Hey Gus....

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#1
This is my wife's van...98 Pontiac Trans sport...3.4...VIN E.....it has the Valeo 105 amp alternator...Van was doing fine...The other day went to start it and the battery was dead...so I jumped it and it started ..then I checked the alternator...it was not charging...the thing has an idiot light, no gauge..the light never came on..OK..so the alternator is a real PIA to change...I got a re man unit put it in and drove it for 1 day..same thing dead battery...checked the alternator..not charging so I got a different unit from a different vendor....Just got it in tonight and put the tester on it and it shows it is not charging...I checked all the fuses and took the battery cables off and cleaned them and put a new battery in it..I am lost as to why it is not charging...Am I missing something?....other than my mind..LOL.....thanks for any help you can give me....Jim

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#2
OK...I turn the key on the idiot light comes on, start the van and the light goes out...unplugged the connector on the alternator, turn the key on, the light comes on, start it the light goes out...doesn't make any difference either way...Jim
 

Gus

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#3
Jim, you are correct about pulling and installing an alternator in a U-van.......

Looking at the schematic, I'm sure you used a test light at BAT terminal(where the nut is on the back of the alternator).....this confirms the fuseable link isn't open......also at the S(D) terminal, to check the alternator sense fuse........


all the PCM does, is control the idot light....only turns it on if voltage is too high, too low, or if the engine is not running.....the alternator regulates itself......more often thean not the fuseable link is blown.....
 
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#4
OK...here is the latest...I put the test light on the battery terminal..(thought I did that before) anyway ..it didn't have battery power...showed ground...so I tried tracing it back along the wiring harness..it came down along the radiator towards the PCM..I was trying to find the fusible link...so I pulled the cover off the PCM and was checking the wires in the harness (they go down by the starter area) I see some fusible links and I checked them with the test light and they had power,so I went back to the Battery terminal on the alternator and (yep..now it has power)....put it back together and checked and now the alternator is charging...so...did I wiggle something and make it work and later it will quit again?....Jim
 

Gus

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#5
Absolutely......if you had no power at that nut(should be hot at all times), and then you moved a harness and now have power, there is a bad connection somewhere....I would start at fuseable link "A", at the starter....
 
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#6
"S" is the sense terminal, really doesn't need to be connected as the voltage regulator will automatically switch over to local sensing at the BAT terminal. But due to voltage drops across that rather thin BAT cable, remote sensing with the "S" terminal is preferred. If not connected, Bat voltage will be lower, but as the battery charges and loads decrease, will be pretty close to the regulator preset voltage of 14.5 volts at 25*C.

That leaves the "L" terminal on the VR connector to worry about it, gets, 12 volts from the ignition switch via the PCM, PCM is in there to switch off the alternator under heavy engine loads. With KOEO, should measure about 2 volts at the L terminal, an internal transistor is on ignited the lamp, but it only takes 1.2 volts to turn on the VR inside the alternator. In earlier vehicles, L terminal was connected directly to the ignition switch, didn't fool with the PCM. If the field circuit is good and voltage is induced in the stator windings, well, we called that the P terminal for phase as S is being used for sense. That P terminal switches off that lamp transistor killing the lamp so the L terminal will go back to the battery voltage.

Ground is obtained through the frame of the alternator that unfortunately uses a grade of aluminum for conductivity that corrodes, hey that good grade of aluminum costs a few cents more, can't do that with the stockholders, so you have to wire brush those connection points and silicone grease helps to retard corrosion. We could have added a separate ground strap, but more money out of the stockholders pocket. But that doesn't stop you from adding your own ground strap, I added mine.

BAT terminal also didn't have a fusible link originally, was added later as if the positive and negative diodes both shorted out, would put a direct short across the battery that could cause an underhood fire, stockholders bought that. Also would prefer to run the alternator battery terminal directly to the battery the way it should be, but slightly cheaper to use the starter solenoid terminal as the junction point where it can corrode being exposed to all that road salt. More than likely, that is where your problem is at, remove the negative battery cable, wire brush the terminals, use silicone grease, and it should last awhile.

I prefer using a voltmeter between the frame ground to the neg bat terminals and between the alt bat terminal to the positive batter terminal to check for voltage drops. Ground should be under 0.1 V, but the battery side can be as high as a volt due to the small gauge wire used and depending on load, but that is what the S terminal is for.
 
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#8
When I rewired my P-30 motorhome chassis, alternator wire was ran down to the starter solenoid Bat terminal, then way back to the body connector. Put in a new wire directly from the alternator to the body connector and had ten feet of old cracked wire left over. And only have two wires running down to the starter motor, 14 AWG for the solenoid, 6 AWG for the motor, a lot simpler and far more reliable.
 

Gus

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#10
Yeah, where those fuseable links come together on the starter, they either loosen or corrode....knew you'd find it....
 
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#11
Still a dumb place for such an important connection, an erratic connections induces high voltage transients, least that alternator has suppression diodes, but still get 27 volt spikes that can damage your electronics. Hopefully, your replacement alternator has those OE type of diodes, many rebuilts use conventional diodes to save a half a cent, those have led to disasters.

Don't mean to sound negative, I worked in this field and have seen all kinds of failures, like on an average of 3 million per year. Function of the battery is to start your vehicle, and to act as a filter for the alternator, very much part of the alternator system, every time the field is switched on or off, in this case 400 times per second, a transient is developed, battery filters that out. But can't do that unless it's securely connected to the alternator.
 
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#13
Not my favorite vendor for rebuilt products, better choice would be the NAPA premium line, same rebuilder is used to rebuild Delco products. You should hear the manager of my Carquest store cuss out the rebuilders the home office selects. I even tested a few. You could have gotten a good OE that just needed brushes, or a bunch of old sandlbasted parts. Sand blasting the inside of the rear cover where the main rectifiers depend upon could thermal conductivity is a no-no.
 

Gus

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#14
We have to use aftermarket parts to stay competitive.......unfortunately, cars return with the same problem.......may take a day or to, even a couple of months.....

Try to explain to the customer, if we put a GM part in, diagnosis, part, and labor are covered on a comeback.....with an aftermarket part, the part gets replaced by the store, but diagnosis and labor is theirs......they usually go with the aftermarket part, because it's cheaper than the OEM.....but ends up being costlier when it comes back with a part failure....

Starters, hub/bearings, alternators.......fuel pressure regulators......sensors, especially rebuilt MAF sensors.......could go on and on....
 
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#15
Not saying all stuff from Carquest is bad, actually got a brand new Honda master cylinder from Carquest for 40 bucks. Their main distribution center for all of central and northern Wisconsin is in my home town, so can get anything they list in their catalogs, instantly.

A dead give away on alternators and starters is if they way coarsely sand blasted, not the way to rebuild an alternator. Another nasty thing they do is to ream out the center of the stator to increase the gap because their rotors do not run true. This drastically increases the eddy current in the stator laminations, and to ream it, have to bend the stator wires outward that puts cracks in the stator windings.

Only advice I can give is you have to know what you are buying, if I see a water pump that came with a stainless steel impeller that was changed to a cast iron job, I say no thanks.