My battery drains overnight

[Masato]

Can somebody figure this out?

There's a short in the electrical system but i can't find it. It damages the alternator too often, thank Pep Boys for their lifetime warranty.

I pulled the complete wire harness from under the dash and checked it, checked the ign sw, the horn, wiper sw, light sw, int lights, disconnected the radio and cigar lighter, everything is in order. Pulled the complete wire harness from the engine compartment, everything OK.

Disassembled the fuse block, not there. When i check resistance from ground to the two spade terminals in the alternator, resistance is zero, but don't know if this is normal.

Several electric shops have checked it and can't find what's causing the battery to drain. The closest one shop got was to install a small lamp in series between the alternator and the resistor wire, which cured the problem for a while.

I hope somebody can help me before i settle for a battery disconnect like the ones in race cars, which will mean defeat.

[Don S]

..
Masato
… My Cruise Control on-off switch if left on can do the same thing. I have seen a dome-light bulb painted black. I have seen heater-motors connected to the starter solenoid. Have you tried disconnected the alternator/regulator? Do you have a block-heater? I had one that the brake lights would come on ten minutes after you left the car.

Good Luck ;) and CUL.. Don S..

[Joe Guilbeau]

Masato,

If the vehicle is back together, here is how to troubleshoot the battery drain problem.

Fully charge the battery and get an meter that reads DC Amps, put this meter between the negative battery cable and the negative battery terminal.

Give us the amps that the meter reads.

I don't know what kind of alternator that you are using, but getting zero ohms between any terminal and the case sounds like it is not designed to operate that way.

The spade lugs are probably sense terminals that the alternator uses to provide the regulator some idea of what the battery situation is. Having a resistance wire run to the sense terminals, with a lamp in series, suggests a Delco alternator?

Anyway, while the battery is draining you can remove all wires from the alternator, if this stops the battery drain, well you have isolated the problem to either the wiring to/from the alternator or the alternator itself.

If the drain continues, then start removing fuses. If the short is on a fused circuit, then it should stop draining the battery when you pull that fuse, and you have isolated the short to the system that this particular fuse protects.

Check that amp drain again, from your description it may be that the drain is less that the fuse that protects it, like a 7 amp drain on a 10 amp fused circuit.

In any case, if you isolate it to a fused circuit, get a circuit breaker that is rated at less than the current drain, for instance; a 7 amp drain, get a 5 amp breaker.

Once you insert the proper circuit breaker in the fuse block to replace the fuse it will start clicking on and off as it opens and closes.

Now you need something to measure the current in a wire without opening up that wire.

When the current in the wiring associated with the system with the short begins to flow or abruptly stops, due to the circuit breaker closing or opening, a magnetic field will be created around the wire that has a shorted section in it, if indeed that actually exists.

Shops sell a hand held guage that is very sensitive to magnetic fields, and will deflect the meter when held in proximity to the wire with the short in it.

Run this along all of the routing of the circuit that the short is in, and the meter will begin to deflect as you get near the wire that has been draining your battery.

Now, as you move the meter along the wire harnesses, sooner or later the deflection on the meter will be much less, this is the area that the short is in.

Make any sense?

Simpler explanations are usually the answer, so try not to complicate the issue too much, unlike much of this post, I suppose!

Be methodical and logical in your troubleshooting procedures, since the alternator is giving you issues, most likely your problem is associated with it, try and think back to when this started happening, as there is usually a cause and effect clause in the Universe.

[Wesdog]

Masato,

What year and model vehicle do you have? What model alternator are you using? If it is a Delco, the resistor wire should be connected between ignition switched power and terminal #1 (white wire) on the alternator. Terminal #2 (red wire) is connected to unswitched battery voltage, usually the starter relay battery post. Make sure the plug is wired correctly and mated correctly to the alternator.
Is your starter relay installed and connected correctly? There is a difference between the battery post and starter post. The starter post is wired internally to the small terminal that connects to the ignition system to provide full battery voltage to the coil during cranking. If the battery cable is connected to the starter post of the relay it will be providing battery voltage to the ignition system without the starter relay engaged and will drain your battery. Measure the voltage between the small terminals of the starter relay and battery negative with the ignition off, should be 0 volts.

[xc_xtc]

Originally posted by Wesdog:
Masato,

What year and model vehicle do you have? What model alternator are you using? If it is a Delco, the resistor wire should be connected between ignition switched power and terminal #1 (white wire) on the alternator. Terminal #2 (red wire) is connected to unswitched battery voltage, usually the starter relay battery post. Make sure the plug is wired correctly and mated correctly to the alternator.
Is your starter relay installed and connected correctly? There is a difference between the battery post and starter post. The starter post is wired internally to the small terminal that connects to the ignition system to provide full battery voltage to the coil during cranking. If the battery cable is connected to the starter post of the relay it will be providing battery voltage to the ignition system without the starter relay engaged and will drain your battery. Measure the voltage between the small terminals of the starter relay and battery negative with the ignition off, should be 0 volts....? maybe its too early for me... are you saying there is a post inside the battery? Or, ..hmm..


.....................Is there another relay or
............? ?...........switch here?
...............|.|..............|?
+ ------ = SOL = ------------{starter ?}
...............|
............(G.S.N.S.)

- ------------{ bolt ground engine block }

I just bought the cutoff switch, but it sucks, cause i have to pop the hood every day and night. :

[chrism]

Here is one place to check that you may not have thought of.
On my cherokee the source of this problem was the tailgate window key switch. It was shorting out and slowly draining my battery every night. Finally it stopped working all together and my battery would stay charged.

I bypassed it for the time being and just have the windows wired up to the internal switch.

Just another thing to check.

[Wesdog]

...? maybe its too early for me... are you saying there is a post inside the battery? Or, ..hmm.. :[/qb]I was talking about the starter relay on the passenger fender not the battery. Now maybe there is a difference in the later model FSJs that I don't know about and they don't have a starter relay on the passenger side fender. But assuming they do, there is a connection inside that relay between the starter relay post that connects to the starter cable and the small terminal on the same relay that is labeled 'I' (I think). The wire that connects to that terminal goes to the coil or ignition system. When the ignition switch is turned to start the engine the battery post of the relay is connected to the starter post of the relay to power the starter. This also applies battery voltage to the small 'I' terminal on the relay to provide full battery voltage to the coil to assist in starting the engine. If the starter relay is installed incorrectly by reversing the starter/battery post connections, then that little 'I' terminal will always have battery voltage on it instead of only when starting the engine. That would mean that when the engine is turned off the battery is still connected to the ignition system and that will drain the battery. Does that make sense? Wes

[ March 11, 2003, 08:02 AM: Message edited by: Wesdog ]

[Masato]

Thank you all, you've given me some ideas where to ckeck and explained things I didn't understand, like the #1 and #2 terminals on the Delco alternator and the small terminals on the relay.

You're right about cause and effect Joe, but I don't remember when it started, it was more than 5 alternators ago.

I'll check into all your leads and report back, thanks again.

[mdill]

Yeah,

So far I have had the brake light switch which would turn on after I left the car,
The rear window switch which would do 10+ amps with no indication (I have
no idea yet where the 120 watts were dumped). The passanger vanity mirror
wire broke off the switch the terminal and would turn it on some times, notice
that when I usually drive alone and it is tucked in the up possition, took the kids messing
around one day and viola there is the problem. These can be fun smile.gif

Mike D.

[andy d]

i think i have cured the similar short i had.i think it was either the wires to the dome light shorting in the wet floor, the connectors were in a puddle of green water. or it may have been a hosed up rear t/g switch which i cut out of the circuit just as Chris had done.

[xc_xtc]

Can i get to my T/G switch by taking off the lock by the two Torx srews?

[bigblack'74]

just put a test lite between pos. cable and pos. batery post it will light if there is a draw.. then go pull fuses till the lite goes out..then it isolated to that curciut..which is smiliar to what joe said but that is what we do first..

[andy d]

i dunno, i just grabbed the wires and yanked :eek: the switch came out with the wires. i wasnt concerned with replacing it. i think to do it right, the window has to come out. and then perhaps the sheetmetal cover. i dont think removing the lock and the escutcheon around it will help much. i think it just holds a lever that operates the switch. the switch is just a glorified rocker, very much like the window switches.