Alternator Gets Hot (Excess Electrical Load, Blocked Airflow, Belt Tension)

alternator gets hot

Alternators cannot remain cool. After all, they transmit a current that recharges the battery and runs the car’s electronics. Anything that generates electricity will produce heat. The harder the alternator works, the hotter it will become.

However, excess heat is dangerous. It can accelerate the alternator’s wear and tear, reducing its lifespan significantly. Mechanics blame alternator overheating on the following:

Excessive Electrical Load

The alternators in street vehicles have an average rating of 80 amps. That is more than enough to keep the car’s battery and electronics afloat. However, the alternators have their limits. They can overheat if you strain them:

  • Using Too Many High-Drain Accessories

Scott Heiman from ‘Which Car?’ has experienced this phenomenon firsthand. He was driving on the Sturt Highway (Hay Plain) in Australia when the instrument panel died. A mechanic blamed the alternator. It had shorted, blowing the fusible link.

They replaced the alternator and went back on the road. Alternators can easily last 150,000 miles. However, Heiman’s replacement 85A alternator failed within six months. A thorough inspection blamed overloading.

Heiman noticed that every port in the car was connected to an appliance. And on top of the phones and cameras, the alternator was accommodating a third fridge in freeze mode (to keep meat safe). The mechanic was unsurprised to learn that the second alternator had also failed.

Heiman solved this problem permanently by installing a stronger 130A alternator. This is why the experts at Car Care Hacks have warned against careless modifications. The alternator will overheat because it must work harder to run aftermarket lights, electric turbochargers, powerful stereos, and any other high-drain accessory you’ve added.

  • Using A Weak Battery

Two scenarios can strain the alternator to the point where it overheats. The first is a weak battery that overloads the alternator by pulling too much current. The rectifier diodes and slip rings will fail.

The second is an alternator that tries to charge a discharged battery. The alternator may remain in an overloaded state for an extended period as it attempts to charge the battery to the maximum rate.

Denso expects the diodes to burn out because of an open circuit (between the alternator’s output and the battery’s positive connections). The alternator will overheat and fail.

  • Using A Bad Alternator

A defective alternator cannot produce sufficient current to run all the electronics. Auto Farm believes that vehicles have consistent electrical demands. Therefore, even without additional high-drain accessories, your car’s electronics are more likely to strain and overload a worn-out alternator.

Issues With The Cooling System: Blocked Or Damaged Airflow

As was noted earlier, alternators are hot. They generate heat. But that doesn’t stop them from performing their task because they have a cooling system. First of all,  they have an aluminum casing, which elevates the alternator’s ability to dissipate heat.

Secondly, cars use vents to eject excess heat. If that wasn’t enough, alternators have fans that work with the vents to keep the component cool. Unfortunately, an alternator’s cooling mechanism has weaknesses. For instance:

  • Debris can clog the vents, preventing the heat from escaping. You can hire a mechanic to install a splash shield that keeps mud and moisture away from the alternator. You can also manually clean blocked air vents with a brush to improve the airflow.
  • The fan can fail. The alternator will overheat without it because it can’t stay cool when the car is stationary.
  • Liquid cooling systems in modern vehicles can develop electrical faults.

An alternator can still burn you if you touch it with your bare hands despite functional cooling systems. The cooling systems will prevent the alternator from overheating. They won’t make the component cold.

Belt Tension And Alignment: Impact On Alternator Temperature

  • The belt and the pulley create friction to drive the alternator using the power from the crankshaft. The belt drive system can fail because of frayed belts and damaged pulleys. Loose belts are just as problematic because insufficient tension disrupts the belt’s ability to drive the alternator.
  • A loose belt will slip. It can’t apply the correct tension. As the friction increases, so will the heat. The heat will accumulate on the belt and pulleys, accelerating their wear and tear and harming the alternator in the long run.
  • A tight belt is not necessarily better. It strains the bearings, leading to over-amperage in the motor. Additionally, excess tension will damage the diode rectifier.
  • Dreisilker Electric Motors recommends the Optibelt Optikrik. Their video shows consumers how to use this device to take a belt tension reading.
  • You can fix these problems by replacing faulty belts and pulleys. Although, you should leave this decision in a mechanic’s hands. They may fix this problem by tightening the belt, cleaning it, and realigning the pulley.

Faulty Or Failing Components That Can Cause Overheating

  • A battery can lead to overheating because it is discharged (the alternator works harder than usual to charge it), overcharged, or old and corroded (leading to a short circuit and blowing a fuse).
  • The alternator can overheat because the diodes have started storing heat after failing.
  • The alternator itself can fail because of poor grounding.
  • The alternator has a cooling fan that dissipates heat. When it sustains damage, the heat will accumulate.
  • Debris can block the alternator vents, preventing the heat from escaping.
  • The bearings can fail, creating friction in the rotor, which encourages wear and tear and leads to overheating. Alternators with bad bearings may vibrate incessantly.
  • Broken pulleys create tension and alignment problems. This disrupts the rotor’s functions, leading to overheating.
  • The alternator uses wires to transmit the power it generates. Those wires can wear out, increasing resistance, which, in turn, raises the amount of heat the alternator generates.
  • Many people know that high-drain equipment can lead to overheating by straining the battery. They don’t realize that damaged accessories can produce similar results. Their faults can compel these loads to pull more power than they normally do. 

Effects Of Hot Weather On Alternator Temperature

Generally, the ambient temperature has minimal impact on the alternator. The alternator’s functions won’t change in response to hot weather, at least not directly. Garage Wire has noted that temperatures under the bonnet can spike during heatwaves, particularly in modern vehicles because they have smaller alternators designed to generate a greater output capable of accommodating an increasing number of electronic accessories.

Hot weather may strain the alternator, especially when the cooling fan fails, and debris blocks the vents. However, hot weather is unlikely to kill the alternator in most vehicles. Your biggest concern is the battery.

Hot weather is more dangerous to batteries than cold weather. Millions of people get stranded all the time during the summer because of battery-related issues.

High ambient temperatures will accelerate the wear and tear in a battery. This is a problem because a damaged or defective battery will increase the strain on the alternator, leading to an overload and overheating.

Therefore, hot weather can indirectly ruin or lower an alternator’s efficiency. This is why regular maintenance is essential. Maintenance allows mechanics to fix cooling fans and clean blocked vents on the alternator.

Normal Operating Temperatures For An Alternator

100 – 180 degrees F. This is the average temperature. The alternators in some vehicles operate at higher temperatures. Others require lower temperatures.

Consequences Of An Overheating Alternator

  • The battery will die because the alternator cannot charge it. Overheating makes alternators less efficient. They must work harder to generate the same or lower output. Eventually, they will fail to attain the appropriate charging voltage, and the battery will drain. This is bad because the battery starts the car.
  • The lights will dim because the alternator’s output has reduced. It can’t maintain the correct brightness while simultaneously charging the batteries and running all the other electronic components in the car.
  • Some accessories will stop working altogether. Others will become slow and less efficient. For instance, the audio quality may deteriorate. It may also take longer to lower or raise the windows.
  • You will notice various noises originating from under the hood. That includes whining, grinding, growling, humming, buzzing, squeaking, and more.
  • The battery warning light will illuminate because the vehicle has detected an electrical issue.
  • You will smell burning rubber as the alternator’s parts wear out, including the belt and pulley.

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