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-   -   Battery Draining But Parasitic Draw and Alternator Test OK (https://forums.corral.net/forums/electrical-wiring/2489858-battery-draining-but-parasitic-draw-alternator-test-ok.html)

Imatk 04-18-2019 08:36 PM

Battery Draining But Parasitic Draw and Alternator Test OK
 
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!

indy2000 04-19-2019 08:40 AM

what brand battery

tjm73 04-19-2019 10:17 AM

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.

Imatk 04-19-2019 10:46 AM

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.

indy2000 04-19-2019 12:01 PM

YOU have checked current draw on all circuits?

Vanity mirror?

Can drain the battery quickly for example

TomV 04-19-2019 01:05 PM

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.

Imatk 04-19-2019 02:13 PM

Quote:

Originally Posted by indy2000 (Post 18550822)
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?

indy2000 04-19-2019 04:02 PM

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

BlackBeauty 04-19-2019 05:26 PM

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.

AtomicCoupe 04-19-2019 05:29 PM

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.

Imatk 04-19-2019 08:04 PM

Quote:

Originally Posted by indy2000 (Post 18550860)
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.

Imatk 04-19-2019 08:05 PM

Quote:

Originally Posted by BlackBeauty (Post 18550874)
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.

Correct.

Ilusivefox 04-19-2019 08:26 PM

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

AtomicCoupe 04-19-2019 09:12 PM

You’ve never had a NorthStar I bet...

indy2000 04-20-2019 08:44 AM

Quote:

Originally Posted by Imatk (Post 18550936)
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.

tjm73 04-20-2019 11:45 AM

Interstate is good and I've had good luck with Deka. Deka was US made last I knew. In PA I think.

EDIT:
Yes made in the USA and yes made in PA.

http://www.eastpennmanufacturing.com...ns/automotive/

jamessr23 04-21-2019 07:30 AM

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...

indy2000 04-21-2019 09:40 AM

Quote:

Originally Posted by jamessr23 (Post 18551350)
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

Imatk 04-21-2019 10:38 AM

Quote:

Originally Posted by jamessr23 (Post 18551350)
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.

Imatk 04-21-2019 11:05 AM

Quote:

Originally Posted by indy2000 (Post 18551162)
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?

Imatk 04-21-2019 11:06 AM

Quote:

Originally Posted by indy2000 (Post 18551378)
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

Correct.

indy2000 04-21-2019 11:56 AM

my motorcraft 95 rc, reserve capacity rating

95/2.4 = ~40 amp hours

therefore 0.027amp draw is 40/0.027= 1481 hours at that current draw or 61 days

I think your measured parasitic draw is too low to be a problem, battery or charging system is where i would be looking

if you have a DC clamp meter you could compare alt current production and compare it to your system draw, and see if you are at a deficit

I have a 130amp alt, and it can only put a max of, from memory, 65-70amps at idle when i measured

Imatk 04-22-2019 11:12 AM

Quote:

Originally Posted by indy2000 (Post 18551444)
my motorcraft 95 rc, reserve capacity rating

95/2.4 = ~40 amp hours

therefore 0.027amp draw is 40/0.027= 1481 hours at that current draw or 61 days

I think your measured parasitic draw is too low to be a problem, battery or charging system is where i would be looking

if you have a DC clamp meter you could compare alt current production and compare it to your system draw, and see if you are at a deficit

I have a 130amp alt, and it can only put a max of, from memory, 65-70amps at idle when i measured

I measured the voltage drop on starting the car and it didn't drop below 10 and the alt is charging at 14.4 or so... I'm thinking it's some kind of weird intermittent thing.

A wire that's shorting but only occasionally.

Friggin electrical gremlins drive me nuts.

I've pulled the fuses from the car alarm. Going to drive it a couple weeks and keep monitoring and see if that might be the culprit.

indy2000 04-22-2019 11:35 AM

does your battery light in the dash work?

does it ever come on while driving?

do you have a big stereo, electric fan, drive with the blower on high speed?

these loads, can easily put a battery into deficit as the alt cant keep up at idle.

Blown88GT 04-24-2019 08:08 PM

Quote:

Originally Posted by tjm73 (Post 18551188)
Interstate is good and I've had good luck with Deka. Deka was US made last I knew. In PA I think.

EDIT:
Yes made in the USA and yes made in PA.

East Penn Manufacturing | Automotive batteries

Correct.
AAA batteries are Deka with a 3 year full replacement warranty.

Flade 05-01-2019 05:04 PM

I would look for a relay going bad. They can stick closed causing a high drain. It is often intermittent making it hard to find.


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