Alternators fail for a variety of reasons. Sometimes, it's just normal wear to the windings and diodes that eventually causes total failure. Sometimes, the bearings inside the alternator can wear out. But whatever the cause of failure, alternator replacement isn't optional.
The question is, what kind of alternator should you buy? OEM alternators can often cost considerably more than after-market alternators, and for that reason many people opt for a cheap after-market alternator instead of an OEM replacement. If you're wondering why cheap alternators are a bad idea - and why you should always buy OEM alternators (new or remanufactured) - read on.
The Trouble With Cheap Alternators
After-market alternators are sold as OEM replacements, but most after-market replacements are not at all identical to OEM units. From manufacturer to manufacturer, the quality of an after-market alternator will vary greatly. The problem is that consumers often can't spot the differences in quality without learning a little bit about how alternators work and why cheap alternators are bad.
Here's what you need to know about cheap alternators
1. Output wattage isn't always up to spec. One of the easiest ways to reduce the cost of an alternator is to reduce the maximum output wattage the alternator can produce. Thus, many after-market alternators don't offer the same maximum wattage as the OEM unit they're replacing. This means they could generate insufficient power in situations where the vehicle is using a lot of electrical power (say, for example, you've got all the electronics and lights on and you're doing something demanding like towing).
While it's true that you often won't notice the effect of an undersized alternator, an underpowered alternator can cause your battery to discharge completely. THAT's a problem you'll notice, at least when you try to start your vehicle after the fact.
2. They often waste fuel. A cheap after-market alternator can cost you a lot of money at the gas pump. Believe it or not, most OEM alternators are designed to be super energy efficient. This helps improve the vehicle's fuel economy, as a more efficient alternator uses less of the engine's drive power to charge your battery and run your electrical system. OEMs are very concerned about fuel economy, as fuel economy ratings are closely regulated (and automakers must pay a penalty if their vehicles don't meet fuel economy standards). Therefore, OEM alternators are very energy efficient.
But if you replace a top quality OEM alternator containing a high efficiency diode with a basic after-market alternator containing cheap diodes, you'll waste money. You'll probably "save" $50 on the cost of the alternator, but you'll see fuel economy fall 1-2%. That doesn't sound like much, but it adds up to $20-40 per year, depending on the type of vehicle you drive (bigger vehicles save more money with efficient OEM alternators). After a year or two, you're losing money.
3. They're usually louder than OEM alternators. Another area where after-market alternator manufacturers can save is on the roller bearing that provides drive to the unit. OEM alternators use expensive bearings to limit both noise and increase efficiency, but after-market alternators often cut a corner on the bearing to save money. It's a small thing, but it means your engine is a little louder than it was before. It also means your after-market alternator bearing isn't going to last as long as a quality OEM unit.
If you've heard the expression "buy nice or buy twice," you know the problem with cheap bearings. They save money today, but you'll have to buy another one sooner than you'd like.
What You May Not Know About OEM Alternators
Besides covering what after-market alternators lack, OEM alternators are unbeatable in a serious way: They're far more protected from vibration damage than the average after-market alternator.
OEM alternators are designed to resist damage from vibration. They have features like:
- Chassis suspension systems, which isolate the alternator from sudden jolts that can damage bearings
- Gel-packed electrical connectors, which both protect connectors from the elements and keep them from literally shaking apart
- Smart bracket designs that limit movement in certain directions
These features are important because - in news that will come as a surprise to no one - cars hit bumps and potholes daily. What most people don't realize, however, is that these bumps and potholes (and the vibrations they cause) can lead to damage to every component of your vehicle, including your alternator. Few after-market alternators are as protected from vibrations as OEM units. While this vibration protection isn't something you'll notice right away, it might be the difference between buying (and installing) yet another after-market alternator in 2 years or never buying another alternator again.
While some after-market parts are worth buying, beware the cheap stuff. Cheap parts are not made to the proper specs, they're not made to be as efficient or durable as OEM parts, and they're not as well designed. When it comes to buying a replacement part - especially a replacement alternator - OEM is the only way to go.