Electrical Question...

[MattORourke]

I recently moved back down to TX from NC and drove my mustang the whole way. The car did great considering it's hardly been driven in the past three years, but around the last two hours of the trip I noticed the battery gauge dropping. Eventually it got the the point where if I would turn on my blinker, my stereo would cut out. Literally, as soon as I pulled into the driveway of my new house, the car died. I tried to jump it, but no dice. I looked at my records and realized that the battery was old so I got a new one. Put it in, car starts great - yippee. A few days pass and I go to start the car again - dead as a door nail. The brand new battery, though, will take a charge, so I got it recharged. I finally got around to hooking it back up this morning and it started just fine. went for a drive - battery gauge held steady between the M and the A, actually went up a bit towards the A. so i did some research in the forums here and did a few things:

1) tested charging system - with the car running the volts read around 12.4, which i know is low but that doesn't explain my problem of the battery draining.

2) I checked as many grounds as I could find, they all seemed good. I also looked inside the vehicle to see if anything was not turning off and consequently draining the battery - again nothing.

3) I went through the process of pulling all the fuses to see if i could figure out where a battery drain might be located with the car off. basically, nothing came from this. there was very little change in current, which stayed around -5.3, although it seems to me that -5.3 is not good.

So I guess the question here is - where do I go next? I do have an alarm system installed, but it's been there for years and has never caused the battery to drain. when i rev the engine, the battery gauge goes up a little bit, but stays around 12.2 V at idle. Also, when I turn the power on, not the ignition, my battery light does not come on. I remembered reading something about this in a previous thread saying that meant my charging system was not engaging. that may be true, but the gauge went up as i drove?! either way, that doesn't explain why my battery would be dead after starting the car once, shutting it off, and having it sit for a couple of days.

any help is greatly appreciated. I'm not the most mechanically inclined person, so any answers in english are more greatly appreciated. thanks

cheers,

Matt

 

[jrichker]

if the alt doesn't put out at least 13.2 volts, the battery won't charge. Fix your charging problems and then look for current drains.

5.2 is a number, no more and no less: it is useless without knowing if it was volts, amps, milliamps or microamps. Many modern DVM auto range, so you have to look carefully to see what the number represents.

 

[HISSIN50]

Jrichker is right-on.

FWIW, the parts store can do a dynamic testing of the charging system - that might be a place to start.

Good luck.

 

[MattORourke]

Thanks for the help. So you guys are saying I need to replace the alternator and then try and find the drain, if there is one. Am i wrong to think that something is draining the battery? it doesn't seem to me that a brand new battery should die after starting the car once and then sitting for a couple of days, right?

I believe the -5.3 was Amps.

HISSIN50 - this may seem like a silly question, but i have literally been living in the woods for the past three years, but what does FWIW mean?

also, i did go to the parts store for the testing and all the guy could say was, "well, looks a little low. you might need a new alternator." that's about all i could get from the guy, then he went back inside to deal with all the other customers and left me to play with his machine.

anyway, I'll look at replacing the alternator and any advice you might have for finding the drain on the battery would be appreciated. thanks again.

cheers,

Matt

 

[FrumRoll]

If you remove the alternator from the car, many parts stores can test that alone.

 

[HISSIN50]

FWIW = For Warriors In the Woods..............

Ok actually it's: For What It's Worth.


I would definately troubleshoot a bit more before tossing parts at things. That can get right expensive.

Your battery light thing is a little weird. I would have said bad regulator, but you noted the voltmeter moves a little with alternator speed changes. I still would not rule it out. If your battery light never comes on, the idiot light bulb might be burned out. There's a resistor in parallel with the bulb to keep the circuit functional (if that circuit is dead, the alt is dead).

You can definately have the components bench tested - just note that bad wiring is not taken into account. I would want to test the readings at the regulator plug and ensure that the fusible links for the alt are in good shape.

Jrichker and the other smart folks will have some good insight for you.

Good luck.

 

[MattORourke]

Honestly, I like For Warriors In the Woods better...

alright, so remove the alternator and have that tested - no problem, i can do that tomorrow.

the problem i still see here, though, is that none of this seems to be addressing my original problem. namely, the brand new battery i installed lost it's charge after sitting for a few days, not driving. it seems that looking at my charging problem might be something i need to do, but should it be done first; does it have to be done first?

granted, this all began when my battery lost it's charge while driving, but after testing that battery and attempting to re-charge it, the battery itself wouldn't hold a charge - it was 5 years old. all the "evidence" that i've seen says that maybe my system is running a little low, but i'm not losing a charge while driving, it's only when the vehicle sits (not running) and the battery is hooked up that my charge drops. am i wrong?

again, thanks for all the help, i do appreciate it.

cheers,

Matt

 

[HISSIN50]

Matt, at best 12.4 volts isnt charging the battery back up, but barely breaking even or slightly discharging it. Each cell in a conventional cell battery holds 2.1 volts, which equates to 12.6 volts. So you need to have 12.6 volts reading on your meter just to break even - less is discharging and more is charging. JR is absolutely spot on that any alternator should put out over 13 volts (I can read over 14 volts just after starting).

We were a little hinky on the current draw issue. If you really have 5 amps of static draw, that's big. Most installers dont like to see more than about 250 mA period (0.25 amps).

Jrichker has a nifty post about checking for circuit draw as I recall. It seems like you've done a bit of that already. Amongst items to check are: sunvisor lights, glovebox lights, trunk lights, all fused circuits (pull the fuses and watch the draw), removing fusible links and seeing if the reading changes, removing the alternator charge cable to see if a diode went south in the alternator, etc. The alternator might be one to check sooner than later, as this can allow a decent sized draw.

Based upon what you've stated, it seems like the issue is two-fold. There is a draw of sorts - perhaps the car was started frequently enough in the past to recharge the battery back up, but now the alternator is taking a poop and cant assist like it used to.
And something still seems to be up in the chargin system - you are really not replenishing while driving (and perhaps discharging). Then the draw that occurs while the car sits is taking its toll.

My two cents. Good luck Matt.

 

[MattORourke]

Again, thanks for all the help, it's been great. I'm certainly not the type of person that can diagnose vehicle problems on my own, and I've never really done any of the work on my own, except changing the oil. anyway, i decided to try to solve this problem without the help of an over-priced mechanic and really appreciate all the input from others.

so, an update... I took of the alternator and regulator this morning and took them to the parts store for testing - they failed. got some new parts, came home and put them on. Viola! the battery light now turns on when i turn on the power and off when i start the car up. I went for a drive - the gauge was definitely much higher than it had been. I turned on every electric device i could think of and experienced no negatives. so, it appears that the charging problem is solved...

part two - the drain. I guess it's possible that this doesn't exist and the problems were a result of my faulty charging system. I haven't made it back to the parts store to check and see if there is still a draw on the battery, but i guess if i go to start the vehicle later and it's dead, i'll know it's still there. assuming it is still there - where do i go from here?

cheers,

Matt

 

[HISSIN50]

part two - the drain. I guess it's possible that this doesn't exist and the problems were a result of my faulty charging system. I haven't made it back to the parts store to check and see if there is still a draw on the battery, but i guess if i go to start the vehicle later and it's dead, i'll know it's still there. assuming it is still there - where do i go from here?

cheers,

Matt

Matt, keep in mind that the alt could have been the source of the drain.

I'd still test the circuits as suggested before - hook up your meter in series with a battery cable and terminal and note the draw (make sure as much stuff on the car as you can turn off, is off). Then start pulling fuses one by one till the reading goes down. You can also pull wires off the solenoid one by one and so on till you remove the device that is creating the draw (and the meter reading goes way down).

Glad to hear that things are starting to come around. If you use a lot of electrical accessories, a 3G alternator upgrade might have been worthwhile.

Good luck Matt.