OK - I know I can just take the alternator to a part store and have them check it out for free. But, reading through the schematics of the charging system in the Helm book, shows a very simple system. I figured I can simulate that by having a good 12v battery, run a 10g wire from the "bat" post of the alternator to the pos(+) side of the battery, another 12g wire running from #2 0r "A" of the two prong connector to the pos(+)10g wire, run a 10g wire from the neg(-) post of the bat to the alternator body for ground and hook up a voltmeter to the bat posts to see if the alternator is good. I tested a known good one and a known bad one. The bad one was in the car and when the light in the dash came on, I checked the voltage at the bat and it did not change when reving the engine a bit. So I did the "full load test" by grounding the regulator from the "D" hole of the alternator and the voltage increased to 16v immediately. So I removed the ground (not good to overcharge the Bat), which tells me the alternator needs rebuilding. But, when I hooked the good alternator to the "home made" setup, nothing changed. I think I was spinning the alternator over 1,000 rpm.
1-Is it possible the rpm's are too low?
2-Is my setup wrong?
So, who can expand on this? Now remember I'm only checking SI versions for now. I have four alternators to check. I would also like to check them for amps too if that's possible.

the spec sheet with my alternator showed a 1500 rpm turn on rpm.

you will need a load tester to create a load on the alternator, basically a big heavy guage wire resistor. you will also need about a 2+ hp motor to drive it at full load. alot of investment. you're not gonna run that with your drill!

building a load part won;t be easy either, and they are not cheap to buy. you could make up a 10-20 amp load from paralleling a bunch of 50w driving lights, about 4 amp apiece at 12v, but to pull 80 amps out of it you wil need either a carbon pile or a resistor coil form a battery tester. also a 100 amp guage.

alos the lamp line is used on some of these to turn them on, so hook a bulb up to that to 12v. alot of work, but I guess it would be cheaper than 4 40$ reman alternators.

The best way to check an alterantor is running in the car. Does the battery voltage read about 14-14.5 volts after starting? Much lower than this and the alternator is weak or shot. Also you can see if the alternator is puuting out by placing a steel screwdriver in back of where the the rear bearing/center shaft is. If the screwdriver is pulled with a magnetic force then the alternator is working. No magnetic force then it's not.

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87GT 3.4 Turbo- 0-60 5.2 seconds -Best
Engine Controls, ECM goodies, Chip
re-programming & odd electronics stuff

It should be noted that a CS type alternator will not turn on if the battery is completely flat. I want to say that it needs to "see" at least 12 volts on the battery.
This is to prevent a heavy current load on the alternator, and a possible burnout.

Here's a link to the CS page on Ogre's Cave
http://home.comcast.net/~fierocave/cs130.htm

TheOgre's home page.
http://home.comcast.net/~fierocave/

tjm4fun - u say 1500 !!, come to think of it, the crank pulley is about 6" and the alt pulley is less than 3" on the V6. That means if the engine is at about 1000 rpm, then the alt is turning around 2000 or more. I also notice that the engine showed a slow down when the alt was good and it kicked in. It used to squeel the belt for a split second. So you may be right about a load. I was going to use an old 1/2 hp elec motor from an old appliance to drive the alt. Still, I need to keep trying. Just need to know if someone can verify if my wiring makes any sense.

Dennis - I did check the alt with the "screw driver in the back" method and found the alt needs rebuilding.

Raydar - Appreciate the links, but as I wrote I'm using SI alt pre-88. I don't believe Ogre's cave mentions home made tester, off course I might have missed the section too.

quote Originally posted by rubyredfiero: Raydar - Appreciate the links, but as I wrote I'm using SI alt pre-88. I don't believe Ogre's cave mentions home made tester, off course I might have missed the section too.

Oooops. My bad.
I'm working nights, this weekend. Haven't been awake for too long. Sorry.

appliance motors either run at 1875 or 3750 rpm, unless it's a real oddball so a 1:1 should work for the pulley. you will likely be able to pull about 20 -30 amps out of it for a test at best before you stall the motor.

how you are going to load it, well that's your problem!

tjm4fun - don't know what method to use for loading it. Is it necessary to be loaded? This is where my ignorance shows it's head, so pardon my lack of electrical knowledge. Any suggestions? Other than buying a carbon pile.

Dennis...not entirely true on the output test with the alternator in the car.

I used to think the same thing...I tested my alternator in the car and was getting a reading around 13 or below. Of course I figured it was the alternator....turned out it was a bad battery. Evidently there can be charging issues that will give false readings if the battery is bad....something to keep in the back of our heads I guess. Who knew!?!? I didnt...

Powr

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quote Originally posted by rubyredfiero: tjm4fun - don't know what method to use for loading it. Is it necessary to be loaded? This is where my ignorance shows it's head, so pardon my lack of electrical knowledge. Any suggestions? Other than buying a carbon pile.

yes you do need to load it to really test it. you will need to have a good battery on it too, as these alternators are not designed to run wthout a battery. they will work if you start them up and disconnect the battery, but it drives the regulator too hard and will usually fry the regulator.

for a load, that;s gonna be rough, you really need to try and pull at least 20 amps out of the unit to get an idea if it is working. put your amp guage on the + lead to the battery, and connect the load at the battery end, so the system is in a normal setup.
as I said, driving lights ar about 5 amps for a 55w unit, headlights are about 8 amps with both high and low lit. just trying to think of junkbox parts that will make a decent load..... I really have no idea what an unloaded starter motor will draw, but I would suspect free running around 15 amps, but you can;t run a starter for long periods or you will burn it out, as they have no cooling and are not meant to run for long.
you could probably get 6 dual beam headlights from a junky fairly cheap , figure one beam will likely be blown on a couple.

now the trick is to watch the voltage at current draw. with just the battery, it should be about 14.4 v. with a load on, you xhould be able to hold 13.5 volts, as long as your electric motor can take the load and the keep the rpm's up.

Need a load, huh? Hmm, when I'm testing laser power supplies I've been known to use old heating elements from furnaces, dryers, water heaters, etc. for dummy loads and/or current limiters. Watts = Volts X Amps.