The national cost for alternator replacement is between $152 and $768 with an average of $487

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In Ashburn, people who book through CarAdvise save $163 on average for Alternator Replacement. Lock in this price now.

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National average cost of a Alternator Replacement
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What is an alternator and how does it work?

The alternator functions as a generator that powers the electrical system and all of the electronics in your vehicle when the engine is running. It also serves to recharge the battery. The alternator is mounted on your engine and is driven by a serpentine belt that turns its drive pulley. Whenever your engine is running and the crankshaft is spinning, the serpentine belt (moved by the crankshaft pulley) runs the alternator. A built-in voltage regulator and rectifier ensure that the electric current remains constant and correct to operate your vehicle’s various systems. Although an auto electrical system runs on DC power, and an alternator generates AC power, the rectifier diodes within the alternator convert AC to DC. Without the alternator, your battery would quickly wear down from the current draw of all your vehicle’s electrical needs.

Signs that your alternator needs to be replaced

If your alternator fails when you are driving, a dashboard warning light (usually shaped like a battery or with the letters “ALT”) will come on. Not long after the warning light appears, the electric components of your vehicle will begin to lose power - the headlights, interior lights, audio system, and the like. The battery will try to keep them working, but it simply does not have enough reserve power to run everything for long. Eventually, your vehicle will stall because the engine needs the alternator to operate. Jumpstarting your vehicle will not correct the problem. Other signs of a bad alternator that happen if the internal pulley shaft bearing fails include grinding or whining noises that rise and fall with changes in engine speed. You might also notice advance signs of a bad alternator if your engine turns over slowly when starting, as if the battery is weak. A weak battery can be a sign of a bad alternator. A technician can also test the alternator to determine whether or not it is putting out the proper voltage.

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How is this service performed

How is a Alternator Replacement done?

To replace your alternator, a technician will first install a memory-saving device on your vehicle to sustain the presets in your audio and navigation systems as well as the memory settings for the vehicle’s computers. Next, the negative battery terminal is disconnected. Depending on your vehicle make and model, other engine components might need to be removed for access to the alternator. Other common steps for alternator replacement include

  • Relieve tension on the serpentine belt and remove the belt, noting its routing pattern around all of the pulleys
  • Disconnect the electrical connections to the alternator
  • Remove the mounting bolts attaching the alternator to the engine
  • Dislodge and remove the alternator
  • Install the new alternator in its place, re-route the serpentine belt, and replace any components that were removed for access
  • Connect the battery
  • Start your engine and check for proper output of the new alternator

OTHER QUESTIONS CUSTOMERS ASK

Do I need a new battery after replacing an alternator?
If your battery is relatively new and in good condition when your alternator fails, it might not need to be replaced. The problem is that excessive electrical current draw is placed on your battery when the alternator goes bad. The result is that your battery will weaken; the voltage will drop below its normal “full” level of 12.6 volts. After all, at 12 volts, your battery is only one quarter charged. It is considered to be “dead” below 11.9 volts. A bad alternator can also overcharge your battery and cause harm. If your battery is older or weak already, it will likely need to be replaced along with the alternator.
Will a bad alternator ruin my battery?
A bad alternator can certainly cause damage to an otherwise good battery. Overcharging, intermittent charging, and failure to charge (among other problems) can all lead to a damaged battery. On the other hand, a bad battery will not typically cause damage to the alternator.
What can damage an alternator?
There are a few conditions that can cause damage to your alternator besides component malfunction due to a defect. Jumpstarting your engine the wrong way with the cables reversed, for instance, can harm your alternator. So can allowing it to get extremely wet, as you might if you drive through water that is too deep. Connecting electrical accessories with an excessive current draw (i.e. stereo amplifiers) that exceed the rating of your alternator can also cause it to overload.

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