Someone please help me to read my current (amp) drawn

[rnln]

What I did is breaking up the circuit at the batery (+) pole. Connect my multimeter in series between the batery (+) and all cables connected to the car. What I got is below. Engine is not running, doors closed, all lights are off. Alpine alarm on or off don't change the current drawn. Can someone please tell me that my current drawn look ok.

I tried to measure each cable/wire separately and found that all cables are getting 0 ma (even the biggest stock cable). The only cable keep drawing this current is one single cable connected to the fuse box (I guess). There are 2 cables wrap in a black plastic tube go to under the fuse box, this is one wire.

This cable controls eveything in my car, power windows, stereo, dash light, interior lights, alarm, etc.

Is this enough for you to tell me what is going on? I went though 3 different bateries and now I don't think all my bateries are bad. The longest I can park my car and can be able to start it is only a week to 10 days.

Thanks in advance.

[Cipotifoso]

Find out how much your clock is drawing - or disconnect it and see if you are still getting a current draw. Although I've never measured the current draw, it is the reason that I keep my battery hooked up to a battery tender all the time.

[Rusty Heap]

One good way to find a constant current draw, is to wire up your amp meter as you did, then start pulling fuses of each circuit and see how your mA draw changes, that way you can find the individual subcircuit that has a contant draw.

Also check your voltage both with car running and not, your 12.64 had better been with the car off, with it idling I'd expect to see 13.8 - 14.1 which showing your alternator and charging circuit is functioning okay.

[rnln]

THanks for suggestion.
I have a v gauge connected to the ignition inside. This is the V measured when key is off. At idle, yes, I have around 14.5v. As driving, the v increase slowly. Driving on highway for a while, it will hit closed to 15v, maybe 14.9.
My question now is about reading the multimeter. I am not sure what I am getting by reading the digit. Am I getting 0.5ma or I am getting 5ma?
Thanks.

[Rusty Heap]

the multi meter has different scales, each with different sensitivity.

on your 10 amp scale, rather large, you are reading .05 amps, which would be 50 milli-amps, pretty small draw, but this is at a very course reading on that scale.

when you switch down to the 2 milli-amp scale, the meter i( I believe) should have the leads plugged into the A plug on the meter, not the 10 amp plug. The 10 amp typically is fused, where as the A plug may not be fused hence the smaller current sensitivity.

So I think you're using the meter incorrectly. I could be wrong.

Couple of quick formulas for you.

Power (watts) = I (current) x V (volts)

Hence, a 100 watt fog light = ~ 8.5 amps X 12 volts.

And another;

I (current) = V (volts) / R (Resistance)


hope this helps. Move the lead over to the other A plug location and try your test again.

[morrisjm1]

I could be a bad diode in the alternator. Spent an hour pulling fuses with my neighbor with no drop in the current draw. Then we pulled the alt plug and it went to zero. He replaced the alt and hasn't had a problem. Of course, his car is Mustang and alternators are fairly cheap.

Good luck,
Mike

[scottbooth]

Rocky Heap has given a lot of good advice.

On my meter all of the current scales are fused, I know because I have blown the fuse .

On most meters, the difference between the 10 A scale and the lower ones is that the probe connection for the high-current scale is internally shunted to the "common" probe. The shunt bypasses most of the current so it doesn't all go through the meter. The meter then measures the voltage drop across the shunt and scales that to give you a current reading (using the same math Rocky provided). So the high current scale is definitely less precise - though it still may be good enough for what you are doing.

A typical process when dealing with a current draw of unknown magnitude draw is to use the highest current scale (as you have) to determine whether you can safely use a lower-current scale to troubleshoot with a little better info. In this case it sounds like you can. You will need to connect the red probe to the "mA" jack on the meter if you have one (I didn't get your pictures for some reason, don't mean to be dense). Then set your meter to the smallest scale whose max is higher than what you were reading, i.e. probably a 200mA or 500mA scale if you are seeing 50mA.

While troubleshooting using a lower scale, just remember not to do anything that will add a potentially large current draw (like opening a door with the dome lights activated, or turning on any of the dash switches, etc.) This is a good way to blow the meter fuse (if it has one) or kill the meter (if not).

My car used to drain its battery on its own too. I never bothered to troubleshoot it scientifically, but when I removed the aftermarket alarm, stereo and CD changer during the track car lightening process the problem went away.

Good luck, sounds like you are on the right track. The pulling-one-fuse-at-a-time plan should get you somewhere.

[rnln]

Thanks all much.

scottbooth,
When I plug the lead into the "A" port, there is nothing happen on all ranges setting. When the lead is plugged into the 10A port, set the metter at 2m setting, I got .005 on the LCD. Set the meter at 20m/10A, I got .05 on the LCD. Is this 5ma or 5a?
Thanks.

Rocky Heap,
Is 50ma small drawn? I read somewhere on this board, someone was saying must be below 1ma. If more than 1ma, then to much. Also if I have a small drawn, then why my batery keep going out in a week or so?

[Rusty Heap]

50 milla amps is very small, I'd bet even your clock would only draw 100-200 mA.

A healthy new battery should be able to give you 300-400 amp hours, which means 300-400 amps for one hour, like leaving your headlights on (most likely a 15 amp draw, for 15 hours) 15 x 15 300 amp hours.

Good question on why your battery(s) are going bad/low in such a short time..............intermittant near dead shorts (close to zero ohms) may be keeping your battery at a half charge status.

May I suggest getting a newer better volt meter, they're pretty cheap and most are auto-ranging now so you don't have to fiddle with your knob setting the range, sounds like your meter may be bad in the Amp setting, only the 10 amp range is working.

Some rough amperage draw, like I mentioned before, may be approximately 10 amps for a fog light, a stock radio stereo deck draws about 3-4 amps, ohms, and resistance, is 0 for a dead short ( like a short length of wire) A speaker is typically 4 ohms - 8 ohms. A light bulb is typically ~ 2-4 ohms.

As you seem to have a good charging system if it is putting out 14 some odd volts during running, then you also have something drawing amps out of your battery. A healthy charged battery should start your car even after sitting for 1-2 months, not 1-2 weeks.

You might take it to a place like Shucks or Pep boys, they will check your battery and charging system at the curb typically for free. The only real way to test a battery is to put a load bank on it, which typically is like a 100 amp load, to test the cold cranking amps as would be applied by your starter.

Get a new meter, have your charging system checked, and the last resort might be a battery disconnect master switch to isolate the battery from the whole car while not in use.

My alternator has an intermittant open, where sometimes it is putting out 14 volts while running, and sometimes not. I'm still chasing down this intermittent wiring issue, so I'm in your same boat......yes it's a pain in the asss!

dave

[rnln]

Rocky,
This is the third batery on this car so far this year. What you were saying about my meter make me think maybe you are correct. And if my meter is bad, then all my theory need to go back to the begining.

Since my Voltage gauge read a little high, you said "if it is putting out 14 some odd volts during running, then you also have something drawing amps out of your battery". If anything draw amps while the car is running, then do I need to worry about it, or it's ok?
Now I am so confused since the batery dead all the time, killed 2 bateries already, and I still have no clue. Every direction seem to be wrong.
Let me get another meter and let see. Please come back after I get more detail.
Thanks much for your time.

[911pcars]

rnln,
I couldn't see your uploaded images so I can't remark about the meter displays.

Open circuit voltage reading of a fully charged battery should be in the area of 12.6-13 volts. Typical charging voltage with engine running is around 14 volts. If the VM indicates less, switch on the headlights and other accessories and confirm the charge voltage rises.

It sounds like you're conducting a parasitic current loss test correctly. 50 ma is typical current loss. If current loss is excessive, remove one fuse at a time to isolate the circuit causing the discharge. Could also be a circuit not protected by a fuse (altenator, interior floor blowers, etc.).

If multiple batteries discharged, there is a problem. However, storage batteries are rechargeable. You shouldn't have to replace unless it can't be recharged. Do you have a trickle charger?

Sherwood

[rnln]

I still have not have a chance to go out and buy a diff. multimeter today, so maybe tomorrow.

911pcars,
I turned off my web server so... sorry. It's on now.

Are you saying is there is anything turned on during the driving, voltage will increase? This is not what happending in my car. What I have seen is decrease instead of increase.

I have a voltage meter installed in the dash. I connect the ground to chassis and (+) to the ignition so that it only run when the key is on. At idle, it shows 14.5v. After driving at constant high speed on freeway without lights or anything on for 15-20 mins, it'll show closed to 15v (maybe 14.9v). If I switch lights or AC on, the voltage will drop closed to 14.3v. Is this oposite to what it suppose to be? What do you think?

I just come back from a friend mechanic shop, replaced my starter. The starter is replaced now but I still hear the old weird sound once in a while when starting. The sound is loud. It sounds like the electrical spark sound but just much louder. When twisting the key, the sound come together with the engine starting. It just happen once in a while. Anyone know what it is?

[911pcars]

14.9 charging voltage is a little on the high side. I've seen specs of 14.7 V so this could be okay. Alternator output is determined by the voltage regulator. However, you stated two batteries have already "died". Can you describe their passing?

It could be that the higher-than-normal charging rate overheated the batteries and shortened their life.

When your mechanic replaced your starter, could he have checked the charging system as well?

Sherwood

[rnln]

Thanks Sherwood,

My car has always been "died" after a week or 10 days undriven therefore everytime starting it after a week or 10 days, I had to jump the batery. Slowly that "a week or 10 days" shorten to several days and to 1 or 2 days, then I replaced the batery. The first replaced, I thought becaus ethe batery is too old but when I took it out, it's only been less then 2 years. The second batery last less than a year. Now is the third.

When replacing the secnd batery, I also rebuilt the alternator (replacing VR, bearing, brush, etc), install the voltage gauge in the dash, etc.

Now the the voltage drop after a week or 10 is still there so I decided to measure the voltage/amps across the batery hopefully I can trace down the problem maker.

No, the mechanic didn't check the charging system since I didn't ask. I was only asking to replace the starter.

Back to my previous question, when I turn on additional components (AC, fan, radio, etc) while driving, do I suppose to see voltage increase or decrease?
Thanks.

[Wil Ferch]

For reference...a 3.2 era car has a "spec" stand-by draw of about 16 mA.
A later, 964 will have a spec stand-by draw of about 60-64 mA.

To expect it to be less than 1 mA is unreasonable. Above 100 mA would have me worry.

- Wil

[911pcars]

"Back to my previous question, when I turn on additional components (AC, fan, radio, etc) while driving, do I suppose to see voltage increase or decrease?"

Not to be evasive, but it depends. Whenever a load is switched ON, there will be a voltage drop in the system. However, the charging system should create enough voltage to prevent the battery from discharging. The output of the charging system should be more than the total load of the switched accessories. if not, the battery will discharge.

Your recent rebuild may have cured the charging system. However, from your latest symptoms, it seems like you have a parasitic current drain somewhere in the system. Until you locate it, either connect a battery maintainer to the system (low amperage charger) or disconnect the battery from the system between use.

Sherwood

[rnln]

more info but doesn't help...
I bought another multimeter yesterday. Today, I came to the car with the hope of finding out the current drop but disapointed because the result is the same as with my old multimeter.

With the red lead to the mA port, notthing shown. I switch the red lead to the 10A port and result is the same as my old multimeter, current is shown as 0.06.

I keep thinking the number above meant 60mA but thinking about it carefully with calculator, I think it is 600mA. I am correct? Because when I measured the trunk light (bulb indicate 12v 10W) my multimeter shown closed to 0.8. This is 8A.

Also because it is 600mA therefore when the lead plugged into A port, it won't work because for this port, it's only max at 200mA.

Please comment.

[911pcars]

Amps x 1000 = milliamps (mA)

Ex.
.06 amps x 1000 = 60 mA

Is the above the total current draw from the entire electrical system? The ammeter should be in series with the negative ground wire and the battery.

If so, you should be okay. If the above result is measured from only one fuse position, there may be other circuits leaking current.

Sherwood

[rnln]

That is from entired system. I can't measure the Alpine alarm itself because it is connect to the system somewhere in the car, not at the battery. None of the fuse in the fuse box is for it either. I have to rip the dash to find the brain and the fuse.

".06 amps x 1000 = 60 mA"
but the multimeter set at 10A = 10x. That is 600mA. Am I correct?

If I am correct. Or maybe I am not but assume it's 600mA. Pulling the alarm fuse got me down to 270mA.

Now I don't know what to pull to get me down to 10mA. I pulled the dom light and broke it completely because it's too old, maybe right here, I found that it only has 2 wires, (+) and (-). There is no wire connect to the door switch. This is what I suspect since when I open the dorr, this dom light never come up, and my power windows never stop working. I think maybe this another source of voltage lost.

Another thought, why after market alarm always has this problem? Is the unit itself go bad after time and suck more power, even when not armed? Or is it the bad installation job does it?

More info comming soon.

[911pcars]

Typically, the 10A test lead jack is used to measure current less than 10A max. but more than the other available scales. The reading is what it is. 1.0 is 1 amp. .06 is 6/10s of an amp or 60 mA (.06 x 1000), and all the way up to 10 amps.

Multimeter scales are by no means universal. Did your meter include a booklet to help translate the various scales on your meter?

This might help:
http://www.allaboutcircuits.com/vol_1/chpt_8/8.html

Sherwood