ok so my car is not charging the battery. The alternator was taken off car and in taken to oreillys and autozone both preformed a test which showed the alt. to be good. I have cleaned and reconnected the solnoid contacts. I also ran a wire straight from the back of the alt to the battery still not charging system. any thoughts any help appriecated. thx oscar

 

Just a guess but have you checked the grounds? Both on the battery and on the alt. The big red wire is only 1/2 the circuit. Do you see 14V on the alternator terminal but still 12V at the battery? If so either the positive or negative is eitehr disconnected or high resistance due to a bad connection or damaged conductor.

 

BREAK OUT THE DC Volt meter!!!!!!!!!!!!!!!

Measure the battery voltage on ALL the terminals that connect to the battery and starter solenoin!!!! There are several FUSABLE LINKS that can be bad.

Heres the schematic that you need to trouble shoot!

 

I've had alternators check out at the parts store and be bad, you need a scope to see if your getting true DC out of it. I also had one that tested fine but had a short to the case, discharged the battery is about a day. Bet your alternator really is sick. What voltage do you get at the battery (with a Digital Volt meter)?

 

With the engine OFF you should have actual battery voltage on ALL the terminals that are contacted to the battery

When the engine is running, you should see charging voltage on the same terminals. Usually it around 13.5-14.5 VDC

 

HI Bill, need more help please I checked the bigger wire on the alt. and have 12.5 volts with the car off and also on D red wire on the 3 wire plug connecting to the alt. that its self also shows 12.5 with car off. question what should I be seeing on B and C which is the red and gray wire on the small plug. Should I be seeing 12.5 with the key ion ing. on B which says its the generator turn on signal? any more help appricated thx oscar

 

HI, with the car on the voltage steadily drops below 8 which makes the car start to die out there is no charging from the alt to the battery. I have good connection from the battery to the alt and grounds look to be good also. I can get good low resistance thru the grounds.

 

Check terminal B (the small red wire) on the connector. When the engine is running, there should be a generator TURN ON signel there sent by the PCM. Ive never actually checked the signal / voltage so I cant tell you what it actually is. It will be a DC Voltage and something between 5 VDC and battery voltage.

Here is how the charging system works:

Document ID# 715581
2001 Chevrolet/Geo Corvette


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Charging System Description and Operation
Generator
The Valeo generator is electrically similar to earlier models. The generator features the following major components:

The delta stator
The rectifier bridge
The rotor with slip rings and brushes
A conventional pulley
The regulator
The pulley and the fan cool the slip ring and the frame.

The generator features permanently lubricated bearings. Service should only include tightening of mount components. Otherwise, replace the generator as a complete unit.

Regulator
The voltage regulator controls the rotor field current in order to limit the system voltage. When the field current is on, the regulator switches the current on and off at a rate of 400 cycles per second in order to perform the following functions:

Radio noise control
Obtain the correct average current needed for proper system voltage control
At high speeds, the on-time may be 10 percent with the off-time at 90 percent. At low speeds, the on-time may be 90 percent and the off-time 10 percent.

Circuit Description
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 engine is running, the generator turn-on signal is sent to the generator from 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 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 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. When the voltage regulator detects a charging system problem, it grounds this circuit to signal the PCM that a problem exists. The PCM monitors the generator field duty cycle signal circuit. The system voltage sense circuit receives B+ voltage that is Hot At All Times through a fuse link that is connedted to the starter.. This voltage is used by the regulator as the reference for system voltage control.

Charging System Indicator(s)
CHARGE SYSTEM FAULT
The IPC illuminates the CHARGE SYSTEM FAULT indicator in the message center when the following occurs:

The PCM detects that there is a problem with the electrical charging system. The IPC receives a class 2 message from the PCM.
If the tachometer is less than 500 RPM and the power mode state is in the crank mode then this message will not be displayed. Instead the CHECK GAGES indicator will illuminate.
HIGH VOLTAGE
The IPC illuminates the HIGH VOLTAGE indicator in the message center when the IPC detects that the ignition is in RUN and battery voltage is greater than 15.75 V for more than 5 seconds.

LOW VOLTAGE
The IPC illuminates the LOW VOLTAGE indicator in the message center when the IPC detects that the ignition is in RUN and battery voltage is less than 10 V for more than 5 seconds.


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Document ID# 715581
2001 Chevrolet/Geo Corvette

 

Thanks Bill, I troubleshot everything and it all came back to the alt. so I bought one and that was what was wrong. even tho the old still tested good again at the auto parts store when they checked it for the return core. Thx Oscar

 

See, thought it was the alternator-I think the alternator tests at the parts stores are almost worthless anymore.