Auto and Truck Repair and Advice
Serving the Gainesville and Hawthorne Florida Area

Alternators and Generators

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ALTERNATOR REPLACEMENT: $100 TO $300 (Parts and labor)
(Prices good for most cars and light trucks)


The alternator or generator keeps your battery charged. It also provides power to run your lights and other electric accessories on your car while it is running.

IMPORTANT NOTE:

If your car starts and runs, or if the engine turns over normally when you try to start it but it won't actually run, there is probably nothing wrong with your alternator, starter, or battery. The only exception is if the alternator is OVERCHARGING: in other words putting out too much voltage. This can "DRIVE THE COMPUTER CRAZY" while the engine is running, and cause all sorts of weird problems.!
You could completely remove the alternator from the car and your engine would still start and run normally UNTIL THE BATTERY WENT DEAD!

An alternator is an A/C generator. Cars used to have generators, since cars run off DC current. The reason manufacturers went to alternators is that they charge better at low RPM's. The A/C output of the alternator is changed to DC by rectifier diodes in the alternator, so a car alternator really puts out DC power.

Symptoms of a bad alternator include hard cranking, lights that seem too dim, and of course the "BATT" or "GEN" light glowing on the dash.

TESTING
Put a voltmeter across the battery while the engine is running . Voltage should be 14.2 volts. Lower than 14 volts or higher than 14.4 volts could mean a problem. Turn on the lights and accessories: voltage should stay up around 13 volts. Idle engine up to 2000 RPM. Voltage should go up to 14 or so.

SPECIAL NOTE FOR NEWER VEHICLES

The newest alternators are "temperature compensated". This means they charge at different voltages depending on the temperature. A hot battery requires less voltage to charge than a cold battery, so the temperature compensated alternators charge at a lower voltage when hot than when cold. In any case, any voltage reading below 13.5 volts or so is a sure sign of trouble.

SPECIAL NOTE FOR OLDER VEHICLES: VOLTAGE REGULATORS:

All alternators have a voltage regulator circuit which keeps the voltage at the ideal 13.8 to 14.2 volts needed to run the car and charge the battery. Most newer vehicles have a voltage regulator which is part of the alternator, but older vehicles have the regulator as a separate part. Some Chrysler products used the vehicle computer to operate the alternator: the voltage regulator was inside the computer. On most other vehicles the regulator was mounted on the inner fender or the firewall. Testing is different for different vehicles and I can't go into all the different tests here, but any good repair manual will have test procedures for making sure the regulator is OK. So if you have a vehicle with a charging problem, and it has an external regulator, make sure to test the regulator before you replace the alternator! NOTE: BAD ALTERNATOR SYMPTOMS ARE VERY CLOSE TO BAD BATTERY SYMPTOMS AND BAD STARTER SYMPTOMS A properly operating alternator cannot charge a bad battery!

Your car can run for a short time with a bad alternator. How long depends on how much electicity your car uses. A car with a mechanical fuel pump can go pretty far. An electronically fuel injected car with electric pump can't go very long at all. No car can make it far at night with the lights on. So if the "BATT, ALT,or GEN" light comes on, no need to immediately pull off the road, but get things checked A.S.A.P.! Also watch your temperature gage! You may have broken a belt, and this could cause your engine to overheat. Should the car overheat, you should stop as soon as safely possible. Either check it out yourself or get it to a mechanic. Special note to air cooled V.W. Beetle owners and Corvairs (Yes, there are still some around!!): the alternator or generator belt turns your cooling fan, so if the light comes on, check the belt very soon: it can severely overheat in a very few minutes!

Buy a Replacement Alternator from PartsGeek.com- Click Here


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We also serve the surrounding communities of Alachua, High Springs, Hawthorne, and Newberry!

Thank you for visiting the ECONOMECHANIX WEB SITE. Please feel free to comment. We also serve the surrounding communities of Alachua, High Springs, Hawthorne, and Newberry! Gainesville has been my home since 1974, and I've loved Gvl and the Gators since I came here in the fall of 1974 to attend the University of Florida. I loved it so much I stayed and opened my car repair business. Originally it was out of the back of a 1963 Chevrolet wagon, but in 1977 a fellow mechanic and I opened an auto repair shop with actual walls, etc. I stayed in the same location for 26 years, and recently moved my operation to property I bought 15 miles east of Gainesville. I am doing most all the repairs myself now, having reduced my overhead from $1500 per month to practically nothing. I do work by appointment only. I mostly work only on my established customers cars, but I will occasionally take on new clients. E-mail me and I will either make arrangements to look at your car, or I will recommend you to someone who will.

George G. Scott, Jr.