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98 Concours 212,000 orginal motor,trans
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160 Posts
Discussion Starter #1
So I just installed my alternater and I get no voltage from the alternator and a code that says P1638 - Generator F-Terminal Circuit. Thats it! Any idea whats going on, bad alternator or something on the car. I tested the output cable to the battery and its only showing 11 volts which i would assume is from the battery. Last night while I had the batter out of the car I wanted to get my cd's outta the changer so I hooked up the 12 amp battery charger and that gave me enough just to get the cd's out of the changer. Could I have ****ed up something or is the alternator just bad.
 

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94 ETC,97 STS
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3,531 Posts
Someone posted a while ago that some alternators are missing a wire. I don't remember the details. You can look through tech tips or possibly someone remembers the post.
 

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White Diamond '03 DHS (with DTS floor shift)
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Was it an A/C Delco alternator? I recall someone at caddyinfo had a problem similar to this. He used an aftermarket alternator. Logan said that some of them don't have the proper circuitry for the PCM to recognize its presence. He replaced it with an A/C Delco and all was well.
 

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The Northstar Tuner
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2,759 Posts
What kind of car is it?
E cars, KD, KE & KF 96 to 99 & 96 & 97 Seville's are IPC Turned on Alternators.

98 & 99 Seville's are PCM controlled.

00+ are PCM controlled also
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98 Eldo info
Charging System Operation
The generator provides voltage to operate the vehicle's electrical system and to charge its battery. A magnetic field is created when current flows through the rotor. This field rotates as the rotor is driven by the engine, creating an AC voltage in the stator windings. The AC voltage is converted to DC by the rectifier bridge and is supplied to the electrical system at the battery terminal.

When the ignition switch is placed in the RUN position, voltage is supplied to generator terminal L by the instrument cluster, turning on the regulator. The generator's voltage regulator controls current to the rotor, thereby controlling the output voltage. The rotor current is proportional to the electrical pulse width supplied by the regulator. When the engine is started, the regulator senses generator rotation by detecting AC voltage at the stator through an internal wire. Once the engine is running, the regulator varies the field current by controlling the pulse width. This operation regulates the generator output voltage for proper battery charging and electrical system operation. The generator F terminal is connected internally to the voltage regulator and externally to the PCM. The PCM monitors the field voltage on the generator F terminal.

1999 Cadillac Seville
Charging System Circuit Description
The generator provides the voltage to operate the vehicle's electrical system and to charge the battery through CKT 1 (RED). When the ignition switch is placed in the RUN position, voltage is supplied to generator terminal L by the PCM, turning on the regulator. The generator's voltage regulator controls current to the rotor, thereby controlling the output voltage. The rotor current is proportional to the electrical pulse width supplied by the regulator. When the engine starts, the regulator senses generator rotation by detecting AC voltage at the stator through an internal wire. Once the engine is running, the regulator varies the field current by controlling the pulse width. This technique regulates the generator output voltage for proper battery charging and electrical system operation. The generator F terminal is connected internally to the voltage regulator and externally to the PCM. The PCM monitors the field voltage on the generator F terminal.

The PCM turns on the charge indicator by sending a Class 2 message to the instrument cluster whenever undervoltage, overvoltage, or a stopped generator is detected by CKT 225 (RED).
 

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Registered
98 Concours 212,000 orginal motor,trans
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160 Posts
Discussion Starter #6
It is an a/c delco alternator. I had the bearings go out in and I took it in and had the bearings replaced, also the voltage regulator and the front housing. I own a 98 deville concours. I'm inclined to think that I may have blown the alt fuse when I plugged in the battery charger without the battery being in the car.
 
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