Need Help diagnosing electrical problem

[fv22]

Hi Everyone!
I'm a new member looking for help. Thanks in advance for reading this and for any help/suggestions with the problem

1996 V6 explorer 2wd.
Yesterday morning went out to vehicle and battery was dead. Checked with voltmeter had about 4 volts. Battery a few years old and never had a problem before. Battery terminals were pretty badly corroded so first step was to remove and do a good cleaning of terminals and top of battery

Charged for several hours to bring to 12.5 volts. Load tested with 50 amp load, held about 10.5-11 volts for over 10 seconds. Hydrometer test each cell all balls floating. Check voltage a few seconds after load test just over 12volts. This all leads me to believe battery is good.

Started engine check voltage at idle, 13.4, bring engine to about 1800 rpm voltage now 14-14.1. This leads me to believe charging system is good.

Then check for obvious problems such as dome light on, glove box light, fuel pump running etc. but no to all. Figured was just due to bad connection from corroded terminal ends so after battery was charged I used vehicle for some running around I had to do, worked fine all day.

This morning battery was dead again. :-(

Went through same charging and testing routine as yesterday with same results, battery tests good as does charging system so I now start to look further.

Disconnect positive terminal end from positive terminal and connect voltmeter from battery terminal to positive terminal end, voltmeter reads battery voltage. This leads me to believe there is a short to ground.

With positive terminal end still disconnected from positive terminal and voltmeter still connected between positive battery terminal and positive terminal end I remove fuses 1 by 1 to see if voltage goes to zero indicating I found the circuit with the problem. I R&R every fuse, relay and breaker from interior and under hood fuse panels with no difference, voltmeter still reads battery voltage.

Did visual inspection of as much of wiring as I can see with no obvious defect. After some thinking the only thing I can come up with is a bad ignition switch(???). Does anyone have any thoughts if this could be correct or know of something else that may cause the problem before I buy and replace switch?

Again I thank you in advance for any help or suggestions.
Regards,
Bob

 

[2000StreetRod]

Kam

There will always be a small flow of current for the PCM keep alive memory, radio clock, GEM, message center, etc. They don't all use the same fuse or relay. You need to measure current flow and then determine which fuse or relay significantly reduces the flow.

 

[fv22]

2000StreetRod
Thanks for the reply. The question I have is why would there be battery voltage between a disconnected positive terminal end and the positive terminal of the battery all the time. I have removed each fuse, breaker and relay 1 at a time and the voltage never dropped. I thought it would have dropped when one of them was removed but never happened. Leads me to believe a short, just done know where since I was not able to pin it down to a particular circuit.

 

[2000StreetRod]

multiple paths to ground

Since there are multiple devices consuming power in low amounts that have multiple paths to ground disconnecting only one circuit still leaves others functional.

Some candidates for higher current flow: sticking power seat control; defective heated seat module; sticking door lock or unlock relay; defective battery saver relay; defective DRL module; sticking brake pedal position switch; short in generic electronic module; sticking rear window defrost relay; short in EATC module; or defective electric shift control module.

You need a 1996 electrical wiring diagram to determine which circuits have power at all times and how a defective module or relay would affect current flow and a way to measure current. The current measuring capacity of your voltmeter is probably limited to 10 amps which is insufficient. You could place a high power, low resistance resistor between the positive post and cable terminal, measure the voltage drop across it and calculate the current flow. I = E/R. Then pull relays and fuses until there is a signficant reduction in current flow.

 

[Runnin'OnEmpty]

......
Disconnect positive terminal end from positive terminal and connect voltmeter from battery terminal to positive terminal end, voltmeter reads battery voltage. This leads me to believe there is a short to ground.......

With this connection you're reading the battery
potential which is 12v or thereabouts. If you do
the same multimeter connection and turn the tester
knob to the amps scale, you'll read the discharge
current. IIRC, it should be around 6ma. For the
battery to discharge to 4v overnight, you would have
a very big drain, much more than 6ma...

 

[thorney_5]

With this connection you're reading the battery
potential which is 12v or thereabouts. If you do
the same multimeter connection and turn the tester
knob to the amps scale, you'll read the discharge
current. IIRC, it should be around 6ma. For the
battery to discharge to 4v overnight, you would have
a very big drain, much more than 6ma...

x2

You need to perform the same test (pull fuses 1 by 1), but with the meter on the AMPS scale. This will show which circuit is drawing excessively from your battery. Volts mean nothing with a parasitic draw... It will always show 12ish.... It's all about amps.

 

[fv22]

Great info, thanks everyone who submitted. It will have to sit for a few days until I get another look at it but now I have more to look for.