ELECTRICAL SYSTEM, BACK-TO-BASICS: THE ALTERNATOR

[Stewart G Griffin]

I am ASSuming that all GM vehicles from, say, 75 to 87ish used the exact, same alternator exterior shape wise?  Because they all look identical.  I understand that some alternators put out more juice, but the body was/is the same and thus should be interchangeable to the point where they will bolt in?

Mine has the 3-wire hookup.

83 c-10
350

[VileZambonie]

No they are not. The end frames are different and yes they are different amperage ratings and pulley ratio's. BTW why do you always start your posts with the basics?

[Stewart G Griffin]

1) i start with the basics because i believe that we should have a firm grounding in the basics;  Not enough emphasis on them---too much on show and go, chrome etc.

For instance, how many people really know(or care about) the electrical system and how to install gauges properly etc.  Or the brake system? 

The engine is sexy, but the other stuff is important too.

2) Since all the alternators are differnet, Could you then please assist me on identifying the right alternator for my application?

[VileZambonie]

Your best bet in finding direct fit parts for your application is by looking up your year truck with the engine application and wiring harness application you have.

Everyone here seems to care about the questions in which they post topics on whether it be their gauges, brakes, charging system whatever, so you don't need to put  "The basics" in every single one of your posts. Believe it or not it makes all of your posts look the same and people may over look them.

You have an SI alternator from the factory. It has an internal voltage regulator and you can get one brand new cheap from Autozone and the like. $34.99 http://www.autozone.com/R,APP194386/vehicleId,1193410/initialAction,partProductDetail/store,5152/partType,00086/shopping/partProductDetail.htm

[Stewart G Griffin]

i think i'm going to go with the Bosch reman unit from Advance.  It runs for $124, $22 core.

My philosophy is since i saved about 30 thousand  by not buying a new silverado, i can, should, and must buy top of the line, better than stock parts.  And still save money by not buying a new truck.

[dumbucket1]

I used to have the same mentality of not buying a new truck. Then I bought an 07 Sierra and boy is it nice to be able to get into that truck and not think twice about going anywhere at any time, unlike my old trucks which although they would most likely do fine I am not willing to find out the hard way if they will make it or not.

And ya writing the basics is annoying it kind of sounds like you think we are all in the 3rd grade or something.

[rdhack]

Oh heck.......Never buy electrical parts from Advance. You'll discover that you will be using their warranty, but I hate all the extra LABOR which is not covered.

[Stewart G Griffin]

It turns out the alternator was not the problem.

Are (and i will explain my reasons for asking such seemingly simple questions in a sec) alternators "engaged" all the time?  In other words, do alternators put out power all the time and at all/any rpm's?  If so, are they harder to turn when they are putting out power vs. not putting out power?

The reason i'm asking is because i have a very bad squealing problem that only lasts for about 1-2 minutes after startup.  So, i'm thinking that since it took quite a bit of energy from the battery to start the engine, the alternator, immediately after the engine fires up, is working extra hard to put back energy into the battery but this means it is harder to turn and the belt is slipping,  thus causing the belt to squeal bad.  After the battery is charged up the alternator does not need to put out that much energy making it easier to turn and the belt does not slip anymore so the sound stops?

[choptop]

Alternators on these trucks are not always on. They receive voltage from the ignition switch to excite the alternator and the regulator then controls the charging. When the engine is turned off, the alternator stops, and since the regulator is not seeing the voltage produced by the alternator, it turns off. If the alternator is draining the battery, then it is usually a bad regulator, that is not easily replaced.Once the batteries are charged, the power draw on the engine is reduced, but it still maintains the desired voltage. A 60 amp alternator does not always put out 60 amps. It may after it is first started to recharge what was used, but when  the voltage is back up, the amp output goes down. Load on the alternator with a charged battery depends on the trucks accessories(stereo,a/c, etc.) As for the load on startup for the alternator, it does not produce any output, until it reaches a certain rpm (alternator not engine). This is what I believe Vilezambonie was referring to. If you have the wrong pulley ratio, the alternator will not spin fast enough to reach the proper engine speed. I encountered this when I put a 84 diesel alternator, and my 81 350. It took three different sized pulleys before I found the right ratio. If you put a different model alternator on, be prepared for some custom fabwork to get the belt lined up right

[Stewart G Griffin]

Ok, thanks for the background on alternators.

It turns out that it very probably is the belt because i just unpluged the three wires to the alternator and started it up---no fuss, no muss, and absolutely no noise.  i also noticed that the belt was a little loose;  This is the stock alternator bracket and apparently these are a little tricky to get the belt tight?  Someone suggested that i use a large screwdriver sort of as a pry bar to get some tension on the belt.

[choptop]

sounds like you got it. Alot of these have a large whole in the top alternator bracket,that the factory tire tool slips in perfectly, and allows you to put tension on the belt without straining. Just be careful, I munch the bearings in one years ago because I got over zealous

[autorepr]

Try to get the tip of the pry bar (what ever it may be) against the drive end/end of the alt that's closest to the belt. If you jam the tip against the middle you can actually distort the housing and the rotor will grind the stator and you'll be replacing it again. When prying it back try to turn the fan of the alt. by hand. Stop prying at the point you start actually turning the crank pulley by turning the alt. pulley. Hold that amount of pressure on the pry bar and tighten the mounting bolts. That will insure correct tension every time without ever over tightening. Some times you can slip a pair of slip joint pliers in and "pinch" the slide ear and the bracket together in the direction it slides instead of a pry bar but its a little tougher to do.

You can check for a loose belt the same way less the pry bar. If You can turn the alt pulley without turning the crank pulley, it's to loose. MAKE SURE THE ENGINE IS OFF AND THE ONLY IGNITION KEY IS IN YOUR POCKET so no one can hop in and crank it.  A couple dopers in high school autoshop were screwing around and one had his finger on the alt belt wiggling it up and down as if that was going to tell him anything and his good buddy cranked the engine over. Oh they got his tip back on but it was squirting blood for a while!!! (His girlfriend wasn't to happy)

Just one more thing, clean ALL the mounting points so you get a good ground path. Alt to bracket, Bracket to cable, cable to battery. 

[werewolfx13]

I ALWAYS check for belt tension by moving the belt up and down. 1" of travel = perfect, more = too loose, less = too tight and you'll more than likely trash the bearings in the alt or water pump.