0. Briefly, the alternator and the battery
Your car battery's primary task is to hold power in reserve to crank the starter. Its secondary task is to prevent damage to car electronics while the alternator is running (so don't operate a modern car with the battery disconnected!). Starting the car puts a large strain on the battery's power reserves.
The alternator's primary task is to keep the car electrical systems running, by acting as a generator powered by the engine. This includes the headlights, stereo, power steering, fuel injection and ignition. The more power the car needs to run, the harder the alternator must work. Alternators are rated by amperage (our Corolla/Prizms use 80A alternators). Any power not being used to operate the car is used to recharge the battery for the next start.
Obviously, if the alternator is weakening, less power is available. The headlights may dim when the A/C is on; less power is available to recharge the battery. On a short trip, the battery may not even fully recharge. After many short trips, the battery may no longer have enough power to start the car, and you will need a jump start. Eventually the alternator may die, which will leave the car inoperable once the battery is drained.
Keeping this in mind, if you find yourself needing a jump start, consider using an indoors trickle charger, or having a car parts store recharge your battery afterwards. This will extend the life of your battery and your alternator.
1. Diagnosing a failing or dead alternator
It can sometimes be difficult to determine if your alternator, battery or starter are at fault. Roughly, symptoms of a bad
- Car needs jump-start in the morning or after short trips
- Car cranks one time without starting, but cannot be cranked a second time
- Car suddenly loses power while driving
- Turning on one accessory (high beams, A/C, defroster, window motor) causes interior or headlights to dim
- -BUT- the car always starts when jumped
If your car cannot be jump started, the problem is likely to be either bad battery connections or the starter. In the worst case, you might have several things go wrong! In my car, the positive battery terminal was badly corroded. This part is easy to replace, and can be ordered from Toyota, part number 90982-05035 (Terminal).
A multimeter is your best friend when doing diagnostics. Cheap ones can be ordered online or found at Radio Shack. Read reviews to make sure you are getting a good one. Make sure it has a usable DC voltage range (ie, 20V). Start with a known charged battery (use a trickle charger or a store that offers a free quick battery charge), and check the voltage between the terminals. A good battery should read above 12.4V with the engine off.
Start the engine and check the voltage. It should read between 13.5-15.1 volts. Rev the engine, and see if the voltage increases. If the voltage exceeds these limits, the alternator's regulator may be faulty. Try turning on high beams, the A/C and the defroster. If the voltage is low, the alternator is weak. If the voltage is in the proper range, peel back the boot of the alternator wire, and run one of the multimeter probes. If the voltage is very different than between the battery terminals, it may just be a bad wire or terminal.
For example, on my car, the voltage was 13.84V on start, but dropped to 12.35 when all accessories were turned on. Revving the engine only increased voltage to 12.89V, still too low for safe operation, much less to recharge the battery.
2. Alternator alternatives
I'm a cheap guy, and lazy to boot. With most repairs, I'm happy to use whatever part saves me the most time and money, and is of a sufficient quality to not need replacement for a reasonable amount of time or cost. So I normally avoid buying Toyota/AC Delco parts if there is a good alternative available.
You'll find much debate online about the quality of various alternator remanufacturers. Many people recommend finding a local alternator shop to do the job. This may be a good option if you can spare the time without your car for the work to be done. The local shop will usually offer a short warranty to ensure the unit at least works.
Your next choice is to buy a remanufactured unit with a core charge. BBB Industries, Remy, Denso and Bosch all sell remanufactured alternators, under their own names as well as other brands. Advance Auto store brand are Remy units, NAPA and CarQuest use BBB (though this may vary from store to store). Warranties vary, from 1 year on the Denso, 3 on some BBBs, to lifetime on certain Remy and BBB units. That said, the quality can vary immensely, and may not correlate to the length of the warranty. BBB and Remy units remanufactured in Mexico can be of debatable quality, with stories traded online of units failing after weeks or operating fine for many tens of thousands of miles. This may be somewhat mitigated by the good warranties you can find on these units, at least if you are confident in doing the replacement, and live near one of the stores where you can obtain replacements.
Bosch and Denso are more highly regarded, but cost accordingly more. Some Advance Autos (and possibly other stores) have the equipment to test an alternator in the store (this is different from the in-car test). This free service is worth considering if you buy a store-brand unit.
In my case, the Remy unit I bought first failed immediately -- no power. I returned it for a full refund at AAP, and ordered a Denso from their site, which so far (knock on wood) is working perfectly. The Denso was remanufactured in a US facility. It's a shame I found out about the alternator bench testing after I installed, removed and replaced the Remy unit! (on the up side, I can replace my alternator in no time flat) ;-)
Here are the costs for the alternators I looked at:
Toyota reman, from Mid-Atlantic Toyota: $214 + s/h & core (1yr warranty) (possibly a Denso?)
Denso reman, from Advance Auto + discount code: $157 + core (1yr warranty)
Advance Auto ToughOne (Remy) reman, + discount: $90 (lifetime warranty)
AC Delco reman, from RockAuto: $147 + s/h & core (1yr warranty)
NAPA Rayloc (BBB) reman: $125 + core (3yr warranty)
You'll have to determine where the balance between cost, reputation/quality, and warranty meet for your needs.
3. Further reading
Car and deep cycle battery FAQ: http://jgdarden.com/batteryfaq/carfaq.htm
Paul's Corolla guides (9th gen, but very easy to adapt for 8th)
Remy charging system troubleshooting guide:
First, I'd like to thank FishExpo for running Corolland. Forum gurus dshadle1, Dom, (Fish, again), Paul from paulstravelpictures.com (whatever your user name is), and everyone I'm forgetting -- thanks! I've been a reader of the site and forums for a long time now, and have learned an immense amount from the discussions here. This HOWTO is an attempt to in some small way give back to the community for all the help I've gotten. I hope it's useful to someone, and as expected, I am not liable for any damage you or your vehicle suffer for following these crude instructions ;-)