Hey all. Hope y'alls day goes great. A neighbor has an issue with their 98 Caravan SE. After it sets a few days the battery is drained. They purchased a new battery and again after a few days of not being started it drains again. They have had it tested and recharged, battery is good and charging system in van checks out good. They would like me to track down if there is a short in the system somewhere. I have never done that so I am asking you folks how can I track it down? If someone can tell me how to check each system that would be great. It is an elderly couple and can't afford to pay what it could cost to track it and repair it. So if you guys can help me save them some money that would be great. Thanks in advance.
Tracking down a short
- Thread starter HemiPar
- Start date
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SleeperScamp
Well-Known Member
Disconnect the neg battery cable and hook your test light to the neg post on the battery and the other end to the neg cable.. The test light should light up if there is a draw on the battery.. With the light glowing start pulling fuses until the light goes out.. At this point you know what circuit is draining the battery.. Then the real fun begins.. Hope this makes sense.. Good luck...
I hope I am correct on this so here goes..
#1 using a volt meter to see the voltage draw by removing the
negative battery post, attach one lead to the battery negative post
and the other to the ground wire you removed and see what amount
of draw there is ( DC volts setting or use a light tester )
with the key shut off and pull the light bulb under the hood if there is one.
Pull each relay and fuse till you see the gage drop.
this will get you to the circuit that is drawing current as it sets..
The first thing I would do is when it is totally dark outside make sure the clove box, interior and all lights are off and not on...
I believe there are many lights in these vans, even under the passenger set storage but not sure if there is one on this van.
Anything that stay powered up with the key off is where you want to look......... I hope a good tec jumps in here soon so you can help these elderly folks.
#1 using a volt meter to see the voltage draw by removing the
negative battery post, attach one lead to the battery negative post
and the other to the ground wire you removed and see what amount
of draw there is ( DC volts setting or use a light tester )
with the key shut off and pull the light bulb under the hood if there is one.
Pull each relay and fuse till you see the gage drop.
this will get you to the circuit that is drawing current as it sets..
The first thing I would do is when it is totally dark outside make sure the clove box, interior and all lights are off and not on...
I believe there are many lights in these vans, even under the passenger set storage but not sure if there is one on this van.
Anything that stay powered up with the key off is where you want to look......... I hope a good tec jumps in here soon so you can help these elderly folks.
kman521
Well-Known Member
Not miliohms or you will blow your meter if there is any voltage on there.
Set it to voltage.
67Dart273
Well-Known Member
Sorry guys you are both incorrect.
START using a test lamp and not a meter. This is because you could have a short "trying" to burn down the main battery cable of hundreds of amps, and using a test lamp will not hurt anything, including the lamp. It is it's own "self limiter."
If you cannot SEE the lamp glow, or it's so dim that it's difficult, THEN switch to your meter, but set the meter to the HIGHEST current (amperage) setting on the meter. ON most meters this will be a separate probe jack for 10 or 20A
If that reading is low and difficult to resolve, THEN drop down to milliamps, (thousands of an amp)
Most meters have a high end milliamps scale of at least 200 ma, which is .2 (nearly 1/4) amp. Most tests lamps draw MORE than 200ma, so if the lamp is glowing brightly, don't hook your meter up to a 200ma scale, if that is the most your meter will handle.
On the "typical inexpensive meter" below, you can see that 10A is in RED, and there is a separate probe jack, top one of the three.
Then the meter drops from 10A all the way down to 200ma, when you must switch the probe to the middle hole
Also, along with pulling fuses, don't be afraid to pull relays. Most newer rigs have a separate fuse panel as well as a box under the hood.
Also one of the "second" things I do if no fuse or relay solves the problem is to pull the alternator wiring. On older cars like our A bodies, all you need to do is disconnect the output wire from the stud. "Leaky diodes" in the alternator.
kman521
Well-Known Member
If you have a volt meter connected in series with the negative terminal and you have the meter set to voltage you will not burn anything. You will only read if there is voltage flowing which is the same as having a dull lit test bulb burning.
Your method is more involved and more detailed and it works too.
Regards,
Thank you for keeping me in line men, I need to let the pro's jump in on these threads some times :coffee2:
Along with the above, keep in mind there are several systems that will have a slight draw on the battery. The radio memory, security system (if it has one), also the pcm "keep alive" that stores previously learned information. Being an older couple how long does the vehicle sit ? It could just be that its a long time between being operated and the sum of the " normal" draws on it are pulling it down. The relays are a very good thought also, there could be some hanging. They are fairly easy to check with a vom. If you isolate it down to a specific feed and there is a relay involved, pull it and ohm it out. The schematic is usually printed on the side, to see if its sticking. I've seen some in another career field be hung and acutally release and actually click once removed and tapped. Which is also a good troubleshooting method. If you isolate down to a circuit and there is a relay, try tapping lightly with a screw driver handle to see if the draw goes away. Hope some of this helps.
kman521
Well-Known Member
67Dart273
Well-Known Member
Sorry, again, incorrect.
A voltmeter will tell you NOTHING. This is because a voltmeter draws almost ZERO current, and will show a reading at very very low leakage current. Hell try this:
Find one of your cars with a little dirty battery. This might be tough in the modern day and age. Stick one probe of your voltmeter on the hot post of the battery, then probe around different spots on top of the battery CASE
If there's enough moisture and dirt on there, YOU WILL get a voltage reading.
That is WHY some of my posts are this involved. You must measure CURRENT, not voltage.
kman521
Well-Known Member
I really didn't want to get into a pissing match about this but I am correct.
Sorry to the OP and we can take it to pm's if you want to discuss it.
If you put a volt meter in series with a load you will read voltage which is exactly what you are doing with a volt meter going in series with the negative terminal. If there is some load the meter will read but if the circuit is open you will get no reading.
The meter set to voltage is nothing more than an analog test bulb.
If you connect a bulb(load) in series with a volt meter and a battery the volt meter will read voltage but not the full battery voltage. If the load was a dead short you will read the originating voltage but if the load has any resistance the voltage reading will be less than the source voltage.
Try it and you will see.
67Dart273
Well-Known Member
I don't know why it is that suddenly this is a "pissing match."
The FACT (not piss) is that you are incorrect.
That does not make you a lesser person, you are simply incorrect
THERE IS ENOUGH parasitic load on ANY car (even older cars, diode leakage or just plain dirt and corrosion) that a voltmeter and ESPECIALLY a modern high impedance digi meter, will simply show battery voltage with NO load other than NORMAL parasitic drain.
And..............any modern car with a memory device, IE radio or engine computer will MOST CERTAINLY show battery voltage if a voltmeter is used in this manner.
THE FACT is that using a voltmeter as you describe shows you NOTHING meaningful. NOTHING
You MUST measure current.
34072demon
Active Member
Current is the flow of electricity (electricity being used).
Voltage is the potential difference of the source of electricity.
Measure current.
Voltage is the potential difference of the source of electricity.
Measure current.
Inertia
Well-Known Member
The Alternator is not fused/relayed,.. and can cause a draw,
so one of the diss-connects should be the alt, both plug, and the heavy wire to the stud,, ...
so one of the diss-connects should be the alt, both plug, and the heavy wire to the stud,, ...
kman521
Well-Known Member
LOL, Now I get what you are saying.
ops:I wasn't wrong that there would be a reading using a volt meter in series if there is a load, just that that reading would be pretty much useless because there will always be some parasitic load which is a given with all the modern electronics and other variables. I thought you were saying that you would not get any reading on the volt meter.
Sometimes things get lost in translation.
Your methods of testing are well thought out and detailed.
Cheers,
jabdusty57
Well-Known Member
67Dart273 is dead on in his explanation. A voltmeter measures potential across a circuit (+ to -), not in series with that circuit. The ammeter properly connected in series will tell you accurately how much current is flowing through that circuit. These principles are very easy to verify by searching the web for basic electrical theory.
good stuff... subscribed to thread
67Dart273
Well-Known Member
Fair enough
Here's a setup to illustrate just how little current a modern voltmeter draws. The meters in the photo are hooked as in up in the drawing. All in series, you have:
1--HP analog VOM set to .25ma full scale (That is only 250 micro amps, or "not very much". As you can see, it is barely off zero, inconsequential amount of current
2--Fluke 79 set to it's lowest current scale, 40ma. It is reading .001ma which may not be accurate. If it IS accurate, that is ONE microamp, a terribly tiny amount of current.
3--Fluke 77 still wired in series as per the diagram, reading full supply voltage, nominally 12V
In other words it is taking a TINY amount of current to operate that voltmeter, and I can assure you that 1 microamp is never EVER going to drain a battery, before it's internal chemistry does so
kman521
Well-Known Member
Awesome, Thanks for that.
Looks like the ammeter method is the only true way to test for drain on the battery. I never really thought about the high internal resistance of a volt meter.
Live and learn.
Lonewolf3165
Living the Dream!
FWIW, Yes you should use an ammeter since what you need to know is the current draw. If it hasn't been stated here already, connect it in series between battery negative post & the neg cable with meter off.
Touch the negative cable to the battery post & hold it there. Now turn ON the meter & set to the highest ampere scale (10a or 20a on some meters). After waiting with the neg cable still touching the battery post for 30 seconds to time out the electronic timers in the car, remove the battery cable away from the battery post with the meter connected in series & measure your amps. If its not enough to show on the meter repeat the procedure on the next lower scale. Note: You must keep the cable in contact with the battery & time out the electronics every time you remove & reconnect the meter or you risk blowing the internal fuse in the meter.
50-60 milliamps(ma) is considered acceptable for most commonly equipped computer controlled vehicles today. If it's higher remove fuses 1 at a time & observe your meter drop. If no change or minimal, reinstall the fuse & keep going until you find the 1 that gets it under spec. Then that's your problematic circuit. Now you are only 1/2 way home! You need to find everything that operates on that fused circuit & check those components, circuits & sub-circuits. And don't open the door with the meter connected or the dome light will make the fuse in the meter blow! You can turn off or disconnect the light 1st to be safe if you're sure that's not the draw.
PM me with an questions if you'd like.
These vehicles are notorious for bad body control modules causing problems. You would need one with the same part # & calibration to replace it & they aint cheap. I have also seen trouble in the wire harness under the hood that wraps over & around the transmission near the air box. But it could be anything.
I hope this helps.
Touch the negative cable to the battery post & hold it there. Now turn ON the meter & set to the highest ampere scale (10a or 20a on some meters). After waiting with the neg cable still touching the battery post for 30 seconds to time out the electronic timers in the car, remove the battery cable away from the battery post with the meter connected in series & measure your amps. If its not enough to show on the meter repeat the procedure on the next lower scale. Note: You must keep the cable in contact with the battery & time out the electronics every time you remove & reconnect the meter or you risk blowing the internal fuse in the meter.
50-60 milliamps(ma) is considered acceptable for most commonly equipped computer controlled vehicles today. If it's higher remove fuses 1 at a time & observe your meter drop. If no change or minimal, reinstall the fuse & keep going until you find the 1 that gets it under spec. Then that's your problematic circuit. Now you are only 1/2 way home! You need to find everything that operates on that fused circuit & check those components, circuits & sub-circuits. And don't open the door with the meter connected or the dome light will make the fuse in the meter blow! You can turn off or disconnect the light 1st to be safe if you're sure that's not the draw.
PM me with an questions if you'd like.
These vehicles are notorious for bad body control modules causing problems. You would need one with the same part # & calibration to replace it & they aint cheap. I have also seen trouble in the wire harness under the hood that wraps over & around the transmission near the air box. But it could be anything.
I hope this helps.
67Dart273
Well-Known Member
Makes our old beaters look pretty good, eh? I bought a 98 Ranger knowing it had a problem. It had (I moved it) a module buried under the plastic upoulstry in the back of the cab which runs the key fob receiver and the theft alarm. You MUST manually lock the last door closed manually, and NOT arm the theft alarm, or in 30 seconds to a 1/2 day, the alarm WILL eventually go off.
THANKS, Ford!!
THANKS, Ford!!
Dubob, After the the new battery then again after a charge it only sat for 3-4 days.
They have another vehicle to get around but SHE really likes her van. With my hours at work, I can't look at it for a couple days. I have the battery disconnected right now. But here in a few minutes I will go out, connect battery and see what happens.
I wanna thank everyone for the response. It looks like I use a Test light/meter (on the correct setting) between cable and post. then pull fuse/releys to find the system with the draw. Again thanks.
Lonewolf3165
Living the Dream!
It's important to do everything in the correct order otherwise you'll get confusing readings &/or blow the fuse in the meter. Use a meter if possible. A test light is only gonna leave you guessing. A meter will give you actual results. An inexpensive meter will work just fine. Sears sells them for around $20 & up. If you don't have one its money well spent because you can use it virtually forever on so many things.
Good luck.
kt340sport
Well-Known Member
I was going to say check out 67dart273 but i see he is already on the job.
cudajim
cudajim
Yea, I'm going with a current measurement here too. You're looking for a current draw, probably in the mid milli-amp range if it's draining a battery fairly quickly. I would expect micro-amps or low milli-amps of current to be flowing in the "keep alive" circuits.
I recently worked on a VW which had the same problem. It turned out to be a leaky diode in the alternator drawing current and draining the battery after about 3 days. A new alternator fixed the problem.
I recently worked on a VW which had the same problem. It turned out to be a leaky diode in the alternator drawing current and draining the battery after about 3 days. A new alternator fixed the problem.
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