battery drain - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 13 Old 03-03-2018, 07:41 AM Thread Starter
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battery drain

1991 mustang lx.. battery keeps needing to be charged. car was not driven in 2 years. ran fine before storage. charged battery and it keeps needing to be recharged...

disconnected neg battery cable and connected test light between ground and disconnected ground cable.

battery is in trunk.

light glows brightly.

disconnected all wiring from solenoid in engine compartment where battery cable from battery in trunk goes to. so nothing should be connected to battery now.

still glows...

I'm thinking somehow??? the battery cable is shorting to ground. thus the drain. if everything (loads) are disconnected from the battery cable then the light should not be on, correct? just checking...

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post #2 of 13 Old 03-03-2018, 08:02 AM
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Sounds like you are on the right track. Trace the cable(s) and see what you come up with, as painful as that may be.


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post #3 of 13 Old 03-03-2018, 11:59 AM
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battery cable short to ground, no

you would have a fire

your test light to ground was flawed, your test light completed the circuit

redo tests?

89 GT gr-40, KB2200(10psi), tweecer R/T,LC-1, 22gal cell, w/tailpipes.
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post #4 of 13 Old 03-03-2018, 03:10 PM Thread Starter
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Quote:
Originally Posted by indy2000 View Post
battery cable short to ground, no

you would have a fire

your test light to ground was flawed, your test light completed the circuit

redo tests?
if the positive cable isn't connected to anything (load) in the engine compartment there wouldn't be any circuit to complete, correct?

its been a few years, but pretty sure i ran the positive cable from the battery in trunk, directly to the starter solenoid post in the engine compartment, which is where i disconnected it... i get 12.6 volts at that cable when i test it, and its disconnected from the cars electrical system as far as i can tell... so not sure why my light is "lighting", because that would indicate a draw, and a complete circuit somewhere...

weird...
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post #5 of 13 Old 03-03-2018, 04:08 PM
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you know there are circuits hot all the time

you remove neg off of batt and measure you will see a 12 volt drop

not weird at all

you can have circuits back feed through loads all the time normal

you need to measure actual current to to find the draw effectively

shall we test?

i do elec diag for a living and for fun

89 GT gr-40, KB2200(10psi), tweecer R/T,LC-1, 22gal cell, w/tailpipes.
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post #6 of 13 Old 03-03-2018, 04:37 PM Thread Starter
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Quote:
Originally Posted by indy2000 View Post
you know there are circuits hot all the time

you remove neg off of batt and measure you will see a 12 volt drop

not weird at all

you can have circuits back feed through loads all the time normal

you need to measure actual current to to find the draw effectively

shall we test?

i do elec diag for a living and for fun
ok, so:

1. battery is in trunk.
2. neg cable from battery goes to frame ground by quad shock.
3. positive cable goes from battery to isolated stud in trunk. 3' of cable between stud and battery.
4. then from that "+" stud in trunk approx 15' of cable to starter solenoid, where all the cars 12v fusible links tie into just like from the factory.
5. connecting amp meter between neg battery stud and negative battery cable, i see a .25-.32 amp reading on the meter.
NOTE: the test light will also light if i substitute the amp meter for the test light.
6. when i isolate the "+" terminal on the starter solenoid, so it is not hooked up to any wiring, i still see the draw, and the light goes on.
7. when i disconnect the positive battery cable in the trunk, isolating the 15' of cable between the trunk and the starter solenoid, amp meter shows no draw (0.00) and the test light goes out.
-if i reconnect just the isolated 15' of cable between the trunk and the starter solenoid(all wires disconnected from the starter solenoid) the draw comes back and the test light will light.

NOTE: i am not using the meter and test light at same time, just one or the other

this would indicate to me there is something drawing a load between the trunk positive post and the end of that 15' of wire.

just not sure why this is happening. my only thought is unless its grounded somewhere in that 15' of wire....

any thoughts appreciated, this is weird, at least to me...
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post #7 of 13 Old 03-03-2018, 05:10 PM
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test light does not substitute as a amp meter........

where did you get that???

you need to think this out, you are not clearly

a test light is a load, NOT a current measure, if your test light is 1 amp, the circuit can support 1 amp

so be clear here

lets use your amp reading

while the amp meter is ON, start removing one circuit at a time, at the fuses or link at the power distribution

once you see near 50-100mA that last circuit is the problem

the ecm needs power all the time, so does the stereo

89 GT gr-40, KB2200(10psi), tweecer R/T,LC-1, 22gal cell, w/tailpipes.
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post #8 of 13 Old 03-03-2018, 05:35 PM Thread Starter
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Quote:
Originally Posted by indy2000 View Post
test light does not substitute as a amp meter........

where did you get that???

you need to think this out, you are not clearly

a test light is a load, NOT a current measure, if your test light is 1 amp, the circuit can support 1 amp

so be clear here

lets use your amp reading

while the amp meter is ON, start removing one circuit at a time, at the fuses or link at the power distribution

once you see near 50-100mA that last circuit is the problem

the ecm needs power all the time, so does the stereo
ok, so nothing is connected to the battery feed in the engine compartment. everything is disconnected and the amp meter shows a reading of .25-.32 amps...
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post #9 of 13 Old 03-03-2018, 07:03 PM
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are those all the circuits in the car?

89 GT gr-40, KB2200(10psi), tweecer R/T,LC-1, 22gal cell, w/tailpipes.
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post #10 of 13 Old 03-04-2018, 06:49 AM Thread Starter
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are those all the circuits in the car?
yes, the positive battery cable running from the trunk to the engine compartment is not connected to any circuits. totally disconnected from the cars electrical loads. still shows a current draw on the amp meter.

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post #11 of 13 Old 03-04-2018, 09:01 AM
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Quote:
Originally Posted by bustangs View Post
yes, the positive battery cable running from the trunk to the engine compartment is not connected to any circuits. totally disconnected from the cars electrical loads. still shows a current draw on the amp meter.
either

you still have a load that you missed

or your meter is not good

or your battery is faulty

do you have another battery to try, to eliminate variable?

89 GT gr-40, KB2200(10psi), tweecer R/T,LC-1, 22gal cell, w/tailpipes.
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post #12 of 13 Old 03-06-2018, 05:35 AM Thread Starter
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Quote:
Originally Posted by indy2000 View Post
either

you still have a load that you missed

or your meter is not good

or your battery is faulty

do you have another battery to try, to eliminate variable?

don't think i missed anything.
cable goes from the trunk to the engine compartment.
battery is new optima red top.
tried 2 different meters.

just going to put a switch in trunk for now/future. get some new cable and re-run the wire.
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post #13 of 13 Old 03-06-2018, 09:42 AM
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the ecm needs to be powered all the time

89 GT gr-40, KB2200(10psi), tweecer R/T,LC-1, 22gal cell, w/tailpipes.
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