No luck finding a battery drain w/ a multimeter
 

I am pretty sure I have a slow battery drain, as the battery retains more voltage longer when sitting pretty and disconnected than when plugged into the car. I lose about 0.5V overnight when plugged in...after a week, no start, obviously... I suspect stuff I did recently (gauges, Voltage reg) but that's not the issue (yet)... I followed common directions:

Set Multimeter to Amps, disconnect Neg cable from battery and run the Multimeter in series between the neg battery post and (-) cable (or do it all on the + side, same thing, just riskier). Observe Amps draw, and start pulling fuses until it the load drops, you've found your problem circuit... Easy in theory... There's even Youtube videos on this for Pete's sake...

Well my Multimeter reads a big fat 0.00, in Amps, milliamps, you name it. Never moves. I've got the leads in the right connectors per the MM screen itself... A low number, I can believe, but 0.00 seems like a wrong read to me ?

The MM is still fused and not broken as far as I can tell. It reads voltage and other stuff fine, fuses aren't melted... I went to an auto store to buy another one, but held off as really good ones are not cheap. The sales guy asked why I needed 2, I explained and he told me regular MMs were "useless" to do this... I needed either a load tester or a quality $$$ Fluke MM. I have seen several Youtube vids on this procedure with what appears to be crappier than mine "run of the mill" MMs... So what am I doing wrong ? Thanks !!

Greg
Are you sure the leads are connected correctly to the VOM?
I have to relocate them when measuring amps such as you're trying to do vs measuring volts or ohms.

Sounds like you may have your meter backwards. Not all read negative.

As sure as I can be... The MM itself lights up the connections required based on my selection - Amps here - and I follow the on screen recommendation :-)

I wonder what other simple test I can do to rule out the MM.

Edit: Pretty sure I tried backwards too, but will try again...

Have you tried to activate some accessories with the tester hooked up to verify it works? Your battery draining problem might be so small that your meter can't read it. I bought a parasitic draw test tool from Snap-on that hooks into a regular multi meter to read very small amounts of current.

-Rutager

...I wonder what other simple test I can do to rule out the MM.


Try your meter using a cheap extension cord and a low watts house lamp.

Cut one wire on the extension cord, connect the MM in series with the cut ends (on the highest Amp range), plug the light at one end, plug the extension cord in the house outlet and turn on the light.

If the light turn on, you will have a reading on the MM.

try the positive leads

It sounds like my meter is shot on the Amps circuit. No accessories power if the meter is in between the battery and cable. Nothing... Maybe the fuses are blown, even though they look ok. Ironically my meter is also a continuity tester but I can't use it on itself :-) I'll go buy another - Just wanted to check that this should work, versus what sales guy told me. Sounds like I'm doing it right, with defective equipment...

No fix for the multimeter, but a common drain (happened to me) is the door-triggered light switch. Sometimes the rubber gets old and the switch gets sticky. There are a few threads about it. Solved my drain problem believe it or not.

81 911SC

Battery drain tests........
 

Greg,

Before you go crazy looking for the cause of your battery drain do these simple tests.
1). Have the battery tested and analyzed. Your local auto supply would do it for FREE. If the battery passes the test with good results, allow the it to sit for a day or two without any load and measure the voltage drop. A fully charged battery would have 12.5 - 12.6 volts. Yours might read less. Measure the initial voltage at day 1 and continue to observe the voltage the following day or 2.
2). If the battery is still fully charged after 48 hours, then continue to investigate for the drain. There is no point to investigate for the power drain if the battery does not hold power without load for a day or 2. How old is your battery? Keep us posted.

Tony

You can also just use a test light connected between the terminal and the battery. If the light is on you have a draw pull fuses until it goes out and that is the draw. Much easier than a MM

Still have the quartz clock? Then you have a (relatively) massive drain cranking away 24/7. I think that they start drawing more power as they age. disconnect it and see if you find your weekly drain is gone.

Most likely the fuse in your MM is for the amp portion of the meter. You can use the DC voltage setting much like like Mike80911 suggested w/a test light. Hook up you MM in series between the Bat neg and its cable. If the polarity is wrong just switch the leads from Bat to cable and visa verca. The problem with using a test light in this fashion is it will not pick up smaller draws to activate the bulb in your test light. You can use the test light to check the amp portion of your MM. Just hook up the amp portion and the test light in series between the Bat and its cable either pos or neg. I never use the amp portion and almost always use the voltage drop method by using the DC volts method and described above. Good Luck
Gary Siemion

I bought a clamp-around milliampmeter for a little over $100-works great-you do not have to disconnect anything, and you can check individual wires for current draw.

^^^this.

I used a DC clamp-on ammeter to troubleshoot a current drain on my 964. It's great because you don't break the circuit to do your testing, which may lead to the offending circuit being disconnected (i.e., reset) until the next time it's activated.

Sears sells the DC clamp-on ammeters.

thats how i did it and everyone that i worked with did it when i did auto electric work for a living.

the MM is fused. if you blow the fuse, it will not work. another reason we used test lights. MM were too expensive to use all the time, not to mention combersome.

make sure the scale you have selected is not too hi for the current draw. if you have it set to "A" and not "mA", you will likely read "0".

Mike80911 has the best and easiest way to test. How old is the battery can have a bad cell. I bought a new battery last year with exact issues you have. Took it back and they tested it and test showed good. Car wouldn't start after a few days. Returned battery and demanded a new one and have not had a issue since. Batteries are not made like they used to be, last four to five years at most albeit the interstate I replaced was ten when it gave in
Ernie 81sc

Had the battery tested and it's fine. So I gave in and bought a cheapie MM to double check. Guess what ? Both fuses on my good MM were fried despite looking great ! The cheapie unit shows a 48 miliAmps drain. Now I can start trouble shooting ! (And searching for those fuses, good luck to me).

Is it ok to leave the MM connected between battery and cable for a few minutes while popping fuses or is it a 10 seconds thing ? Don't wanna fry both!

Battery drain.......
 

Greg,

Using the milliamperes setting is the right way. I have three (3) MM, a Fluke, Sear, and HF (free sample). They all work for tracing this power drain in the car battery. Anything less than a 100 mA is desirable. One thing I learned from this experienced auto electrician was how to connect the MM for the said test. The MM was initially connected parallel connection before the negative cable is disconnected to form a series connection. I was skeptical at first at this method. The electrician was highly recommended by a reputable shop as one of the best in the area. I was able to locate the circuit and fix the problem.

Tony

Greg
When Bob Ashlock and I diagnosed my draw, we just left the MM connected and pulled/replaced the fuses until we found the problem circuit.