I hate Radio Shack! After talking to three morons, concluding with the manager, they told me it is impossible to correct this problem. Here is the story...

I just put a new battery in my car. If I let it sit a couple days, the voltmeter on the dash reads around 11.8 - 11.9 volts, not enough to crank the car over. Anyway, I know something is draining on the battery. I wanted to get a clamp-style ammeter at the battery and see what was drawing by pulling out fuses and checking the meter for a change as I pulled out each one. The manager says the ammeters they sell only work on AC applications. WTF? I wasn't sure, but would checking the amperage going through a wire matter if it was AC or DC? I didn't think so. Oh. The only ammeters they sell read a maximum of 10 amps. WTF? They only had digital today, but I bought one there a few years ago that was analog and would read up to 30 amps.

I then told him I planned on using a voltmeter in the fuse box to check the terminals one by one and see what was going on there. But when I told him there are other things on my car like a stereo system and fog lights and such, he told me the only possible way to determine this was by dissconnecting a wire, any wire, and let it sit for a couple days and see if my battery was drained. If I picked the wrong wire, I would have to one-by-one, do this to every wire on the vehicle until someday, maybe three years down the road, I actually disconnect the right one and find the drain. He said if the draw doesn't go through the fuse box, it is totally impossible to fix. This is the most ridiculous thing I have ever heard.

At that point I was so irritated I walked out to "consult the boards". I did not get an ammeter, but something tells me I should have. I know this will be possibly time consuming to find, but will someone tell me the RIGHT way to find this voltage draw. I think I was on the right track, but I want to know the best way to do this and have the right tools. Thanks in advance.

 

Well I don't know if I'm qualified to speak about this, but I'll give you a little background: I was the asst. mgr. of a test equipment repair and calibration lab for about 5 years in one of my former lives. We were a dealer for (among other brands of meters and such) Amprobe, Sperry, Simpson, Triplett, Weston, GE, Westinghouse, and Fluke. We wouldn't accept a Micronta (Radio Shack) meter for repair because it wasn't real test equipment; their product is like a toy compared to the real thing. Why we didn't apply the same reasoning to Sperry or GE I couldn't figure out.

A typical inexpensive clamp-on ammeter won't measure DC because it is basically a transformer, and as we all know, transformers "ignore" DC. There are DC clamp-on meters made; however they are quite expensive because they are basically magnetometers. They are also not useful at small values of current (less than 10 amps or so) because the magnetic field produced by such a small current is of the same order of magnitude as the earth's magnetic field, and so is swamped by it.

You'll have to use an in-line type of ammeter to find your parasitic drain. You should be able to hook it up in series with your battery, and pull fuses to find where the drain is.

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"So many Mustangs, so little time..."
ICON Motorsports

 

OK. Picked up an inline ammeter that measures up to 20 amps. I hope that is sufficient. Anyway, what type of draw is acceptable (I know it would be minimal)? Sorry, I didn't check what it is now yet, but what do I want it at? Don't head units draw a trickle for memory purposes? I guess what I am asking is what circuits should be drawing when the vehicle is off, and how much should one expect it to be normally?

Thanks for the reply RB, I understand what you are saying about Micronta products. Needless to say, I am not excessively rich nor do I do electrical work everyday (used to to an extent). I know Radio Shack's products are junk compared to some of the others you mentioned, but I had to spend almost $70 on this piece, I'd hate to think of what a quality piece would cost.

 

The average draw of a car sitting is around .2 to .3 amps. Not much at all, that's just memory circuits running. Don't forget to close the door and disconnect the hood light or it will read over 2 amps. I'm sorry you spent $70 on a 30 amp meter, it's overkill for looking at drains. You would have been fine to get a multimeter that measures AC, DC, amps and ohms, that way it's still useful. The amp scale usually goes to 10 amps max if you plug the red lead to the third hole, if the meter doesn't have a third hole look at the data plate on the back for the amp limit.
To read amps in-line disconnect the negitive battery cable and hook it to one of the meter leads, hook the other meter lead to the battery negitive side. It doesn't matter red or black, your reading in-line.

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86 Camaro Sport
383 Speed-O-Motive Crate Engine, Raptor 700R4 Tranmission, Trick Flow Twisted Wedge G2's, 58mm Accel TB, 3.73 Auburn Pro, SLP Cold Air Induction and Headers, Dynomax Cat-back, Serpentine Belt Setup, Dual IROC Fans, Jamex springs, 16" IROC Rims, 36mm/24mm Sway Bars, Global West Steering Brace. Hotchkis Rear LCA's,Panhard Bar and SFC's.
My Camaro Project

 

One more thing, if you do have a drain and it's still there after pulling all the fuses start looking at the in-line stereo fuses or the fusable links under the hood.

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86 Camaro Sport
383 Speed-O-Motive Crate Engine, Raptor 700R4 Tranmission, Trick Flow Twisted Wedge G2's, 58mm Accel TB, 3.73 Auburn Pro, SLP Cold Air Induction and Headers, Dynomax Cat-back, Serpentine Belt Setup, Dual IROC Fans, Jamex springs, 16" IROC Rims, 36mm/24mm Sway Bars, Global West Steering Brace. Hotchkis Rear LCA's,Panhard Bar and SFC's.
My Camaro Project

 

Thanks for the reply. Actually it was pretty much the nicest multimeter they had, 24 range digital and it has a PC interface with software, for what I have no idea, I'll probably never use that. The other 2 models they had were only $10 cheaper and the scales weren't as broad as this ones. I have a couple cheapies (one analog, one digital) but their amperage scales are too small to be doing this. My main concern was being able to read amps on a larger scale than 250mA.

.2 or .3 amps huh? I'll see what I come up with. Thanks again John.

 

you don't need an ammeter. You can do the same thing with a homemade testlight put inline between the battery terminal and battery cable.
First things to start unhooking are the wires at the starter and at the alternator to find where the draw is coming from.

one thing I see wrong is that 10 or 11 volts is plenty to start a car engine. If you are using a new battery and new cables, then there is something either wrong with the starter or your voltmeter.

 

The starter could be a possibility. Or perhaps something else is amiss here. I'm at a loss at the moment.

Here is the scenario when I leave the car sit for a couple of days:
When I turn the key, I get absolutely nothing. Not even clicking. Dash guage reads around 11 volts. But when I hook the jumper cables to another car battery in a vehicle that is not even running, it cranks over with no difficulty.

When the engine is running, ( I have an aftermarket digital dash) the voltmeter reads 14.0 volts, so I'm sure the charging system isn't the problem. With the car off, I checked the battery with my meter and it reads 11.1 volts. It starts fine if it has been run the same day with the same voltage reading on the dash - 11.2 volts. I just bought the battery less than a month ago.

I checked the amperage draw with the ammeter and I get .01-.02 amps.?? (inline on the neg. batt. cable, doors closed, underhood light burnt out) Maybe it's not a draw on the battery. What else is suspect though?

Maybe I got a bum battery? (BTW it's an Autocraft 630/750) I can't see how though. Anyone have any ideas?

Also, the car has been driven about 100 miles in the last two years (one outing to a detail shop last summer, 50 miles there, 50 miles back), although it is started and ran periodically and I did drive it up and down the street last week. Anyway, with replacing the battery a month ago, I know I shouldn't have this problem.



[This message has been edited by 89ragtop (edited May 10, 2001).]

 

I would try again and this time open a door with the meter connected and look for an increase. This is checking to make sure the meter is properly hooked up. The .02 amps sounds too low, SOMETHING should be drawing, at least the stereo memory.



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86 Camaro Sport
383 Speed-O-Motive Crate Engine, Raptor 700R4 Tranmission, Trick Flow Twisted Wedge G2's, 58mm Accel TB, 3.73 Auburn Pro, SLP Cold Air Induction and Headers, Dynomax Cat-back, Serpentine Belt Setup, Dual IROC Fans, Jamex springs, 16" IROC Rims, 36mm/24mm Sway Bars, Global West Steering Brace. Hotchkis Rear LCA's,Panhard Bar and SFC's.
My Camaro Project

 

John, door open with interior lights on, I get .52 amps. It is hooked up right, because I have remote locks and every time I touch the leads so juice moves through the cable it briefly draws 11 amps to flip the locks, and you can hear 'em, and goes back down to .01-.02 amps. So I don't think there is a draw.

 

if you didn't have the problem before the 'new' battery then the battery is bad.
try another one.

 

first off If it's a autocraft battery take it back and have the store check it They have a machine in the store to check for a draw and to check the starting and charging system. Also there could be a bad diode in the Alt. that would allow the guage to show charging but wouldn't be putting amperage back at the battery. And also your best bet as far as checking the way you are doing is to turn your meter to low scale voltage. And see what it show's.

 

I did have problems. My battery was bad. It wouldn't hold a charge due to the fact that is was old and, like I said, in the last two years, it has been diven 100 miles. I did start it about once a month in the winter when it was stored (had the negative battery cable disconnected). In the summer I started it about every two weeks with the battery connected, last summer I had no problems yet. This last winter it finally bit it.

The reason I didn't immediately associate this with maybe a bad battery instead of the voltage draw is because of the little use it gets. I expected the battery to go bad. With the battery unhooked most of the time, and when it is hooked up,having the car not start because it sits so long on an older battery without being charged, I haven't had much of a chance to experience this problem under seemingly normal conditions, like trying to start more frequently to simulate normal use. When I run it, I leave it run for awhile, up to operating temperature. I know that is more than enough time to give the battery a real good charge.

 

How do you test this diode in the alternator? How do you tell if it is bad?

I am going to have the battery checked.

 

First off, the cut off for parasitic draw is 50 milliamps. Secondly, yes, the memory of the radio and a few other circuits draw some current when the car is not running and the ignition is off.

As far as the diode goes, you have to dissassemble the alternator and use the diode checker function of your DVOM. All you have to do is test the leads on the rectifier bridge both ways. If any of the diodes allow current in both directions, than they are bad.

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Matt

1987 GTA L98 MD8 GW6

"Stop Lights timed for 35Mph are also timed for 70Mph"

[This message has been edited by Matt87GTA (edited May 10, 2001).]

 

My mistake, I missed a zero. The draw should be between .02 to .03 amps with a max of .05 amps like Matt said.

Check with your local parts store, most of them have a machine that can test the alternator if you carry it in. Free of charge.


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86 Camaro Sport
383 Speed-O-Motive Crate Engine, Raptor 700R4 Tranmission, Trick Flow Twisted Wedge G2's, 58mm Accel TB, 3.73 Auburn Pro, SLP Cold Air Induction and Headers, Dynomax Cat-back, Serpentine Belt Setup, Dual IROC Fans, Jamex springs, 16" IROC Rims, 36mm/24mm Sway Bars, Global West Steering Brace. Hotchkis Rear LCA's,Panhard Bar and SFC's.
My Camaro Project

 

Thanks for all the help guys. I will take the battery and alternator into today to be tested and will post the findings.

 

I had a similar problem with an import I use to own. Turned out the alternator had a short.....worked fine when running but would kill the battery overnight. Let us know what the results of your alt test are.

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92 Camaro RS, LO3, 5-spd, T-tops

Performance:
K&N Open Air Filter, Edelbrock performer TBI intake, Fastchip Prom, Timing +4 degrees, Centerforce clutch, Xact 8mm wires, SLP 1 3/4" Headers (coated), Flowmaster Catback Exhaust, Z28 Grille w/aftmkt fog lamps
Electronics:
Alpine 8030 Alarm System, Valentine One Radar Detector (How did I ever drive without one?), Pioneer DEH 7450 Head Unit w/6-pack CD changer, Pioneer DEQ 7600 Sound Processor, 2 Kenwood KAC-846 Amps powering 2 12" Pro Red subs, 2 Pioneer 6x9 and 2 MTX 4x6 speakers.
NEXT UP: TBI mods, 3.42 gears w/Torsen posi

 

I have a 85 305 TPI/700R4 in a buddies garage. It is non-serpentine of course, but it's not in front of me to look at. Can I use that alternator just by swapping the pulleys on it? Both connections should be the same, right? Will it mount the same though? Sorry, like I said I can't even look at it until tonight.

I am still taking these parts in to be tested, I just want to know if I have to buy another alternator. I can't test it myself because I don't have those inverted Torx sockets to dismantle it(mind as well buy some of those while I am there). Also, can I simply replace the old parts or do I need a whole new alternator? I rebuilt one with just new bearings because it was squeaky, didn't need any electrical parts. Do auto stores stock these parts? Thanks.

 

I took the battery and alternator in. The alternator tested fine putting out 14.0-14.1 volts. Adequate to see lots of more use. Diodes and stator were good.

The battery I just bought from them a month ago: JUNK. They replaced it and I should be fine.

Again, thanks to all for the assistance.