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· Chrome gets me home
2,963 Posts
Discussion Starter · #1 ·
i dont drive the bronco as much as i should but when i do want to its been dead lately. :banghead i have an Optima redtop that i will put on a charger for a day and it works great, if i let the truck sit for longer than 2-3 days without starting it it drains it completely.

Is there anything i can do to try and locate the power draw? currently there is nothing hooked up to the battery other than the positive/negative amp or lights or anything.
i appreciate the help in advance:beer

· Premium Member
4,628 Posts
Remove a cable, and bridge it with an electrical tester to see how much, or if any power is going between them.
That will eliminate that the battery itself is draining it self, there is a acceptable amount of draw as well. Dont start it like that thought.

· Chrome gets me home
2,963 Posts
Discussion Starter · #7 ·
thanks guys im gonna have to wait for a couple days till i go buy a tester. i want to say this is a more recent problem. but id be lying, it started when i stopped driving the truck every day or at least starting it.

· Registered
612 Posts
i had an issue with this on my 89. what i had to do was buy a 4gauge switch, ran it into my cab for a battery kill switch. i then had to run a new aux line to my radio for memory that bypassed the kill switch * i got sick of resetting my radio stations every morning * it was a pain, and still is a pain over a year later, but as i tested my battery and it was fine, and im not much of a wire chaser its all i could do :) 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.

· Registered
612 Posts
for your radio memory to kill your battery, you would have to let it sit, for months. we have a 90 something buick we use as storage *packed with old clothes for our kids* i hadnt touched it in at least 4-5 months, went out to fire it up and it started right up, albeit really weak turning over.

· Super Moderator
33,867 Posts
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.

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.

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.

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; " 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


· Registered
3 Posts
Hi Jslax04,
There has already been a lot of good advise given. I must say, miesk5's post is as complete a testing post as I have ever seen, good stuff. We have a YouTube video that also explains the procedure for measuring a parasitic draw.
Your Optima may have suffered some sulfation since it seemed to start when you quit cranking the truck regularly. If so, that could effect it's ability to hold a charge. Try charging it at 10 amps, keeping an eye on it to be sure it doesn't become hot to the touch or start emitted a fume. Do this for a couple hours then continue charging at a lower rate until it is at full charge (about 12.6-12.8 volts for a RedTop). The 10- amp charge may break up some of the sulfation.
This link helps explains sulfation.
Hopefully this isn't the problem and you will find that is has a parasitic drain easily fixed and that solves the problem.
Like someone else suggested, be sure the battery is fully charged and then see, if unhooked, it will hold close to that voltage level for 12-24 hours.
If I can help further or answer questions about our products, feel free to ask,
Bill Howell
eCare Manager, OPTIMA Batteries, Inc.
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