How Long To Let Car Run After Replacing Alternator?

When you install a new alternator, you would expect that you could start driving immediately.

That is not the case if you want a long-lasting alternator. It is helpful to consider certain things, like how long to let car run after replacing alternator.

what to do after replacing alternator

New alternators need to be treated with care when they are first installed. In this article, you will be able to understand what to do when you install a new alternator. We will look into some problems you may encounter after installing new alternator.

How long to let car run after replacing alternator?

After changing your alternator, the first thing to do is let your vehicle run just above idle. You should run for at least 10 minutes. Then switch off your engine and let the alternator cool.

Learning what to do after replacing alternator is a helpful skill for all. Although people typically neglect the safety of their alternator.

There are procedures to follow before fully using your alternator. Below are what to do after installing a new alternator.

1. Run your car for 10 minutes with a minimal electrical load above idle. It will warm up the alternator.

2. Shut down the car for about 15 minutes allowing the alternator to cool down.

3. Start the car again for another 10 minutes; you can turn on the AC/heater and other electrical components.

4. Stop the car and let the alternator cool again.

5. If you jump-started your car, you should let your car run for another 30 minutes.

So, does a new alternator need to charge? Generally, you do not need to charge a new alternator. However, if you have a new battery that isn’t fully charged or requires a jump start, you may. You can charge your batteries by leaving the car running for about 30 minutes.

What to check after a new alternator installation?

After replacing the alternator, several components must be inspected to ensure they are in good condition. For instance, having a bad battery may affect the alternator’s performance.

Below are some components you need to check after installing an alternator.

1. Check the battery

The first component you must check after installing a new alternator is the battery. A failing battery could cause an early failure of the alternator.

First, ensure that the battery is connected correctly to avoid complications. Then ensure the battery is fully charged and can carry the electrical components.

Also, perform a load battery test and ensure the voltage is within 13.5v-14.5v. And anything below means you have a low or bad battery

2. Check the fan and pulley

Another factor that could damage your newalternator partsis the fan and pulley. If not installed properly, they can cause a lot of vibration that could lead to a failed alternator. 

Also, a faulty fan will be unable to cool the alternator. This could cause overheating of the alternator. A damaged pulley can cause the serpentine belt to slip out of place. When this happens, the alternator will be moving at the wrong speed.

3. Check alternator fuse, wires and cable

Alternator fuse, Wires and cables play a vital role in the alternator. You want to inspect for any burnt smell, disconnection, damaged wirings, or other damages.

In addition, trace the wiring from the alternator to the battery, ensuring the wire is in good condition.

4. Check the alternator speed and voltage

The next step is to inspect the new alternator. You want to ensure the alternator speed and voltage are not below or under the threshold. Using a voltmeter, check the alternator speed and voltage. Begin by revving the engine; your alternator is bad if the voltage falls below 12.2v-14.5v. Also, if it is static, the alternator is bad too.

5. Confirm the hardware used in installation

Check that the proper hardware was used during the installation of an alternator. You can confirm with a technician if you need clarification on the hardware used. Ensure that the correct bolts, usually grade-6 bolts with hardened flat washers, were used.  

Why won’t my car accelerate after replacing the alternator?

If you notice your vehicle refuses to accelerate after installing a new alternator, the primary cause is a loose connection within the alternator.

Most modern vehicles rely heavily on electric current coming from the battery and alternator. If the voltage is insufficient or too high, it could affect the general functioning of the vehicle. For instance, some vehicles will not shift gears due to alternator problems or drained batteries.

Also, if the alternator is not given accurate output, it could cause your vehicle not to accelerate. The output of the alternator should not be too high or low.

Try and examine your alternator, and check the wires, drive belt, and output. If everything works fine, the issue is not from the alternator. It might be a transmission issue or oil leakage on the alternator.  

Do I need to reset the computer after replacing the alternator?

Resetting the vehicle’s computer system is not necessary after new alternators. However, the alternator is a significant change; as long as no modifications are done alongside the replacement, you may not need to reset the ECU.

You can if you reset the ECU after replacing the alternator. However, you may get little improvement in the alternator performance.

Furthermore, before you reset your ECU, note that some car manufacturers have recommended how to do so correctly. You can find this in your vehicle’s manual.


Installing an alternator can be tricky and quite expensive. However, it will cost you more when you do not know what to do after installation. People have asked, “Can a brand new alternator be bad” The answer is yes if you do not understand what to do before fully using the alternator.

Akindayini Temiloluwa

I am Akindayini Temiloluwa, an automotive expert writer and car enthusiast. I have over three years of experience in the automotive writing niche and have completed over 300 pieces of content from 50 projects. I have vast knowledge and skill in vehicle repairing, all mechanical work, car upgrades and maintenance. My goal as an automotive content writer is to simplify the most challenging concepts for my readers, help them self-diagnose what may be wrong with their vehicles and offer real value for their time.

Recent Posts