Need help....Possible Wiring problem

865.0 · Feb 17, 2007

A few weeks ago, my car all of a sudden died while in the parking lot of a local Discount Auto Parts. It appeared to be a dead battery.

Luckily for me, I purchased a new battery and off I went. I checked the alternator to see if it was charging, it wasn't. So, I purchased a new alternator. Everything fixed....(Verified that the new alternator was charging)

Not quite, today the car went dead again. Dead battery. Without any option, having to fix the situation immediately I purchased another new battery. The car started right up and has performed flawlessly all day.

Any suggestions on what to look for that might be killing my batteries. Both, alternator, cables, and batteries are new. I purchased a new solenoid but haven't installed it yet.

Thanks in advance!

87muscle · Feb 17, 2007

first question? do you have underdrive pulleys on your ride cause if you do the stock altenator wont charge your battery very well and its worse if your sitting at idle.also, check your block ground to the starter relay you might just have bad wiring.

HISSIN50 · Feb 18, 2007

If a battery and alt are of known good condition, in your situation I would consider an accessory draw. As the car sits, the item (a glovebox light, trunk light, etc) stays energized, draining the battery off overnight.

You can use your DMM in-series with the battery cable and battery post and measure current draw. Check the instructions with your meter to configure the setting and lead terminal position.

Good luck.

865.0 · Feb 18, 2007

I have a underdrive pulley on my alternator, however it's been on the car for seven or eight years now with no problems. Plus, I checked it at idle and was charging like crazy with the new alternator.

I was thinking the same about some type of drain as mentioned. One key note: Just before my last battery failed, my AC would not turn on, the blower would, but not the compressor. After the new battery and alternator, my AC started to work fine again.
Take two:
Yesterday, after changing the battery out, the AC would not turn on again.
Another note: The Radio turned off on it's own just before my wife parked the car, when I attempted to re-start the radio went crazy, making an usual noise, so I quickly pulled off the face plate to get it to stop. This was all before the last new battery.

Thanks for the advice, I will check different sources with the DMM to hopefully pinpoint the culprit.

865.0 · Feb 19, 2007

Update...

I tested the alternator via the battery with a voltmeter. It's not charging, only managing maybe 12 volts. No difference with the engine running or not.

Another point to add...

With the ignition switch closed, I get 12v at the alternator (two wires going in) and when I open the switch volts goes to "0."

The car managed to stay running for atleast two weeks before dieing again. Couldn't have managed to stay running that long just off a new battery, or could it?

Could it be a disfunctional alternator from Advance Auto Parts?

HISSIN50 · Feb 19, 2007

865.0 said:
With the ignition switch closed, I get 12v at the alternator (two wires going in) and when I open the switch volts goes to "0."

The car managed to stay running for atleast two weeks before dieing again. Couldn't have managed to stay running that long just off a new battery, or could it?

Could it be a disfunctional alternator from Advance Auto Parts?

That is not normal IMHO regarding the charge cables showing 0 volts with the car off (they should float at battery voltage).

I suppose it's possible that you lost a diode and the alt gets by at lower loads but once you load it up, it can't keep up. The battery would be depleted more slowly than with no charge input.

Good luck.

superhuaman · Feb 19, 2007

HISSIN50 said:
That is not normal IMHO regarding the charge cables showing 0 volts with the car off (they should float at battery voltage).

I suppose it's possible that you lost a diode and the alt gets by at lower loads but once you load it up, it can't keep up. The battery would be depleted more slowly than with no charge input.

Good luck.

that sounds like a common problem with parts store alternators

grizzlywilds · Feb 20, 2007

Just so you know. I'm having the same problem I think. But my battery is being drained with the ignition turned off. And the alternater, which checks out good, can't keep up with it.

And to answer one of your questions: YES a new battery can keep your car running that long. It did mine.

Sorry I'm not any help here but I'm hoping someone will find that this is more common and give us an answer. Most likely it's something that will make us look really stupid. I'm hoping it's somethin' stupid easy.

865.0 · Feb 20, 2007

Okay,

I pulled off the alternator, took it back to discount for another one.

Installed it this afternoon, IT'S CHARGING!!!!!!!!!

Let's see how long this one lasts, or if there is another problems that maybe killing the alternator's/batteries.

The last one started off charging as well, I just didn't recognize when it quit.

Getting good at swapping alternators, a little more challenging since it's at the bottom of the supercharger bracket.

HISSIN50 · Feb 20, 2007

grizzlywilds said:
Just so you know. I'm having the same problem I think. But my battery is being drained with the ignition turned off. And the alternater, which checks out good, can't keep up with it.

And to answer one of your questions: YES a new battery can keep your car running that long. It did mine.

Sorry I'm not any help here but I'm hoping someone will find that this is more common and give us an answer. Most likely it's something that will make us look really stupid. I'm hoping it's somethin' stupid easy.

All modern computerized cars have a draw when the car is off. The degree of an unusual parasitic draw, battery condition and frequency the car is driven all play into how long it will take to deplete the battery to the point that it cannot turn the motor over.

I don't like to see more than 200 mA of draw with the car off.

Good luck hunting down your short.

superhuaman · Feb 20, 2007

they taught us in school no more than 50-80 mA...after 30-45 minutes and all the modules have had time to shut down.

HISSIN50 · Feb 20, 2007

superhuaman said:
they taught us in school no more than 50-80 mA...after 30-45 minutes and all the modules have had time to shut down.

Some of the specs on the newer high-end cars with tons of gizmos are in the 150-250mA range.

grizzlywilds · Feb 21, 2007

It's not a new car. It's a 1990 Mustang gt 5.0 that I have.

superhuaman · Feb 21, 2007

yep so...only things there are the engine computer and the radio, the latter taking more power. so i guess 50-80mA is good i dont know what mine is, but my alpine wont drain the battery. it seems some of the cheaper cd players will have more drain (road gear, pyle, dual, lanzar, etc.) not speaking from experience though. if you have the factory radio, then you have something wrong.

possible list of drains...
glove box light <1A
trunk light ~1A
hood light ~1A
interior light ~1A
radio <1A
engine computer (rare) ???
alternator regulator (if damaged) 3-4A

hopefully you dont have a drain though...maybe it was just the alternator not keeping your battery up.

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