i want to see if a short is causing a drain on my car battery.

i have a digital multimeter. one way i theorized was to connect it in
series with the battery via the earth lead and negative terminal.


is this logic sound? or will i fry my multimeter? is there any other
way to find a short (apart from scraping the earth lead to the neg
terminal to see if it arcs - which on my car it doesnt)

thx

beerismygas wrote:
i want to see if a short is causing a drain on my car battery.

i have a digital multimeter. one way i theorized was to connect it in
series with the battery via the earth lead and negative terminal.


is this logic sound? or will i fry my multimeter? is there any other
way to find a short (apart from scraping the earth lead to the neg
terminal to see if it arcs - which on my car it doesnt)

thx

Determining if you have and finding are two different tasks.
One simple thing you can do is put a light bulb in the path.
If it glows, you've got leakage. If it doesn't glow, put the multimeter
on the 10-amp scale across the light bulb and see what you measure.

Modern cars have all sorts of electronics that runs in the background.
It's not at all clear what kind of transient current happens when you
power it up. The lightbulb procedure protects your meter against
these unforseen transients.

To find the "short" the easiest thing is to borrow a DC current probe
and trace the wire that has the current.
mike

--
Return address is VALID!
Bunch-O-Stuff Forsale He
http://mike.liveline.de/sale.html

beerismygas wrote:
i want to see if a short is causing a drain on my car battery.

i have a digital multimeter. one way i theorized was to connect it in
series with the battery via the earth lead and negative terminal.


is this logic sound? or will i fry my multimeter? is there any other
way to find a short (apart from scraping the earth lead to the neg
terminal to see if it arcs - which on my car it doesnt)

thx

Hi...

It surely won't harm your multimeter (used properly, of course),
but on the other hand won't tell you much of interest either.

Today's cars use an awful lot of stuff that draws power continuously
that you will find some current drawn even though all is fine.

Physically check the obvious stuff for starters. Trunk light,
hood light, glove box light, for instance. Going off when closed?
Young folks music stuff... power amp switching off?

Take care.

Ken

beerismygas wrote in
oups.com:

i want to see if a short is causing a drain on my car battery.

a short would blow a fuse.

Maybe your car battery is going bad.
They only last about 4 years,less if you let them deep discharge.

i have a digital multimeter. one way i theorized was to connect it in
series with the battery via the earth lead and negative terminal.

In modern cars,it's normal for some current to be drawn even with the car
not running,accessories and lights off.


is this logic sound? or will i fry my multimeter? is there any other
way to find a short (apart from scraping the earth lead to the neg
terminal to see if it arcs - which on my car it doesnt)

thx





it would HELP a lot if you said what make,model of auto,mods,options,the
more info you give the better.

You can pull fuses one by one to isolate an excess current draw to one
circuit.


--
Jim Yanik
jyanik
at
kua.net

beerismygas wrote:
i want to see if a short is causing a drain on my car battery.

i have a digital multimeter. one way i theorized was to connect it in
series with the battery via the earth lead and negative terminal.


is this logic sound? or will i fry my multimeter? is there any other
way to find a short (apart from scraping the earth lead to the neg
terminal to see if it arcs - which on my car it doesnt)

thx


A short will blow a fuse or burn a wire.

Intentionally trying to make a spark at your battery terminal is
dangerous. Car batteries produce explosive hydrogen gas when charging,
and a spark can cause the battery to explode - spraying you with acid
and debris, possibly blinding you or severely burning your skin.
Car battery explosions are rare, but not impossible. They DO happen and
the result can be devastating.

You can track down a current drain by connecting your meter between the
positive battery lead and the battery (with the car OFF) and removing
fuses one at a time.
If you try to start the car or use any high amperage circuits while
doing this test - like the wipers, blower motor or rear defroster - you
will likely blow your meter's fuse or damage or destroy your meter.

its a, (cough) 1985 ford escort. no electronics.

You can track down a current drain by connecting your meter between the
positive battery lead and the battery (with the car OFF) and removing
fuses one at a time.

i will try this on the 10A meter setting to begin with and lower it
till i get to the milliA.

"beerismygas" wrote in message
oups.com...
i want to see if a short is causing a drain on my car battery.

i have a digital multimeter. one way i theorized was to connect it in
series with the battery via the earth lead and negative terminal.


is this logic sound? or will i fry my multimeter? is there any other
way to find a short (apart from scraping the earth lead to the neg
terminal to see if it arcs - which on my car it doesnt)

Don't forget that the battery itself or the charging system could be at
fault.

i measured it. not even an microamp of leakage

and as a control I turned on the courtesy light and measured again.
360 milliA of current

i also discovered the pulley belt was caked in oil and needs
attention, this would explain lack of charging

thx for your input

"beerismygas" wrote in message
ups.com...

i measured it. not even an microamp of leakage

and as a control I turned on the courtesy light and measured again.
360 milliA of current

i also discovered the pulley belt was caked in oil and needs
attention, this would explain lack of charging

Ah yes, the belt ... happened to me once ... hope that your problem is over.

"Charles" wrote in message
news

"beerismygas" wrote in message
ups.com...

i measured it. not even an microamp of leakage

and as a control I turned on the courtesy light and measured again.
360 milliA of current

i also discovered the pulley belt was caked in oil and needs
attention, this would explain lack of charging

Ah yes, the belt ... happened to me once ... hope that your problem is
over.

Just a couple of thoughts.

Have you rechecked the radio now that you've had the battery disconnected ?
It will have lost its code if one had been put in, and if you don't know it
....

Also, depending on how long the battery was disconnected for, the EMU may
need to 'relearn' the engine, and there is a procedure of engine starts,
stops, and driving and idling sesions to make it do this.

Arfa

On Jun 27, 1:09?pm, beerismygas wrote:
i want to see if a short is causing a drain on my car battery.

i have a digital multimeter. one way i theorized was to connect it in
series with the battery via the earth lead and negative terminal.

The usual way is to connect the meter between the positive battery
terminal and the positive lead after it is removed from the battery.

Bob AZ

"beerismygas" wrote in message
ups.com...

i measured it. not even an microamp of leakage

and as a control I turned on the courtesy light and measured again.
360 milliA of current

i also discovered the pulley belt was caked in oil and needs
attention, this would explain lack of charging


You might want to lok into the source of the oil. Leaky power steering
pump or hose?

Bob

i did that, but with the negativ lead as its easier to unscrew. the
result should be the same.

You might want to lok into the source of the oil.

the source of the oil? its like a black hole down there. engine needs
re gasketing from top to bottom me thinks. dont have power steering

thx

In article . com,
beerismygas wrote:
i measured it. not even an microamp of leakage

That's unusual. Most cars have devices which are powered all the time.
(radio station memory, etc)
Something like 20mA quiescent is normal.

and as a control I turned on the courtesy light and measured again.
360 milliA of current

That's 4 watts or so. Not much courtesy there. ;-) I'd expect a lot more.

i also discovered the pulley belt was caked in oil and needs
attention, this would explain lack of charging

--
*Organized Crime Is Alive And Well; It's Called Auto Insurance. *

Dave Plowman London SW
To e-mail, change noise into sound.

In message , "Dave Plowman (News)"
writes
In article . com,
beerismygas wrote:
i measured it. not even an microamp of leakage

That's unusual. Most cars have devices which are powered all the time.
(radio station memory, etc)
Something like 20mA quiescent is normal.

and as a control I turned on the courtesy light and measured again.
360 milliA of current

That's 4 watts or so. Not much courtesy there. ;-) I'd expect a lot more.
Surely that's about right? The rear lights are 6W, and the stop lights
21W. I wouldn't expect a courtesy light to be very much.

i also discovered the pulley belt was caked in oil and needs
attention, this would explain lack of charging


--
Ian.

You could also test your ground to see if it is causing poor
recharging.. has happened to me before. Set multimeter to check for
resistance.. put on lead on negative battery terminal and second lead
on a ground.. preferrably the one your alternator grounds to.

In article ,
Ian Jackson wrote:
That's 4 watts or so. Not much courtesy there. ;-) I'd expect a lot
more.

Surely that's about right? The rear lights are 6W, and the stop lights
21W. I wouldn't expect a courtesy light to be very much.


My car has four 21 watt ones on a timer/dimmer. The idea surely is to
light the inside of the car when it's dark. Perhaps to read something.

--
*I'm not a complete idiot, some parts are missing *

Dave Plowman London SW
To e-mail, change noise into sound.

beerismygas wrote in
ups.com:


i measured it. not even an microamp of leakage

and as a control I turned on the courtesy light and measured again.
360 milliA of current

i also discovered the pulley belt was caked in oil and needs
attention, this would explain lack of charging

thx for your input



next Q is;WHY is the belt caked in oil??

--
Jim Yanik
jyanik
at
kua.net

i checked the bulb and compared it to the user manual specs, its a
5w. so the meter read correctly.

maybe one of these days i will get slapped on the face when i open the
door for a lady friend to get in - "Pervert! i am not a 5W kind of
girl!"

On Thu, 28 Jun 2007 00:17:33 GMT, "Arfa Daily"
wrote:



Also, depending on how long the battery was disconnected for, the EMU may
need to 'relearn' the engine, and there is a procedure of engine starts,
stops, and driving and idling sesions to make it do this.

My curent car, a 95 Lebaron, and my previous one, an 88 Lebaron, are
supposed to be like this, but I can never tell the difference after
the battery is reconnected. Seems to work the same.

Arfa


If you are inclined to email me
for some reason, remove NOPSAM :-)

On Wed, 27 Jun 2007 13:09:26 -0700, beerismygas
wrote:

i want to see if a short is causing a drain on my car battery.

i have a digital multimeter. one way i theorized was to connect it in
series with the battery via the earth lead and negative terminal.


is this logic sound? or will i fry my multimeter? is there any other
way to find a short (apart from scraping the earth lead to the neg
terminal to see if it arcs - which on my car it doesnt)

thx


My battery was dead if I didn't drive it every 16 or 24 hours, I
forget which. So when I went away for Thanksgiving, I disconnected
one side of the battery, and the battery was still able to start the
car when I got back 3 1/2 days later. So I was using too much current
when the car was off. (I already knew the battery was charging
propertly.)

If using s light bulb to find a short, Pat Voss (the smartest car guy
I know (via the radio)) recommended a #53, I believe it is. The guy
has lots of meters, but I got the idea he thought a lightbulb was the
easiest way. A 53 should be a bayonet mount, with the outer ground
and one center contact, and a spherical glass not much bigger than a
1/4 inch. Used for dashboard illumination and little things like
that. If a 53 doesn't look that, it's possible I got the number
wrong. Get back to me. Delete nopsam.

I expect this will be in the self-service part of a consumer autoparts
store, but there are so many new bulbs in the last 20 years that maybe
not everywhere

It worked for me when I had an extra alarm accessory that ran all the
time that was running down my battery. The bulb glowed then, but not
after I removed the accessory. The clock in the radio is not enough
to light a 53. Of course I already suspected the burglar alarm, and
just didn't realize the beeper transmitter in that particular case
used power all the time, not just when it waa alarming.

I see it was probably the belt. That's actually the first thing to
check. EVen if they are not dirty, they stretch with age. Even if
they are dirty, you can probably just tighten the belt.

Ihaven't read the rest of the thread, but I'm sure they told you about
removing the battery from the circuit and using the ohmmeter part of
the meter. You should make sure the voltage of the ohmeter is in the
same direction as the car battery.


You didn't say what year or make or model of car. You should have.
Late in the thread we find out that it has no powersteering. So it's
not the typical car everyone was thinking of, but even if it were
typical, you should give this kind of info.

If you are inclined to email me
for some reason, remove NOPSAM :-)