

If you decide to drive your car without an alternator, turn off or don’t use all systems that run from electricity. Don’t use the radio, electric windows, the blower, or heated screens.

Eventually, the battery will go bad, and you’ll have to replace that and the alternator. 

Can a Car Start Without an Alternator?

The alternator plays no part in starting a car. So the answer is YES. As long as the battery is fully charged, the vehicle should start.

However, if the alternator is bad, it will not have been charging the battery as you’ve been driving your car, so it’s unlikely that the battery will have enough juice to start your vehicle, in any case.

If you’ve charged the car battery with a charger overnight, you’ll have put power into it to start your engine.

You could do this for a few more days, but it’s going to be inconvenient, will only be okay for very short journeys, and you’ll risk damaging your engine and other electrical systems. Therefore, it’s not advisable. 

Colder climates drain batteries quicker – that’s why you’ll see more winter breakdowns on driveways – so if it’s winter or cold out, your battery may have less charge to get your car started.

How Long Can a Car Run Without an Alternator?

You can drive your car for ten minutes before the battery charge runs out. This is dependent on three things.

How healthy the battery is to start with. 

Batteries, on average, have a seven-year life span, but this can shorten if they are overcharged – often by a bad alternator – or operating in colder climates. 

If you have no alternator, you’ll only get a very short distance in a car with a bad battery.

How many times it takes to turn the starter motor to get the engine to fire. 

You’ll need your car to fire quickly so that more power remains in the battery to power it as you drive. Each turn your engine makes will lessen the remaining power. 

If your battery is struggling to turn the starter motor, then you’re not going to get very far. This is likely if you haven’t fully charged your battery before starting it.

What other are electrical components being used during the journey?

The alternator powers your car’s fuel pump, but if you also have the air con, radio, wipers, and blower on or are using your electric windows, the charge your battery is holding will drain away quickly.

Turn off everything you can to preserve the charge in the battery.

We go into how long a failing alternator may run a car in more detail How Long Can You Drive A Car With A Bad Alternator?

AC puts failing alternator under more strain

What Are The Risks Of Driving With A Bad Alternator?

Your car will eventually break down, but you’ll not know when or where it will happen. It could be in a line of traffic or when you need to be somewhere important. It’s far better to get your alternator repaired or replaced at a time to suit you rather than wait for the alternator to die completely.

You can and probably will cause further damage to other car systems. Firstly, as we’ve discussed, your car battery could be damaged beyond repair if the alternator overcharges it.

Or, if the battery is fully drained, it can stop charging correctly in the future. You may have to replace the battery and the alternator if you don’t get the alternator fixed as soon as possible.

Depending on your car, the alternator belt is also used to power other systems. The water pump is needed to keep your engine cool. It does this by pumping hot water from the engine to the radiator.

You could cook your engine if the belt is not powering the water pump. If you do, this is costly, and you may need a complete engine rebuild. 

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How To Tell If Your Alternator Is Going Bad?

The first telltale sign that your alternator is failing is that you will have real difficulty starting your car in the morning. One of your alternator’s jobs is to recharge the battery as your car is running, so that the next time you come to start the car, the battery is fully charged and has no difficulty providing enough power to send to the starter motor, which in turn starts your car.  

You may have noticed a reduction in the efficiency of your battery and noticed that the car crank turns slower when you turn the key than it did a few mornings ago. This is a sure sign that your alternator is not charging the battery correctly

The second sign the alternator is failing is that when you are driving, electrical components do not perform as you expect or not as well as they used to.

Have you noticed that your air-conditioning, heated seats, blower, headlights,  electric windows, and seats are not performing well? A good indicator is that the more systems you use, the less well they perform because the alternator is struggling to provide power to all the systems. 

The battery lights will almost always come on when the alternator isn’t being charged effectively.

Worried about your bad alternator smoking? Read our guide here Alternator Smoking Dangers [TROUBLESHOOTER GUIDE]

What To Do When Your Alternator Starts Going Bad?

It is tempting to leave a failing car part until it fails completely, but you should not do this with the alternator.

Your alternator will decide to quit on you at the most inconvenient time. It could be when you are in a queue of traffic or miles away from home. Either way, it’s going to be inconvenient and costly.  

Far better to get your car to a car shop before this happens because sometimes alternators can be salvaged and are worth repairing. You will also have time to plan your day and travel arrangements in advance.

A bad alternator can cause the voltage regulator to go bad, and this can send unchecked voltage to other systems under the hood. It is not unheard of for bulbs to blow and wiring to melt when the voltage regulator on the alternator goes bad. Bad alternator diodes may stop converting the current too.

By putting off a repair or replacement, you are putting other car systems at risk that could run into repair bills in the thousands of dollars.

Alternator Hot To Touch? 7 Causes of A Hot Car Alternator – Troubleshooter Guide

If you have to run your car with a failing alternator, it’s best to stay local and avoid queues and highways. 

It sounds obvious, but I will mention it anyway. Take provisions with you. Food and drink in case you become stranded at the side of the road and ensure your phone is fully charged because if you usually charge it in the car, this may not be possible for you with a bad alternator.

Can a Diesel Run Without an Alternator?

There is no real difference between petrol or diesel-powered car.

If you have a battery voltmeter on the dash, keep a close on this, as once it drops below 9 volts, you’re almost out of power.

Modern diesel cars are more complicated than petrol cars – they used to be the other way around – and have many sensors and valves. If one sends a signal back to your car’s ECU outside its acceptable parameters, it’ll either give you an engine warning light or stop. 

Of course, if you’re in a position to change over to another fully charged battery, swap it over. Like most people, it’s unlikely you’ve got a fully charged spare battery to drive around with inside your trunk.

Always be mindful of other damage you could be doing to other systems, especially the cooling system and water pump.

Will Older Cars Run For Longer Without An Alternator?

Older cars generally have fewer electrical circuits demanding power all the time. Newer cars are great and have features that keep us warm and comfortable. 

Older cars with less power-hungry systems will take less juice from the battery – remember the alternator is now out of the game – and therefore should mean they’ll drive for longer as power isn’t needed for sensors and computers, only lights and wipers etc.

This assumes the older car battery was in good condition before the alternator went bad. 

Can a Car Run on the Alternator Alone?

The alternator provides all the power the car needs once it has started. It turns pulleys, runs the water and fuel pump, and gives the power to run air conditioning, blowers, windshield wipers, and heated seats.

The battery is often referred to as the “starting battery.” Its job is to have enough power to turn the starter motor, and once it’s done, it’s redundant until the car needs to be started again. 

As the alternator is working, not only is it providing power for all the functions above, but it is also charging the battery, 

This ensures – if the battery is not itself bad- there is enough charge in the battery when it is called upon to start your car again.

How Many Times Will Your Car Crank Without an Alternator?

This is the $64,000 question and is impossible to answer with real accuracy. It all depends on the quality of the battery and the charge left in it when the alternator went bad.

The battery has to turn the starter motor, which turns the engine’s crankshaft. 

This requires a lot of power. 

If your car is regularly serviced and you have replaced fuel injectors, spark plugs, and other filters on time, it’s likely that your car normally starts quite well in the morning with very few turns of the crank.

If, however, your car is badly maintained and takes more than a few turns of the key to get the starter going then you will use the battery charge more quickly. 

In Conclusion

Your car needs both an alternator and a battery. 

Without a battery, your car won’t start, so the alternator can’t turn to power all the components needed to operate a driven car. – if you can jump-start the car – the alternator should work fine.

Without an alternator, your car will start but won’t provide all the power needed to operate the vehicle. It may drive for a short distance but then pun out of power. It may cause major mechanical and electric faults in your car.

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