| quote | Originally posted by Threedog:
Is it possible I ruined the internals of the other alternator(s)? With the new one, when it was unplugged it read at 11.9-12v, and when I shut it down and plugged it in it went to the correct high 13/14. With any of the other alternators, it was 12v plugged in and either 10v or sometimes still 12v when uplugged.
Edit: Just tried the older alternator to see if it works, won't hit above 12.1 under the exact same circumstances as the new one. I must have screwed up something on the inside.
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Even though the problem has been solved, I thought I would respond to make this thread more useful for future use.
Here is some interesting reading on CS130D alternators. Given the year, your alternator may be a CS-130D. The output of this alternator is not PCM controlled but as seen below it can be wired to the PCM for other reasons.
Found this at http://oljeep.com/gw/alt/ed...ternator_Theory.html
(and yes, the Cavalier does use the CS130D alternator)
P-Terminal: Provides a 12Vdc square wave as in the CS-130 application. [The Pulse/Phase terminal can provide a 12V square wave to determine alternator speed, used by some Electronic Control Modules or vehicle computers. Connects to the stator. Some ICU’s monitor this signal and adjust engine parameters accordingly.]
F/I-Terminal: It gets a bit tricky here, as some applications do not incorporate a lamp circuit. In vehicle applications of the “no lamp” kind, this terminal is connected to the Ignition Switch, and an internal resistor is used to limit current and voltage. Other regulators use this terminal as an output and refer to this pin as a Field Terminal, as such, it provides an output that is proportional to the field duty cycle of the alternator to an a vehicles ECM. The ECM now has an input to sense alternator loading and engine loading, and can increase/decrease engine speed accordingly. Here is an important consideration, since the regulators on CS-130D type alternators have these two different types of regulators (F-Type or I-Type) they cannot be interchanged. I-Type regulators use the F/I-Terminal as an input and this can simply be an ignition source 12Vdc voltage that the alternator uses; F-Type regulators use the F/I-Terminal as an output (this ion is a signal that is provided to the vehicle computer and the computer uses it to monitor the field intensity of the alternator as an input. If you supply a 12Vdc signal to this input, you may very well ruin the alternators regulator.
L-Terminal: This is the lamp terminal and operates in the same manner as the CS-130 lamp circuit above. It is of interest to note that some applications use the ECM to send the L-Terminal a signal (5Vdc reference), and the F-Terminal responds with a signal sent to the ECM, in this application the ECM and the Regulator form a “closed loop” to control engine loading and alternator output.
S-Terminal: This is the “Sense” terminal and is connected to the battery. It senses the voltage level of the battery and feeds the regulator circuit this reference so that the regulator can adjust the Pulse Width Modulation to control the alternators output. The S-terminal on the CS-130D regulator is the same size as the other three terminals, unlike that of the CS-130.
The way your alternator is wired up seems to match the set-up where the "L" terminal is getting power from the PCM to activate the internal voltage regulator. The "F" terminal is sending a feedback to the PCM telling it the alternator field duty cycle so that the engine can anticipate load from the alternator. This leads to the possibility that the alternators you got from the autoparts store were really the "I" type alternators and the one from Rockauto was the "F" type The "I" type need to see power at the I terminal (same location as F) to activate the voltage regulator. So the I type won't turn on with your wring harness.
If I read the sequence of events correctly, the original alternator that failed in service showed 10V unplugged and 12V plugged in. With it plugged in it would seem like it is just seeing the battery voltage. If the output of the alternator is still connected to the battery (and the battery is 12V) the only way that you can see 10V at the alternator is if the alternator is placing a big load on the battery. Visualize the alternator trying to function as a motor. Perhaps this a symptom of damage to the diode bridge in the alternator. Diode failure could have been the reason this alternator quit in the first place. Did you see this same 10V behaviour with the replacement alternators from the autoparts store?
It is curious that your battery charger did not charge an AGM battery on conventional mode. AGM batteries are still lead acid batteries. However, they do not like to be charged too fast or overcharged. This is the purpose of the AGM mode on the charger. An alternator is indifferent to an AGM or conventional battery. Nevertheless, my digitally controlled charger (no AGM mode) will not charge a battery if it has been discharged too much. Have to put it on an old school charger for a bit and then switch over to 2A charge on digitally controlled charger. Maybe the same is true of conventional mode on your charger.
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formerly known as sanderson
1984 Quad 4
1886 SE 2.8L
1988 4.9L Cadillac
1988 3800 Supercharged
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