Batt. drain light test Q

[Shaggin' Wagon]

Fellas - first, I'll admit that I'm ignorant on the multimeter except for spearing martini olives with the probes. I have tried to use a light tester between the neg post and neg cable to find if I do have a drain. It will light dimly for half a second. I've been told that means there is no drain. Battery and alt are both good. This wag is not driven very often and after 2 to 3 weeks it won't start. Should I just keep it on a trickle charger or keep looking for a drain? My other Wag doesn't seem to have this problem. Thanks.

[J4GRAND]

I'll admit that I'm ignorant on the multimeter except for spearing martini olives with the probes And here I thought I was the only one to do that!
Absolut Martini, shaken with 2 bleu cheese-stuffed olives. MMMMMM.

As for testing with the multimeter, place your meter to a low amps setting and place in line with the negative post and cable. If it's reading a few amps, you have an item that is hot and draining the battery.

[Shaggin' Wagon]

Thanks for the reply Patrick. To explore my ignorance with multimeters, I'm assuming you're referring to the DCmA or DC V settings.

[J4GRAND]

I'm trying to picture what settings I have on my multimeter. The DCmA is for milliamps will may be too low; you should have a DC A (DC AMPS) setting that should work.

[Shaggin' Wagon]

That could be my issue. It's a dinky one with DC V settings of 2.5,50,250,1000 and DCmA settings of 10 and 250. Every thing else is AC or OHM.

[BRUTUS]

DCmA is what you want to use. IF and only IF the value climbs and then errors... go to the next setting (DCA I assume). They are scalar to each other so don't worry about anything exploding on you. YOU CAN'T HURT THE MULTIMETER!

You do realize that V is for volts and you will never find a drain measuring volts.

Think of electricity as water. Voltage is equal to water pressure. Amperage is equal to flow rate. Think of your wires as water pipes.

So using this analogy... one of your pipes has a small leak in it.

This is what I would do:
1st test: take the negative terminal off the battery and tap it against the negative post. If there is a spark you have a drain (go to test 2).. no spark=no drain.
2nd test: set multimeter to DCmA, disconnect negative battery terminal from battery, attach red lead of multimeter to negative post of battery and black lead of multimeter to negative cable. The reading on the multimeter will tell you how much is draining.

I will tell you that when I bought Brutus, I had a serious drain on the battery. It turned out that the ignition tumbler in the column was no turning to the "lock" off position. It was staying in accessory and the tach light was draining the battery. These are the tricky ones to find because there isn't really a "test" you can do to find them in most cases. The easy ones to find are when you have a bare wire that looks burned around the insulation because it has worn through the insulation and is grounding out (includes sparking).

I have to say that I am proud of you for even HAVING a multimeter. That is the first step.

[Shaggin' Wagon]

Thanks for all the insight Brutus. I did as you said and and the meter actually went a touch backwards. Sooooooo, if this is correct, I don't have a drain outside of the clock, radio memory, etc. I'll have to go whoop up a martini with said multimeter. Maybe I should take a course and go buy a nice "real" meter. Thanks again!

[Spectre]

No course is needed - you just have a manual range meter, which can be confusing to use. What you're looking for is an autoranging meter, which will figure out what range to use by itself - and therefore has fewer selections on the front panel.

Currently, RadioHack has deserted their customers and offers few decent multimeters (though they have a pocket autoranger that's nice to have in the toolkit for $24).

Here's a good solid, inexpensive meter that includes a contact temperature sensor (good for diagnosing things like coolant temps and catalytic converters):

http://www.sears.com/sr/javasr/produc t.do?BV_UseBVCookie=Yes&vertical=TOOL&pid=03482400000&subcat=Multi-Meters%2C+Testers+%26+Accessories (http://www.sears.com/sr/javasr/product.do?BV_UseBVCookie=Yes&vertical=TOOL&pid=03482400000&subcat=Multi-Meters%2C+Testers+%26+Accessories)

This one is only $30, but is on sale for $20 this week.

[ February 24, 2006, 01:40 PM: Message edited by: Spectre ]

[Shaggin' Wagon]

Thanks Spectre. I'm I'm going to see if my local sears has it before I get it online. I posted something for you over in tech......

[Shaggin' Wagon]

Well.....I thought this issue had magically disappeared. I've somehow jammed my tailgate window in the up position. It will not come down. Now my batt is draining within a day and a half. Obviously, the motor is draining the batt right?. I'm feeling my way around my new multimeter and pulled the neg cable. Tested between the neg cable an neg post and got .94mA. That's fine correct? What the hell is going on?

[BRUTUS]

Well.....I thought this issue had magically disappeared. I've somehow jammed my tailgate window in the up position. It will not come down. Now my batt is draining within a day and a half. Obviously, the motor is draining the batt right?. I'm feeling my way around my new multimeter and pulled the neg cable. Tested between the neg cable an neg post and got .94mA. That's fine correct? What the hell is going on?

Electrical gremlins never "magically disappear" they just hide until the right moment approaches.

1amp = 1000milliamps so 0.94 mA = 0.00094amps which is nothing for a draw. This amp draw certainly doesn't represent the jammed tailgate window. This draw shouldn't be killing your battery. Just make sure it was .94 mA and not 0.94 amps.

How old is the battery? Have you popped the tops off the battery? Is there lead floating in the water (replace battery)? Can you see water in the battery? If you can't see water or the water is low you need to replace the water with distilled water. IIRC the water level should be to the bottom of the inspection tubes (that you are looking through).

To see if the battery is bad... run the engine to charge it up. Shut off the engine and pull the negative battery cable for an extended period of time. When you put the negative terminal back on, see if the truck starts up. If it doesn't, the battery isn't holding a charge.

The other thing you can do if it turns out that it is a circuit is to leave the multimeter on "mA" between the negative battery post and the negative battery cable. Then start pulling fuses one at at time, checking the multimeter with every fuse that you pull out to see when the multimeter goes to zero.

I am pretty sure you don't have a short... otherwise the draw would be bigger. Do you have a clock or a radio that remembers radio stations? Either of those would pull 0.94 mA.

[Shaggin' Wagon]

I should have noted that I'm using a batt charger to get it back up to speed. I'll try the neg cable trick and see if that makes a diff. I've swapped two diff batts in there and they both do the same thing. I'm definate that i'm on mA readings. When I originally posted it was a minor issue over a couple weeks. Now it's nearly immediate. I have another question. The multimeter gives me the same reading whether the hood is up with the light "on" or hood nearly down with it "off". The light tester light ups with the hood up and does an initial flicker then nothing with it down. I hate mechanical science.

[BRUTUS]

I should have noted that I'm using a batt charger to get it back up to speed. I'll try the neg cable trick and see if that makes a diff. I've swapped two diff batts in there and they both do the same thing. I'm definate that i'm on mA readings. When I originally posted it was a minor issue over a couple weeks. Now it's nearly immediate. I have another question. The multimeter gives me the same reading whether the hood is up with the light "on" or hood nearly down with it "off". The light tester light ups with the hood up and does an initial flicker then nothing with it down. I hate mechanical science.

If it takes a charger to get it back up to snuff EVERY time it could be a

bad alternator (parts stores can test)
bad voltage regulator
bad ignition switch (first thing I fixed on my rig 4 years ago) -massive short
bad starter (just fixed this one recently) - have this tested at the parts stores.A test you can do to test the output of the alternator is after the rig has been running for a while, remove the negative battery terminal from the battery. The truck should still run meaning that it is running off the alternator output only... if the truck shuts off, it is running off the battery (this will certainly drain the battery) because the alternator isn't charging the battery.

[Shaggin' Wagon]

The alt certainly isn't doing it's fair share. I've already made the decision to upgrade. losing a full charge after a day or two is killing me. Why isn't a draw showing up? Could I have two bad batts? I've pulled the neg cable so I'll see if just sitting there it will hold a charge. frickin' Jeeps......

[Shaggin' Wagon]

Well, i went out this morn and did the same tests. the multimeter still says .94 mA draw but the light test goes nuts bright unless I pull the tailgate motor relay. I think I'm satisfied that the tailgate motor is the issue. I've hooked the neg cable back up and I'm going to give it a few days without the tailgate motor in play to see if it drains. If it does drain I'll start on that case of vodka.

[shimniok]

I prefer to measure resistance rather than amps. If there's a short, you are going to be running a LOT of amps through the multimeter. It seems like you'd want to start on the high setting to avoid pegging the meter, then selecting lower ranges as needed.

Disconnect the - and + battery cable, then measure resistance in ohms across both. You can figure out amps by dividing 12 by resistance. (V = IR so I = V/R)

You can start pulling fuses and breakers until you find the circuit the short is on. I've got short that comes and goes in mine that I think is the tailgate.

I don't even know if my Fluke 73 will handle massive current. It has two inputs, one fused to 10A the other I think is unfused but not sure what the limit is.

Michael

[drlocke]

The various responses to the query about use of a VOM as a current-measuring device are a bit cloudy about specifics. It IS possible to destroy a milliameter in doing the "drain test" where the battery cable is disconnected and the meter run between the cable end and the battery post!!!! :eek: Keep that in mind! This applies to the old-fashioned d'Arsonval (needle) type meters where the current or voltage range has to be manually selected. Use the amperage ranges for measuring current draw, and use the voltage range settings for measuring voltage from source to ground. Use the wrong setting by underestimating whatever possible current you may encounter and you will overdeflect the meter and curl the needle, ruining the calibration. The better VOMs have fuse protection, but many of the cheaper ones don't, so when the mistake is made....Poof!

An autoranging DVM is a better bet for today's novice, so Spectre is right on that count. Ratty-Old-Shack or Swears--either or is probably as OK as the other. :rolleyes: Or you can go to a reputable supplier and buy a Fluke if you want to spend some dinero. Whichever meter you get, READ the user manual as raptly as you would your favorite novel, and heed the directions to the letter.

But that aside I usually use one of those awl-style test lamps, where you usually attach the alligator lead coming off the handle to a ground and then probe for sources of power and the handle lights up nicely when +12 volts is encountered. But in the drain-testing pull the negative battery cable and attach alligator clip to its bolt, and the prod stab into the negative battery post. The filament lights dimly in newer model cars and not at all in older ones if everything is normal.

Usually a case of battery run-down in disuse can be traced to sedimentation in the battery shorting out the bottom ends of the electrodes in one or more of the individual 2 volt cells.

[Gambler68]

Well, i went out this morn and did the same tests. the multimeter still says .94 mA draw but the light test goes nuts bright unless I pull the tailgate motor relay. I think I'm satisfied that the tailgate motor is the issue. I've hooked the neg cable back up and I'm going to give it a few days without the tailgate motor in play to see if it drains. If it does drain I'll start on that case of vodka.

if your tg motor is drawing, you can tell because the wires in the tailgate will be HOT, or at least very warm. If you look under your rear bumper up in the drivers side quarter, there is a brown/tan quick release plug you can pull apart to disable it (at least on my 79 there is).

[Golddust]

I had this same discharging problem for about many years. Finally bought a new battery and still had the problem. The old 77 should have no draw when key is off except the for the clock. I used a VOM on volts between the neg terminal and the neg cable. Showed 13.5 volts with battery charged. This means a complete circuit is made with some device, ie clock, lights etc. I knew the clock could be drawing even tough it needs to be hit, pound on dash for it to work. I disconnected the clock at the fuse box. Volts went to zero and the battery does not discharge anymore. After four or five weeks the 360 turns over and I don't even have to prime the carb anymore.

[BRUTUS]

The alt certainly isn't doing it's fair share. I've already made the decision to upgrade. losing a full charge after a day or two is killing me. Why isn't a draw showing up? Could I have two bad batts? I've pulled the neg cable so I'll see if just sitting there it will hold a charge. frickin' Jeeps......

I am thinking that the draw isn't showing up because RUNNING the jeep is causing the battery to drain... then when you shut it off, the battery is already dead (either because it won't take a charge from the alternator when it is running or the battery is just bad).

I have gone through this problem a few times

1) When I first bought the truck, the PO told me that "every time I shut the truck off, I need to disconnect the negative battery terminal". The ignition tumbler would not go to the "off" position. So I bought a new tumbler and replaced it and that turned out to fix the draw on the battery as luck would have it.

2) The second time this appeared is right after I put my first electric fan on and the alternator couldn't keep up and killed itself. Bigger alternator (110amp) fixed this problem.

3) A few weeks ago, my starter was going bad (tested fine at parts store), still turned the motor over, gear was engaging and disengaging fine. My only hint that it was going bad is that the starter alone would drain a very capable charged battery in a matter of seconds. It was only after I listened to my roomate start his Chevelle for what seemed like 5 minutes of continuous hard cranking on a 12:1 compression motor that convinced me that the starter wasn't using all the electricity it got to start the motor.

Since you have gone through two batteries already, I don't think the battery is the cause.

Did you already try to run the motor with the negative cable disconnected?

[yankeedog]

yup you can destoy a multimeter touch one post to battery positive and one to battery negative while in ANY amp range with an old school cheapo analog meter and watch it go snap crackle pop while it tries to read INFINITE amperage.there will always be some drain.radio ,clock, that kind of stuff.and eletrical gremlins NEVER go away they are like rust they might sleep for a while.but they are always there until removed.Currently though I am working exorcism software to replace the current chants and incantations i am using now.

[Shaggin' Wagon]

I did not try to run the engine with the neg cable off. I left it off overnight and it fired up with no prob. I've taken it to my body shop guy to get the tailgate motor issue worked out. I just don't have time to tear into that with the races next weekend. I'm hoping that I can kill two birds with one stone. If I get back and still have the draw I'm back to square one. Thanks again for all of the input.

[BRUTUS]

I did not try to run the engine with the neg cable off. I left it off overnight and it fired up with no prob. I've taken it to my body shop guy to get the tailgate motor issue worked out. I just don't have time to tear into that with the races next weekend. I'm hoping that I can kill two birds with one stone. If I get back and still have the draw I'm back to square one. Thanks again for all of the input.

It sounds like you are on the trail to the solution. The battery/starter/alternator sound like they are fine.

Why did you take it to a bodyshop guy to fix the tailgate motor? Is he a friend of yours? If you don't have time to tear into it, disconnect it until you have time.

[Shaggin' Wagon]

It sounds like you are on the trail to the solution. The battery/starter/alternator sound like they are fine.

Why did you take it to a bodyshop guy to fix the tailgate motor? Is he a friend of yours? If you don't have time to tear into it, disconnect it until you have time.
Well, it's not that simple. The Carolina Cup is next weekend and I have to stick 4 large coolers of beer and assorted goodies back there.:D You know.....priorities......:thumbsup:

[BRUTUS]

Well, it's not that simple. The Carolina Cup is next weekend and I have to stick 4 large coolers of beer and assorted goodies back there.:D You know.....priorities......:thumbsup:

Get a J-truck... with a brow! :D

[Shaggin' Wagon]

Get a J-truck... with a brow! :D

I'd love one. Saw one today that looked like it was about to break in half.:eek: