THE BASICS: ALTERNATORS

[Stewart G Griffin]

So anyways, it looks like i need a new alternator.

I have pretty much a stock setup and am not interested in going fast.  I'm more interested in reliability and durability.  I am, however, not against buying top quality parts(even if this means "high performance").  I feel i can do this because i don't have a monthly payment, or interst payments, or high insurance;  The money saved here can be applied to top of the line parts and still have $$$ left over.

With that in mind:

1) We have 140 amp even 160 amp alternators.  Do these last as long as "stock" alternators?  An analogy would be a higher compression engine generally does not last as long to overhaul than a lower compression engine.  The higher compression engine offers more performance and better MPG, but they generally don't last as long as a lower compression engine.  Are alternators the same way, or is bigger always better with alternators?  Should i just stick with the stock 60 or 70amp units?

2) What's the best alternator money no object?


3) Is it possible to "hurt" the electrical system or battery if you use a 140 amp alternator without beefing up the rest of the electrical system?

[SUX2BU99]

10-15 years ago, an alternator over 100 amps was rare, very expensive ($600+) and only from the aftermarket. Nowadays, factory alt's can be 140+ amps. My 99 Dakota R/T came with a 136amp and my 05 Magnum R/T has a factory 160 amp! So knowing that these sizes from factory this large, I wouldn't worry too much about reliability. I'd worry about a tiny 60 or 70 amp having to work hard putting out most of its current capacity to perform your trucks functions. An alt will only supply the amount of current demanded from it, so replacing a 70 with a 140 won't hurt anything. The only thing to watch for is the 'hot' rating and at what RPM you get full amperage at. Most alternators do not provide full current capability at idle speeds, but that's okay unless you like to have your a/c, wipers, stereo, high beams and heater fan on at full blast. It's still better to have a high-amp unit though because they will still provide more current at idle than a smaller one.  I believe the only thing that makes a larger alt any more different than a smaller one as far as operating goes is the mass of the parts inside, like the windings, stator, etc. But this is minor. Heat kills alternators. GM small-case units are famous for burning out and I think that's because they are 105 amp units in small cases with heavy loads on them that don't adequately vent themselves.

A brand out there that I know is good is Powermaster. There are some other smaller brands out there that cater to the high-wattage car stereo crowd but Powermaster is one of the biggest names that I can think of. Wagner used to be a big name back in the day. Another source of high-amp units are ambulances.

Another very good idea to improve your electrical current flow is upgrade the 'big 3' as they call it in the car audio world. This would be your battery positive to alt cable, battery ground to frame cable, and engine ground to frame cable. Replacing the terminals with new and going with at least a 4 ga. cable can improve your alternators performance. I did this on my truck and saw at least 1/2 a volt gain on the factory ammeter.

[Captkaos]

Unless you are running a electric winch, offroad lights, rock lights, booming stereo and you A/C ALL at idle, you can get a GM CS-144 alternator and put in on your truck.  They were introduced in 1986 and put out about 100 amps at idle (rated at 140amp).  They are generally around $200.  They have them now modded to put out up to 200-250 amp max.  You probably want to upgrade the charge wire on the older trucks to about 8 gauge.

Here is a good explination of Alternators:
http://www.1stconnect.com/anozira/SiteTops/energy/Alternator/alternator.htm

[VileZambonie]

I just did the CS SI conversion when I put serpentine belt system in my truck last month. Works mint

[79ChevyK20Guy]

I modded my truck to have a 200amp Nippendenso alternator for a John Deere tractor to power all of my lights for the fire department. Wasn't too complicated if you are good with a welder.