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Charging woes

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1999 9-3 2.0L

My dad's car quit charging the other day. Today I removed the alternator and had it bench tested at local parts store. Passed all tests. Reinstalled it, still nothing. Wiring is complete from Alt to battery. Ground has continuity to battery from alt case. Running off the battery, I unhooked the pos cable at battery and it immediately died so definitely not charging.

Educate me on the idiot light wire on the alternator. It is on when running (cause it not charging obviously). Isn't this an exciter wire of sorts? Seems if it wasn't functioning correctly (blown bulb, broken wire, etc) then the light wouldn't be on at all....

I'm a fair mechanic. Just not much experience with saabs.
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03 vert se-sports pkg, 01 viggen vert
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If there's no voltage coming off the alternator then somebody's tester ain't working right would be my guess. if you pull the battery cable off while it's running and it dies its not charging the battery
 

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That's what I told him and he said there was no voltage with a multimeter he also said it passed the diode test but there is a specific test for that with a multimeter that's what happened to mine it would still charge but when it's set it had a 2.1 amp back drain overnight killing the battery
 

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Discussion Starter · #13 ·
I suspect the shop test also. Gonna try a jumper wire to the exciter terminal and see if that kicks it on. We tried revving it up and still read no voltage. Dad and got a new alternator tonight so if the jumper to the exciter doesn't do it then it's getting installed. Voltage at alternator matched battery voltage so cable is good and not corroded or broken. Ground has continuity to case of alternator. I don't know what else it could be. I'll post back with results.

Thanx everybody
 

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My alternator on my 1998 NG900 just bit the dust last week. Fortunately, I was in the garage and getting ready to leave when it died. Didn't do any bench tests off the car, but definitely quit charging completely. I am in the process of waiting for a replacement to arrive. From my understanding, this is how the exciter wire works: Ignition on sends current through the exciter wire and bulb circuit to the alternator terminal. The current at that terminal is what "excites" the alternator and starts it charging once it is spinning. Until the alternator is spinning and generating current, the terminal acts as a ground, thus illuminating the battery light because you have positive going through on one side and ground coming from the alternator side. Once the alternator is spinning and generating current, it is no longer a ground and the battery light goes out. That is why when you shut the car off but still have the key on, the battery light comes back on. So if your battery light is on, then your exciter wire is providing current as far as the alternator. That is why if that bulb fails, it kills the alternator because the exciter current can't get to the alternator. If any of this is incorrect, please feel free to elaborate. Hope that helps!
 

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So im having a similar issue currently... My car is slow to start so i checked the battery voltage.. 11.6v. Before that i checked to see if the car would start without the belt on and it did. However the battery light didnt come on even with the belt not spinning the alternator.

What steps should i take next? Im going to remove and clean all the connections first.
 

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So i just charged the battery back up to 12.6 volts. Started the car and instantly dropped to 12.02 v. So alternator isnt charging the battery. I then checked the output directly from the alternator with the car running and its putting out 12v flat.

Its just curious that my dummy light didn't illuminate on the dash?? Even when turning the key with the car not running it doesn't come on the dash like it normally does. I removed the green wire and inspected it and cleaned it. Didn't check it for continuity because i only have a basic multimeter ATM that can just check voltage/resistance.

I just replaced this alternator a few months ago with a rebuilt Bosch unit but it really seems like this one **** the bed already right? Simple as i checked it at the alternator directly and only at 12v.
 

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If the bulb is out on your battery light, the alternator WILL NOT charge at all. The battery light should come on with the key on and the exciter wire connected to the small terminal on the alternator. This may be the root of your problem. If you have 12V at the alternator, that's coming from the battery connection. Try running a wire directly to the small terminal of the alternator from BAT + and see if you get 14.3V then with the car running. Either the bulb is out or you have a problem with the power feed on the green exciter wire that runs through the bulb to the alternator.
 
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