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▷▷ 2021 ▷ how to repair ford f150 alternator, how to replace your alternator

4 julio, 2021

How to troubleshoot a Ford F150 alternator

Ford F150 alternators are numerous in styles and amperage, which are designed for a multitude of accessories and equipment. Ford has alternators with external and internal fans. They also have internal and external regulators. The amperage ranges from 90 to 215 amps. Alternators should always charge the battery to a minimum of 2.5 volts above base voltage, which is the battery voltage. With all electrical accessories turned on (lights, air conditioning, and radio), the voltage should be at least half a volt higher than the battery voltage.

how to repair alternator

Step 1: alternator fuse

Check the belt tension and the physical appearance of the belt to make sure it does not slip. Check the starter relay fuse and replace if necessary. Check the load fuse, if any. This depends on the year of the truck. The fuse block is fine on the driver’s side fender.

Step 2: alternator ford f150

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Turn on the ignition key but do not start the engine. Check for power to the large battery, plus the wire on the back of the alternator, connecting the black ground wire from the voltmeter to a good ground. Use the red wire to probe the terminal to which the large diameter wire is connected. There should be battery voltage at this post. If no voltage is indicated, check the fusible link under the starter relay in the same box as the fuses.

Step 3: what is the alternator fuse

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Look at the cover of the fuse box; illustrates the position of the starter relay. Look at the wires coming out of the starter relay at the bottom of the case; the wire with the wrinkles in the insulation is the fusible link. Check the voltage before and after the link, using the red probe of the voltmeter. If there is voltage before the fusible link and not after, the link is open and must be replaced. If there is no voltage in either location, the starter relay is bad.

Step 4: f150 alternator

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Place the voltmeter’s red positive probe and black ground probe on the corresponding battery terminals to check the battery before starting the truck. Record the base voltage of the battery, which should be approximately 12.75 volts. If the battery voltage is less than 12 volts, there may be a problem with the battery.

Step 5

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Start the engine and check the voltmeter. It will take a few minutes for the tension to stabilize. The voltage must be a minimum of 2.5 volts above the base battery voltage. This equates to about 13.8 to 14.5 volts. If the displayed voltage is less than 13.8 and the battery is good, the alternator is charging poorly. This means you have a faulty trio of diodes. Diodes are like one-way valves. They allow the alternating voltage (AC), which fluctuates back and forth in both directions, to move only in one direction, so you have direct voltage. When the diodes fail, the voltage and amperage drop. An alternator can work with a faulty diode; however, it will only charge the battery slowly and will not charge when the lights and air conditioner are on. If the alternator shows more than 15.5 volts, it is overloading, which means that the voltage regulator has failed. In this case, with a little mechanical ability, you can buy a new regulator, disassemble the alternator, and replace the regulator. If not, replace the alternator.

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Turn on the headlights, air conditioning and radio and increase the engine rpm to 2000. Read the voltmeter display. If the voltage is below 13.5 volts, a trio of diodes is bad. If the voltage is greater than 15 volts, the regulator is bad. The target voltage is 13.5 to 14.5 volts for a good alternator.


  • You need to understand the relationship between the battery and the alternator because one will not work properly without the other. A battery with a bad cell is like a soda can with a small hole in the bottom. The alternator will never be able to fully charge the battery. A battery with a bad cell can show 12 volts when charged; however, he will not hold office.
  • Not only will it not maintain its state of charge, but for each cell the amperage fails, the charge will decrease. A battery can show 12 volts with most cells bad, but it won’t have enough amperage to turn the lights on. A battery that starts the car 10 minutes after the engine is turned off but does not start the car a few hours later has a bad cell.


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