Amperage is a term to describe the rate of flow of electric current. It is measured in amperes (A). To find out what amperage your alternator is, you must first understand the relationship between volts and amps. Volts are the capacity of a given electric current, and amps are the current’s power amps. If you don’t have enough volts, it could cause serious and permanent damage to your automobile. Without enough current electrical components, several can starve and burn out.
Consider the size and location of your particular alternator. It will help you narrow down the numerical possibilities. Alternators vary greatly in size and appearance. For example, some cars have regulators (a common part of the alternator) mounted on the outside of the alternator body that can cause variation in amperage usage. The size of an alternator is also likely to increase the overall amperage. High output alternators (often on larger vehicles) can use between 200 to 350 amps. Comparatively smaller cars, such as a Ford Mustang, will only use around 100 amps with batteries running at around 12 volts.
Determine the fuses on your vehicle’s electrical components. You can estimate the amperage of your alternator by running it this way. Look for a diagram under or near your fuse box cover. It will have individual amperage numbers (sometimes along with volts) already stated by the manufacturer. Add the numbers together to find what amperage your alternator needs to power the car’s electrical system. Verify this number with the part manufacturer, if necessary.
Use a formula to calculate the amperage. For example, if you have a component (in this case an alternator) that needs a certain amount of watts (also known as “amp load volts”) to operate, you need to set that as a mathematical variable. Most common equations use the “I” to indicate amperage.
Set the math watts variable to VA (the volts times amps), and then divide the above two variables by the volts or “V.” The equations will look like this: I = VA / V (Amperage = watts / volts). Consult the alternator specification guide or contact the alternator manufacturer if you do not see the wattage number written on the alternator. An example equation for a basic amperage number might look like this: I = 1200/12 (Answer: 100 amps).
Tips
Have a mechanic use an ammeter to test your amps.
Alternators generally have four parts: a rotor, stator, rectifier, and regulator. Alternating current (AC) is made by the stator and the rotor (AC is what happens when mechanical energy changes into electrical energy.) It is sent to the battery voltage that powers the output of the lights.
Fuses are devices that protect electrical circuits.
Warnings
Avoid electrical hazards. Take either your car or alternator to a professional.