Running a Car without an Alternator | 5 Things you Should Know

Is your car alternator dead? Are you considering driving to the nearest service station without a working alternator?

Well, you may be able to but there are a few important things you need to know to help you make the best decision whether to drive or not and to get as much mileage as you can without an alternator.

So, in this post, I cover several important points: when you should attempt to drive your car without an alternator, how to drive your car without an alternator, how long you can drive your car, and the risks involved.


#1. Can a Car Run without an Alternator?

Yes, a car can run without an alternator -whether dead or simply not connected or dead provided the battery still has sufficient power to start the car and to keep the engine running.

What your car will be running on?

When the car alternator is not working, the battery light will come on – to show that there is a fault with the charging system.

In this case, the charging source – the alternator is not there so no charging is taking place.

The car then relies on the energy in the battery to start and keep the engine running.

Since the battery stores limited power, the car’s electrical accessories and the engine will only work as long as there is available power from the battery.

This is because, with both the alternator and battery connected and working properly, the alternator is the first and main source of power.

If additional power is required, the battery supplies the extra power required.

You may want to read this post: Car battery light on and off – causes explained

#2. Should you Run a Car without an Alternator?

It is not advisable to drive with a dead alternator unless in case of an emergency and even then it should be for a short distance or else you risk the car stopping in the middle of nowhere when the battery runs out.


#3. Running a Car without an Alternator | How you can do it?

Starting the car is no issue provided the charge on the car battery can supply the required cranking amps for the engineer to start.

Make sure the battery is in good condition and fully charged as this largely determines how far the car can go.

To get as much mileage as possible, minimize the use of electrical accessories that consume the battery power.

Switch off any unnecessary accessories

  • sound system or radio
  • GPS navigation systems
  • heater (depending)
  • rear window defroster

Driving during the day (headlights not required) and in weather that does not require that you switch on a blower fan, wipers is better for minimizing power draw from the battery by the accessories.

Even then, there is power drain from the battery when the engine starts, powering fuel management systems, and from loads of sensors in modern cars, so the battery can only last so long.

#4. How Long a Car Run without an Alternator?

This really depends on the capacity of the car battery (Ah) or CCA, its state of charge, and how much power is being consumed by the accessories that are currently switched on in the car.

With a fully charged battery and power draw limited to engine management loads like ignition, fuel management only (headlamps, no sound system, and others switched off), a car can run for about 15- 30 min or longer, depending on the condition of the battery, car electronics -sensors, actuators.

When there is no more battery power, the car engine will stop running.

You may want to read: 6 Reasons why your car battery power may be draining and how to fix them

#5. Risks of Driving without an Alternator

When you drive the car without a working alternator, you face 2 main risks:

  • The car engine runs for a shorter time and you risk the car stopping in the middle of nowhere.
  • Limited time to use of essential electrical accessories – including the essential ones such as headlights, heater during cold weather.

These draw more power and the battery will last a shorter time and the car engine run for less.

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How Many Times Can You Start a Car without An Alternator

There is no one answer to this one – it depends on the capacity of the battery (Ah or CCA), its age and capacity to hold a charge, and the current state of charge on the battery.

Starting the engine puts a heavy drain on the car battery and reduces its state of charge.

You want to minimize the number of attempted starts and switch off any accessories that may be draining the battery because there is no alternator to replenish the lost charge.

Can a Car Run without an Alternator Belt?

A car without an alternator belt is as good as a car without the alternator connected or dead.

The belt couples the alternator and keeps it running using the power from the engine.

A car without an alternator belt can start provided the car battery has sufficient charge to start it and run for as long as there is enough power to run the essential electronics in the car – ECU, fuel management systems, and any others that may be installed in the car.

As soon as battery power is depleted, the car engine will stop running.

For more information on how to keep your car running for as long as possible without an alternator belt, check here.

Final Thoughts

You should only run your car without an alternator in an emergency.

Beware that you do that for a limited time, 15-30 min or longer depending on the condition of your battery, and its level of charge.

Once the battery power is used up, the car engine stops.

You can have your car running for longer by switching off non-essential accessories – or running your car when you do not need the high drain loads like the headlamps, blower motor.

But even then, know that you can only run it for a limited time.

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