02 Chevy prizm The alternator bench tested good as does the battery. When regulator harness is plugged in and battery disconnected the car dies, unplug the harness and car will continue to run.

Sounds like the the alternator go surged or shorted, probably burned out the regulator inside the alternator. Remove the alternator and have it bench tested at the parts store, you may have damaged the battery also, you may want to take it with you and have the parts store load test it.

a faulty alternator will most likely be the problem
check drive belt condition and tension
Remove the alternator and have ir bench tested for regulator and rectifier block

possible a bad regulator. Some alternators have the regulator as part of the alternator and others have it separate. If you did not have the alternator bench tested but simply used a multimeter to check voltage then it is possible that the alternator is not good as you can have 14.5 volts out put but it could be ac current as a rectifier is bad.

The early GM products would build up restance in the wire that went from the alternator to the starter. The easy cure for this is to install a 10 guage wire directly from the Alternator Batt. lug directly to the battery postive post. Do this using the correct end connectors.. do not just wrap the wire around the termanel. This was a big problem on these cars. especially the Diesel cars. Always disconnect the battery ground terminal before you work on this.

Possibly a bad fuse which is not allowing the power from your new alternator to make it back to the battery. Do you have alternator voltage making it to the battery when running?

possible that the mechanic who sis not auto electrical qualified has damaged the alternator when fitting it of has fitted the wrong unit ( internal voltage regulation as opposed to external voltage regulation) take it to an accredited auto electrician for a bench test , have the voltage regulator tested and load test the battery as well
batteries can be defective for manufacture

• TESTING
• REMOVAL & INSTALLATION

Alternator

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TESTING

The easiest way to test the performance of the alternator is to perform a regulated voltage test.

1. Start the engine and allow it to reach operating temperature.
2. Connect a voltmeter between the positive and negative terminals of the battery.
3. Voltage should be 14.1-14.7 volts.
4. If voltage is higher or lower than specification, connect a voltmeter between the battery positive (B+) voltage output terminal of the alternator and a good engine ground.
5. Voltage should be 14.1-14.7 volts.
6. If voltage is still out of specification, a problem exists in the alternator or voltage regulator.
7. If voltage is now within specification, a problem exists in the wiring to the battery or in the battery itself.

Many automotive parts stores have alternator bench testers available for use by customers. An alternator bench test is the most definite way to determine the condition of your alternator.

REMOVAL & INSTALLATION

1993-94 Models
See Figures 1 through 5

1. Disconnect the negative battery cable, for safety purposes.
2. Remove the right side splash guard from under the vehicle.
3. Disconnect the alternator lead wires and connections. Label them if you are unsure of their locations.

Fig. Fig. 1: The large positive lead connection is protected by a rubber boot

Fig. Fig. 2: Make sure the alternator ground wire is also removed

1. Loosen the drive belt adjusting bolt and slip the belt off the pulley.
2. Remove the lower adjustment bolt, followed by the upper pivot bolt.

Fig. Fig. 3: Remove the lower adjustment bolt ...

Fig. Fig. 4: ... followed by the upper pivot bolt. Make sure you support the alternator

1. Lower the alternator from the vehicle.

To install:

1. Using a C-clamp and a socket, push the upper pivot bushing back in it's bore until it bottoms out.

Fig. Fig. 5: Using a C-clamp to push in the pivot bushing will make installation easier

1. Raise the alternator into the engine bracket, and push the upper pivot bolt all the way through the bracket to support it.
2. Install the lower adjustment bolt, followed by the upper pivot nut.
3. Place the belt on the alternator pulley, and tighten the belt.
4. Tighten the upper and lower mounting bolts.
5. Engage the alternator lead wires and connections.
6. Connect the negative battery cable.
7. Start the vehicle, and check for proper operation.
8. Readjust the belt tension, if necessary. Install the lower splash guard.

1995-98 Models

1. Disconnect the negative battery terminal.
2. Remove the splash guard on the right side of the vehicle.
3. Loosen the alternator belt idler pulley.
4. Slip the drive belt off the alternator pulley.
5. Remove the four air conditioning compressor mounting bolts.
6. Remove the radiator fan and fan shroud.
7. Move the air conditioning compressor forward.
8. Disconnect the alternator harness connector.
9. Remove the alternator mounting bolts, and lower the alternator from the vehicle.

To install:

1. Hold the alternator in place and install the mounting bolts.
2. Plug in the alternator harness connector.
3. Move the air conditioning compressor back into location.
4. Install the radiator cooling fan and shroud.
5. Install the air conditioning compressor mounting bolts.
6. Place the drive belt on the alternator pulley.
7. Tighten the drive belt to the proper tension with the idler pulley.
8. Install the splash guard.
9. Connect the negative battery terminal.

Proper belt tension is important. A belt that is too tight may cause alternator bearing failure; one that is too loose will cause a gradual battery discharge and/or belt slippage, resulting in belt breakage from overheating.

First off, disconnecting athe battery while the engine is running is the quickest way to damage an alternator. Unlike the old DC generators, the alternator needs the battery in circuit to protect it against voltage runaway.

If the alternator has been bench-tested and seems to be functional, I would start by verifying the related vehicle circuits. Witch a DC voltmeter, start out by measuring the voltage at the alternator's output terminal, the heavy black/orange wire. It should be full battery voltage. If it is anything less than battery voltage, you must determine why. Some things to look at are the gray 12-gauge fusible links A & B, and the various splices and connections in the circuit (see diagram below).

Next, disconnect the voltage regultor harness plug from the alternator and check the voltage at the wiring harness regulator plug's "A" terminal connector - the yellow/white wire. It too should be full battery voltage. If it is anything less than full battery voltage, you must determine why. In this case, look at the 20-amp ALT fuse in the battery junction box, and at the various splices and connectors in that circuit.

Then, turn the key switch to its "RUN" position and measure the voltage
at the wiring harness regulator plug's "I" terminal connector - the light green/red wire. It should be somewhere between 8 and 12 volts. If there is no voltage present, check Fuse 5 (15 amps) in the main fuse panel and the various connections in that circuit.

The final test is to measure the voltage between the batterty positive terminal and the alternator housing or frame. If it is anything less than full battery voltage, check the alternator mounting.

Sounds like the battery dies, or the alternator has stopped charging and the battery lasted as long as it could. Battery water, voltage while off and then while running if you can jump it.If you think the battery is good, take the alternator off and take it to the parts store and test it, if it is neither of those 2 , then the computer died. Check it out.

Yes, you would need to inspect for loose wires, etc. Also, consider pulling the alternator and get it bench tested.

Typically what fails are called DIODES. These are one way valves for electricity. They fail, eventually and cause a drain to ground. There are ones dedicated to firing off the regulator. My guess would be this area.

More commonly a problem with the alternator, less with wiring, but anything is possible. Bench test will help you to know...

Doc