yo Here is da skinny by Henry J;
Drain Testing
Check for current drains on the battery in excess of 50 mA with all the electrical accessories off and the vehicle at rest. Current drains can be tested with the following procedure.
WARNING: DO NOT ATTEMPT THIS TEST ON A LEAD-ACID BATTERY THAT HAS RECENTLY BEEN RECHARGED.
CAUTION: Do not crank the engine or operate accessories that draw more than 10A. You could blow the fuse in the meter.
Many computers draw 10 mA or more continuously.
Use Rotunda 88 Multimeter 105-R0053 or equivalent between the battery positive or negative post and its respective cable.
see Diagram j6432a at end of my reply
NOTE: Steps 1-5 correspond to the numbers in the following illustration.
Insert the test leads in the input terminals shown.
Turn switch to mA/A DC.
Disconnect battery terminal and touch probes as shown.
Isolate circuit causing current drain by pulling out one fuse after another while reading the display.
Current reading will drop when the fuse on the bad circuit is pulled.
Reinstall fuse and test components (including connectors) of that circuit to find defective component(s).
Typically, a drain of approximately one amp can be attributed to an engine compartment lamp, glove compartment lamp, or luggage compartment lamp staying on continually. Other component failures or wiring shorts may be located by selectively pulling fuses or disconnecting fuse links to pinpoint the location of the current drain. When the current drain is found, the test lamp will go out or the meter reading will fall to an acceptable level. If the short is still not located, after checking all the fuses and fuse links, the drain may be due to the generator.
Test Conclusion
The current reading (current drain) should be less than 0.05 amps. If it exceeds 0.05 amps it indicates a constant current drain which could cause a discharged battery. Possible sources of current drain are vehicle lamps (underhood, glove compartment, luggage compartment, etc.) that do not shut off properly.
If the drain is not caused by a vehicle lamp, remove the fuses from the interior fuse junction panel, one at a time, until the cause of the drain is located. If drain is still undetermined, remove fuses one at a time at the main fuse junction panel to find the problem circuit.
Electronic Drains Which Shut Off When the Battery Cable Is Disconnected
Repeat Steps 1 through 6 of the voltmeter drain testing.
Without starting engine, turn ignition on for a moment and then off. If applicable, wait one minute for the illuminated entry lamps to turn off.
Connect the voltmeter and read the voltage.
Test Conclusion
The current reading (current drain) should be less than 0.05 amps. If it exceeds 0.05 amps after a few minutes, and if this drain did not show in previous tests, the drain is most likely caused by a malfunctioning electronic component. As in previous tests, remove the fuses in interior fuse junction panel one at a time to locate the problem circuit.
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Parasitic Draw; Diodes inside the alt could be shorted, thus causing drain, but the it would still put out 12 Volts, and pass the Voltage Output Test, however it could not put out full current, and would fail the Current Load Test.Remove & Charge Battery and take voltage reading (should be around 12.6 volts). Disconnect alternator, then re-install battery for a day or so & then check batty voltage again; if no drain, then diodses are prob the issue. or Take alt it to a parts store where they can BENCH-test it for free. BTW, The voltage should be between 13.0 and 15.0 volts w/engine idling.
Generator On-Vehicle Tests (this is what a dealer service tech or shop would do; get it done for free somewhere)
Troubleshooting or diagnosis is required before actual service can be made in the electrical system. Even where an obvious condition makes replacement of a component necessary, find out why the component failed. When a condition is diagnosed correctly, unnecessary service is prevented, the time the vehicle is out of service will be decreased, and the condition will be properly corrected the first time.
In order to check the charging system, the use of Rotunda Alternator, Regulator, Battery and Starter Tester (ARBST) 010-00725 or equivalent tester is suggested.
When performing charging system tests, turn off all lamps and electrical components. Place transmission in neutral and apply parking brake.
CAUTION: Do not make jumper wire connections except as directed. To do so may damage generator (GEN) (10346).
CAUTION: Do not allow any metal object to come in contact with the housing and internal diode cooling fins with key on or off or short circuit will result and burn out diodes.
NOTE: Battery posts and cable clamps must be clean and tight to ensure accurate meter indications.
Load Test
Switch the Rotunda Alternator, Regulator, Battery and Starter Tester (ARBST) 010-00725 or equivalent to the ammeter function.
Connect the positive and negative leads of the Rotunda Alternator, Regulator, Battery and Starter Tester (ARBST) 010-00725 or equivalent to the battery (10655).
Connect the current probe to the generator B+ output lead, Circuit 38 (BK/O). On Mitsubishi 215 ampere generator, use Circuit 605R.
With the engine running at 2000 rpm, adjust the Rotunda Alternator, Regulator, Battery and Starter Tester (ARBST) 010-00725 or equivalent load bank to determine the output of the generator. Generator output should be greater than the graph shown below. If not, refer to the Symptom Chart in the Diagnosis and Testing portion of this section for diagnostic procedures.
see graph j5696a
No-Load Test
Switch the Rotunda Alternator, Regulator, Battery and Starter Tester (ARBST) 010-00725 or equivalent to the voltmeter function.
Connect the voltmeter positive lead to the generator B+ terminal and the negative lead to ground.
Turn all electrical accessories off.
With the engine running at 2000 rpm, check the generator output voltage. The voltage should be between 13.0 and 15.0 volts. If not, refer to the Symptom Chart in this section for diagnostic procedures.
Generator Bench Tests (Integral Rear Mount Regulator, Internal Fan Generator)
NOTE: The integral rear mount regulator � internal fan type generator (GEN) (10300) is serviced as an assembly only.
Replace generator as required after performing generator on-vehicle tests. Refer to Section 14-02B.
Capacitor
The radio voltage regulator capacitor (18832) connected across the heat sinks may be tested on a capacitor tester if available. Its value is .158 MFD, and 100 working volts DC.
In the absence of a capacitor tester, the unit may be checked for shorts by means of an ohmmeter connected across the terminals. A reading under 20 milli-ohms indicates a shorted or leaking radio voltage regulator capacitor which should be replaced.
Parasitic Current Drain Test; "...you should be able to trace the "parasitic draw" on the battery in the normal way. Pull the (-) cable off & put an ammeter inline set to the 10A range (or higher if possible) to see how much current is being pulled out of the battery with the key OFF, the doors SHUT, & the hood light bulb REMOVED. Make sure absolutely NOTHING is turned on anywhere on the truck. If it registers 0 or below the meter's next range, switch it down a range until it shows some useful numbers. If it ends up being below 0.5A (500mA), then replace the battery. If it's above that, start by disconnecting all the alternator wires & see if the reading drops under 0.5A. Then move to the fuse block & pull them 1 at a time until there's a significant drop in the reading. That's the circuit that's draining the battery. Follow it to find the problem..."
Source: by Steve83 (Steve, That dirty old truck) at FSB
With any luck your just having a batter issue, or you can find a stuck light or something along those lines, i wasnt so lucky.
