Why does alternator wire get hot?

Asked By: Marylyn Eikeler | Last Updated: 29th March, 2020
Category: automotive auto parts
4.6/5 (4,336 Views . 26 Votes)
Most likely causes are; the alternator has been upgraded to a larger unit or the alternator voltage is excessive. High alternator voltage will allow it to produce too many amps and cause the alternator to run hot - too hot will result in premature failure (burning) of your alternator – like really quickly too.

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Besides, what causes a alternator to get hot?

The hot wire scent can be caused by an overheated alternator, one pushing too much power through the rotor and stator. Yeah, that's another possibility, thanks to the rubber belt that keeps the alternator going, as well as the rubber sheaths on the wires that connect everything in your electrical system.

Also Know, what are signs of alternator going bad? 6 Symptoms of a Failing Alternator

  • The indicator light.
  • Headlights are dim or flickering.
  • Other electrical failures.
  • Strange noises.
  • Car stalls or has difficulty starting.
  • Battery dies.

Just so, can I run a wire from the alternator to the battery?

In many other cars, the alternator output wire routes directly to the battery (or to the battery POSITIVE cable at the starter solenoid). And power-up wires to operate the dash area and electrical system will also connect at the battery.

Does an alternator smell when going bad?

Smell of Burning Rubber The scent of burning rubber or scorched wires sometimes indicate an alternator failure. Friction between a misaligned belt and the pulley will emit a smell of burning rubber. The burning wire smell can be caused by an overheated alternator.

29 Related Question Answers Found

Are alternators supposed to get really hot?

The battery measures 12.2 volts with the engine off, and the alternator puts out about 13.2 volts with the engine running. The alternator gets hot fast - uncomfortable to touch in just a minute or two - while the rest of the engine is still cool. After 5 minutes, it is untouchable.

What is the normal operating temperature of an alternator?

In the 1960's the typical underhood inlet cooling air temperature to the alternator was 90oC. By the 1980's this had jumped up to 110oC. Today, applications approach the 130oC range. But the demands on the thermal design don't stop there.

What does the W stand for on an alternator?

Although I can give you generic connections now (eg: the terminal marked B+ is the output, the terminal marked D+ goes to the charge light, the terminal marked W is the tacho connection) this presupposes your alternator uses the conventional markings.

How can I test my alternator?

Check the battery first.
  1. Turn off the car.
  2. Open the hood.
  3. Connect the voltmeter to the battery.
  4. Read the voltmeter.
  5. If the battery doesn't have enough voltage, either get the battery charged and re-test or try a different method for checking the alternator.

Why is my alternator smoking?


When an alternator fails, the bearings inside usually have failed to a point that causes them to whine severely and, depending on how badly they have failed, they may also smoke due to the excessive friction they create.

What would cause my alternator to catch on fire?

Another cause of alternator fires involves repairs. When an alternator is replaced, the connector should be examined. If the connector is not in good connection, it should be replaced as well. A damaged connector can cause wire melting and subsequently cause a fire.

What does R and F mean on an alternator?

The R and F terminals are the 'Reference' or voltage sense terminal and the 'Field' terminal.

What are the 3 wires on an alternator?

The three wire types in a three-wire alternator include the battery positive wire, the voltage sensing wire, and the ignition input wire. The battery positive wire connects to the starter. The voltage sensing wire connects to the battery, and the ignition wire connects from the alternator to the key switch.

Where does the alternator exciter wire go?

The wire is connected to the “L” terminal of the alternator. The exciter wire is used to turn on the voltage regulator. This wire, when unplugged, should have approx. 12.5 volts with the key on.

What are the two small wires on an alternator?


The two wires connected to the alternators are the positive and negative cables. When connecting our alternators use Fig 2 to properly connect these alternators. A jumper wire is supplied to connect the alternator (S) terminal to the (B+) terminal.

What is the exciter wire on an alternator?

An alternator is an auto part that transmits power from the fuel system to the battery for operating vehicle accessories, such as the radio, headlights and air conditioning fans. A wire called an exciter generates the voltage needed for an alternator to start working once a vehicle is started.

How do you check an alternator with a screwdriver?

Turn the ignition key to the “on” position, but do not start your car. The dashboard warning lights lights illuminate and the voltage regulator is activated. Repeat the test using the screwdriver. Place the metal end of the screwdriver near to the nut on the alternator pulley.

How do I know if my alternator has an internal regulator?

Check for regulator under the washer bottle and/or bracket on the driver side of the radiator support. If the pins are aligned like this "- -" on the side, then it is an internal regulated alternator. A 10SI will have a metal fan blade, or a 12SI, it will have a plastic fan blade.

What is the difference between 1 wire and 3 wire alternator?

“The 1-wire alternator only has a sense of what it is sending current to, which is the battery. The three wire alternator senses voltage at the fuse block and the ignition, and the alternator will then charge more to get all the systems up to power,” Overholser sums up.

What gauge wire should I use for my alternator?


Battery Wire Size per Voltage, Amperage Load and Length
System Voltage Amps 10-15 Ft
24 Volt 0-30 10 AWG wire
24 Volt 30-50 8 AWG
24 Volt 50-75 6 AWG
24 Volt 75-100 4 AWG

Are alternators fused?

There are certain models of car which have alternators dependent on a particular fuse to operate. However, these fuses can blow due to a power surge or simply from old age. Once that happens, the alternator will no longer charge the battery.

What is connected to the alternator?

There are two main components that make up an alternator. They are the rotor and the stator. The rotor is connected directly to the alternator pulley. The drive belt spins the pulley, which in turn spins the rotor.