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Discussion Starter #1
Having some kind of weird issue with my '91 GT.

The battery will die after about two weeks.

The alternator is brand new and charging at 14.4

Checked the alt with a diode test, checked out perfect... no reading when positive lead was on power post and negative lead was on casing. Reading of .87 when reversed with positive on the casing and negative on the power post.

Checked for parasitic draw and got a reading of .02 amps (or 20 milliamps) which is well within range.

I did test the draw by turning on the car alarm and with the alarm active it stayed at around .027 amps BUT when the alarm was turned off it jumped up to .078 and stayed there.

What am I missing here?

If anyone has any suggestions I'd love to hear them.

Thanks for any help!
 

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How old is this battery? I had a battery that was fine if it was charged. Everything seemed good. But you had one shot at starting because if it cranked more than 5 or 6 seconds it would barely turn over on the next attempt. If it was fully charged and sat for 24 hours, it would barely turn over.

Bad battery. Might not be the problem. But don't ignore the possibility.
 

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Discussion Starter #4
It's a fairly new battery, an "Autocraft Silver"

Battery tests out fine, drops to 10v at startup which is within spec. I suppose I could get a bigger battery, more CCA... I'm beginning to wonder if it's some kind of draw from the alarm.

The alarm has been on the car since it was new in '91 so I'm wondering if it's got some internal issues.

With the draw test when the alarm was active it stayed within range at 30 milliamps, but when it was turned off it jumped up to 80 milliamps and then after 30 seconds or so, went back down to 20 ish milliamps.

That might be because the lights momentarily turn on with the alarm, but I'm not certain.
 

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YOU have checked current draw on all circuits?

Vanity mirror?

Can drain the battery quickly for example
 

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I had a problem like that once, when my Autometer Monster Tach was wired to a constant 12V+. Changing to a switched 12V+ solved that issue. So make sure you don't have something aftermarket drawing on the battery when the car isn't running.
 

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Discussion Starter #7
YOU have checked current draw on all circuits?

Vanity mirror?

Can drain the battery quickly for example
I'm not sure what you mean by "checked current draw on all circuits."

I did a parasitic draw test from the battery and the reading was within spec at 27 milliamps so that would be testing all circuits since there's no other power source on the car aside from the battery.

If the vanity mirror was causing a draw that was more than 27 milliamps it would have shown wouldn't it?
 

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that is correct

if your battery is draining from 27 mA then batt is not good

so are you 100% there is only a 27mA if so then batt is dead
 

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You removed the negative cable and put your Voltmeter between cable and negative battery post? And measured and if high start pulling fuses to see when it goes down? Just curious how you are testing.
 

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Batteries are tough. I’ve had ones test just fine and only actually swapping a new battery fixed the issue. I probably didn’t load test it correctly, but hey....

On the flip side, if you buy a new battery, look at NorthStar battery’s. Made in USA and are as good as it gets.
 

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Discussion Starter #11
that is correct

if your battery is draining from 27 mA then batt is not good

so are you 100% there is only a 27mA if so then batt is dead
I don't even know if you really know what you're talking about here.

I did a parasitic draw test on the car. The draw was 27 mA.

The battery is measured in volts not amps or milliamps so I don't even know what you're saying.
 

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Change to an Interstate battery. By far the best batteries I've ever had. The problem is probably the autocraft silver battery.
 

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You’ve never had a NorthStar I bet...
 

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I don't even know if you really know what you're talking about here.

I did a parasitic draw test on the car. The draw was 27 mA.

The battery is measured in volts not amps or milliamps so I don't even know what you're saying.
oh my........:surprise:

take a step back, read the battery label

then ask yourself why battery voltage goes down while you place a load on it.
 

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I am throwing a hail mary on easter here...but when you say you did a parasitic draw test....did you use the meter and pull each fuse one by one? Just want to make sure a step wasn't overlooked...
 

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I am throwing a hail mary on easter here...but when you say you did a parasitic draw test....did you use the meter and pull each fuse one by one? Just want to make sure a step wasn't overlooked...
i'll assume the poster removed a battery connection, and placed a ammeter in series with it

therefore did a total load/current draw for the car
 

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Discussion Starter #19
I am throwing a hail mary on easter here...but when you say you did a parasitic draw test....did you use the meter and pull each fuse one by one? Just want to make sure a step wasn't overlooked...
I did the draw test, but didn't need to pull any fuses since the draw was well below a "normal" reading of 50 milliamps.
 

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Discussion Starter #20
oh my........:surprise:

take a step back, read the battery label

then ask yourself why battery voltage goes down while you place a load on it.
Ok I understand what you're saying now... I think. You're saying that if the draw is only 27 mA then the battery is bad because it shouldn't be going dead at that low of a draw?
 
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