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#1
Old 01-13-2014, 09:56 AM
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Car wonks: Identifying Parasitic Drain.

My commuter car is a 2000 VW Jetta GLX. It has a little over 190,000 km on the odometer. It's been reliable for most of its life and I've taken excellent care of it. Recently I've noticed odd electrical gremlins. Something is draining the battery while the car is sitting parked. I'm absolutely anal about turning off everything before I shut off the engine so it's not like I'm leaving the lights or radio on overnight. I had the battery replaced last year. The car has been starting and operating fine until about a month ago. I notice that it hesitates slightly before starting on a cold morning. Starting through the day after that is not an issue. So the alternator is charging the battery just fine, I assume. Had the car in for service last week and asked them to test the battery... test came back A-OK. Parked the car for the weekend and this morning came out to find the car completely dead. Even the LCD clock was dead. Battery completely drained. Didn't bother trying to boost it because I didn't have time. But once I get it started and let it charge the battery, I'm pretty sure it will be drained again a day or two later.

I assume there is parasitic draw that's killing the battery. Is that a safe assumption? What's the correct method of identifying the source of the draw? Is a standard handheld electrical multi-meter sufficient to monitor the current?
#2
Old 01-13-2014, 10:02 AM
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Check for a draw at the battery (with a multimeter), pull fuses till it goes away, that is your bad circuit.

Keep in mind there can be a draw from radio memory/clock etc, you're looking for something more than that.
#3
Old 01-13-2014, 10:10 AM
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How do I connect the multimeter? In line or parallel with the battery?
#4
Old 01-13-2014, 10:42 AM
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As a follow up question... given that my battery seems to be fully drained now, am I looking at having to replace the battery or can I expect it to function normally once it's fully charged again?
#5
Old 01-13-2014, 10:50 AM
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It is a reasonable assumption that there is excessive parasitic drain on the battery. The other possibility is that the battery will no longer hold a charge properly, but that's unlikely with a one-year-old battery. Note, however, that the battery's life has been compromised due to its being deeply discharged, and the more times it gets drained like that the shorter its life will be.

The drain can be tested with an ammeter that measures milliamps. Your multimeter may or may not have this function. There might be a workaround way to check it without an ammeter (maybe using a voltmeter or a test light), but if so I don't know the details of how to do that accurately.

With an ammeter, it is hooked up inline. With the negative battery cable disconnected, the meter's negative/common test lead is attached to the battery's negative post and the positive lead to the battery terminal of the negative cable. A reading of (roughly) 60 mA or less would be normal. If there's a significantly higher reading, the procedure is as Vagabond said. Pull the fuses one at a time until the reading drops to a normal level; the last fuse pulled will be for the affected circuit. Note that the fuses for normal drain items (clock, computer memory, etc.) will have a small affect, but you're looking for a bigger difference. If pulling fuses doesn't reveal the drain, disconnect the wires to the alternator -- it can have a drain even if it's charging okay. If the drain is in the alternator, replace it.

If the drain is associated with a particular fuse, reinstall the fuses, then locate and disconnect each component on that circuit until the drain goes away, and replace the relevant item.
#6
Old 01-13-2014, 10:58 AM
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The battery could be shorted internally. Even a year old battery can go bad.

I've seen batteries with so much gunk on them that they short across the poles. Put a multimeter on the positive pole and probe other spots on the battery to see if you get any readings. Use the amp setting.

Once saw a wrong sized battery that was too tall. The top posts would touch the insulation blanket under the hood which would drain the battery especially when wet.

Does your car have a light under the hood or trunk? Sometimes these don't turn off. Remove the bulb.

If you can't find the problem, consider getting an under-hood battery disconnect switch. A PITA but better than a dead battery.

http://harborfreight.com/battery...tch-97853.html

Last edited by JerrySTL; 01-13-2014 at 11:00 AM.
#7
Old 01-13-2014, 11:48 AM
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First place I checked was the battery terminals and connections. Battery is relatively new and connections look clean (no gunk). Short across the terminals doesn't look likely as there is no insulation under the battery cover and sufficient clearance. No engine compartment light, if memory serves. When I parked the car on Friday night it was already dark so I would have noticed if the cabin lights were accidentally left on.

Thanks for the instructions and tips, all.
#8
Old 01-13-2014, 01:54 PM
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Quote:
Originally Posted by QuickSilver View Post
My commuter car is a 2000 VW Jetta GLX.
Found the problem.
#9
Old 01-13-2014, 02:17 PM
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Originally Posted by ReticulatingSplines View Post
Found the problem.
Oh, snap.
#10
Old 01-13-2014, 04:01 PM
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You are assuming that parasitic draw is the culprit.
I propose that you don't assume anything.
Did you actually charge the new battery with a charger or just drive around?
My first concern is that the battery isn't being fully charged.
Do the headlights get brighter when you give it a bit of gas from idle? They should.
Voltage meters can be found for $10-$15.
Measure the voltage of the battery w/ the car off. A reading lower than 12.4 volts means that your battery needs to be charged.
Then measure at the battery with the car at about 20% throttle. A functional charging system will produce between 13.5 and 14.5 volts. If it's much more than that, you can actually cook the battery which shortens it's life. Some cars have voltage regulators. Most newer cars have it built into the alternator.
Next; are the starter bearings worn and causing substantial resistance, causing extreme load on the battery. Most any auto-parts place will test your starter if you can remove it and get it to them.
#11
Old 01-13-2014, 04:13 PM
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Quote:
Originally Posted by QuickSilver View Post
How do I connect the multimeter? In line or parallel with the battery?
In line. set for ampers

Last edited by Vagabond; 01-13-2014 at 04:13 PM.
#12
Old 01-13-2014, 04:43 PM
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Had the same problem once with a 2002 Passat. Turned out to be the trunk light switch. The trunk would close, and lock, but the light wouldn't go off. I fixed it. I think (I can't remember for sure) the light switch was part of the lock/latch mechanism, and I replaced all or part of that mechanism. That took care of the problem.
#13
Old 01-14-2014, 05:35 AM
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Quote:
Originally Posted by HipGnosis View Post
You are assuming that parasitic draw is the culprit.
I propose that you don't assume anything.
Did you actually charge the new battery with a charger or just drive around?
Battery was fresh off the Interstate truck. It was installed by the shop that services my car. Which isn't a guarantee that it was fully charged or that it's not defective in some way.

Quote:
Originally Posted by HipGnosis View Post
My first concern is that the battery isn't being fully charged.
That had occured to me as well.

Quote:
Originally Posted by HipGnosis View Post
Do the headlights get brighter when you give it a bit of gas from idle? They should.
They do. Ever so slightly.


Quote:
Originally Posted by HipGnosis View Post
Measure the voltage of the battery w/ the car off. A reading lower than 12.4 volts means that your battery needs to be charged.
Then measure at the battery with the car at about 20% throttle. A functional charging system will produce between 13.5 and 14.5 volts.
Battery was tested when I had the car serviced last week (oil & filter). Checked out. Saw the test readout.

Quote:
Originally Posted by HipGnosis View Post
Next; are the starter bearings worn and causing substantial resistance, causing extreme load on the battery. Most any auto-parts place will test your starter if you can remove it and get it to them.
This is food for thought. Yep, starter issue has been an on/off thing for a couple of years now. Every so often, when I start the car, the starter will grind. Like the starter gear (clutch?) doesn't retract in time and when the engine catches there is a brief but annoying sharp grinding noise. Additionally, the cold starts this winter have sounded like the battery has been under more load than I'd expect at these temps (at or below freezing in the morning). There's this brief pause when you first turn the key where for a second I'm not sure whether the engine will turn or not. Almost like the dull hum of an electric motor under too heavy of a load. You may very well be right about the starter being the possible cause.
#14
Old 01-14-2014, 06:17 AM
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I realize your car is a VW, and I'll be talking GM, just bear with me.

GM in general had a production problem where the positive (red) ring terminal on the back of the alternator was done improperly, and as the car aged, the copper wire in contact with the terminal crimp would oxidize, creating just enough resistance that the battery would not charge if the headlights were on. I had the problem in both a Chevette and a Pontiac, it was a real bastard to find in the Chevette. When the Pontiac did it to me, I knew what to look for and fixed it myself in about 15 minutes.

Take the red terminal off the alternator, and try to gently flex it. If the terminal breaks off, cut off about an inch of wire and crimp on a new terminal. Done.
#15
Old 01-14-2014, 08:55 AM
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Quote:
Originally Posted by QuickSilver View Post
Quote:
Originally Posted by ReticulatingSplines View Post
Quote:
Originally Posted by QuickSilver View Post
My commuter car is a 2000 VW Jetta GLX.
Found the problem.
Oh, snap.
No, really. 14 years old, east coast weather & salts, Pontiac of European cars. Just run it into a light pole--it doesn't have to be a bad wreck to total it. Dude, it could be dozens of things, each more invisible than the next.

Last edited by Inigo Montoya; 01-14-2014 at 08:56 AM.
#16
Old 01-14-2014, 09:42 AM
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Originally Posted by The Great Sun Jester View Post
No, really. 14 years old, east coast weather & salts, Pontiac of European cars. Just run it into a light pole--it doesn't have to be a bad wreck to total it. Dude, it could be dozens of things, each more invisible than the next.
Is this your professional advice, Mr. Insurance Adjuster?
#17
Old 01-14-2014, 10:10 AM
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Touche'! Fraudulent claims and intentional acts are, of course, frowned upon and unacceptable in polite society.
#18
Old 01-14-2014, 10:24 AM
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Quote:
Originally Posted by QuickSilver View Post
Yep, starter issue has been an on/off thing for a couple of years now. Every so often, when I start the car, the starter will grind. Like the starter gear (clutch?) doesn't retract in time and when the engine catches there is a brief but annoying sharp grinding noise.
This suggests that the starter drive is sticking sometimes.

Quote:
Additionally, the cold starts this winter have sounded like the battery has been under more load than I'd expect at these temps (at or below freezing in the morning). There's this brief pause when you first turn the key where for a second I'm not sure whether the engine will turn or not. Almost like the dull hum of an electric motor under too heavy of a load.
This could indicate a starter problem, but it could also be due to the battery being a bit low -- which could be the effect of excessive drain overnight.

Quote:
Originally Posted by QuickSilver View Post
Parked the car for the weekend and this morning came out to find the car completely dead. Even the LCD clock was dead. Battery completely drained.
And this could be the effect of excessive drain over a weekend. However, there is no way on God's green earth that this could be caused by a starter* or by an alternator not charging.

Quote:
You may very well be right about the starter being the possible cause.
For the battery going dead? No, that cannot be right.

*Unless the starter is stuck engaged, in which case it would make hellacious noise while the engine was running and would be cranking the engine when the car was turned off. You'd know if this was going on.
#19
Old 01-14-2014, 10:55 AM
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Well, whatever the cause, I'll provide an update when I have one. I had a late day at the office yesterday and an early morning today, so I've not been able to do a damn thing about the car. If time permits, I'll boost start it tomorrow morning with my other car and get it over to my local shop. No matter what happens, the starter will probably need replacement. I was going to spend time screwing around with isolating the possible parasitic draw but knowing that there are other issues that will surely need attention, I'm just going to let the experts with all the tools and equipped garage handle it.
#20
Old 02-05-2014, 07:09 AM
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Update:

Whelp.... Had the car in the shop for a week and a half. Interstate battery took the battery back to their shop for testing and the results came back negative for any faults. Meanwhile, the machanic tested the car for any parasitic draw every day (I have no reason to believe they would lie) and results came back negative as well; no draw detected. They handed me the keys and said, "Sorry Mr. QS, we can't find the fault and frankly we're baffled. Bring it back if it happens again."

Is there a way I can record the draw with an A-meter and save the value for me to at least be able to positively confirm the parasitic drain hypothesis?

Take it to another shop?

What say you, oh auto-mechanical mavins?
#21
Old 02-05-2014, 08:03 AM
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Quote:
Originally Posted by QuickSilver View Post
Update:

Whelp.... Had the car in the shop for a week and a half. Interstate battery took the battery back to their shop for testing and the results came back negative for any faults. Meanwhile, the machanic tested the car for any parasitic draw every day (I have no reason to believe they would lie) and results came back negative as well; no draw detected. They handed me the keys and said, "Sorry Mr. QS, we can't find the fault and frankly we're baffled. Bring it back if it happens again."

Is there a way I can record the draw with an A-meter and save the value for me to at least be able to positively confirm the parasitic drain hypothesis?

Take it to another shop?

What say you, oh auto-mechanical mavins?
Taking it to another shop could be a good option to get a second opinion.

As I mentioned earlier, consider getting an under-hood battery disconnect switch.

http://harborfreight.com/battery...tch-97853.html
#22
Old 02-05-2014, 08:40 AM
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Car wonks: Identifying Parasitic Drain.

I assume you lock the car when you park it. If so ask the shop if they tested for a draw with the car locked.
I once had my ass handed to me with a draw I could not find. It turned out the lock relay was bad and would stick on. If the car was unlocked no problem and since we leave cars in the shop unlocked... Get the picture?
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Last edited by Rick; 02-05-2014 at 08:40 AM.
#23
Old 02-05-2014, 08:51 AM
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Quote:
Originally Posted by Rick View Post
It turned out the lock relay was bad and would stick on. If the car was unlocked no problem and since we leave cars in the shop unlocked... Get the picture?
Damn. I wish I had thought of this. After a recent crash, my Yukon developed an intermittent draw that was never found. I tried, the dealer tried, a specialty electrical shop tried. For weeks, and we couldn't track it down.

I finally sold the truck and got a new one. I'm just saying, it's one option!
#24
Old 02-05-2014, 09:10 AM
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Originally Posted by JerrySTL View Post
As I mentioned earlier, consider getting an under-hood battery disconnect switch.
I took note of this ealier and saved the link. It's an option of second to last resort.

Quote:
Originally Posted by Rick View Post
I assume you lock the car when you park it. If so ask the shop if they tested for a draw with the car locked.....Get the picture?
Foolishly I assumed they would test for this since that's how I found the car dead in the first place. I suppose I should learn by now what happens when one assumes. That's why I'm wanting to find out if I can test it myself in that condition but I don't want to stand over the meter for hours and hours.

Quote:
Originally Posted by ducati View Post
I finally sold the truck and got a new one. I'm just saying, it's one option!
...and there it is - the option of last resort.

Last edited by QuickSilver; 02-05-2014 at 09:11 AM.
#25
Old 02-05-2014, 12:18 PM
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Quote:
Originally Posted by QuickSilver View Post
Is there a way I can record the draw with an A-meter and save the value for me to at least be able to positively confirm the parasitic drain hypothesis?
Yes, with the right equipment.* But I doubt this will be helpful.
Quote:
Originally Posted by Rick View Post
...ask the shop if they tested for a draw with the car locked.
Quote:
Originally Posted by QuickSilver View Post
Foolishly I assumed they would test for this since that's how I found the car dead in the first place....That's why I'm wanting to find out if I can test it myself in that condition but I don't want to stand over the meter for hours and hours.
It sounds like you're speculating that the draw might not appear right away but could pop up after it sat for a while. I won't say that's impossible, but I think it's extremely unlikely. I've never heard of such a case. The matter here is the possibility that the draw exists in a condition that wasn't part of the testing. If a draw is present only with the car locked, it should show up right away if tested for when the car is locked.

What is probably more of a concern is that many cars will have a significant draw for some time after the key is removed, due to modules that don't shut down right away as part of normal operation. It can take from several minutes to a couple of hours for all the modules to go into their "sleep" mode, which is when a meaningful test for an abnormal draw can be performed. Whether this applies to your car I don't know.

I can't think of anything that would cause the battery to go dead other than an abnormal draw or a faulty battery. If a battery fails a given test, that proves that it's bad, but if it passes that doesn't necessarily prove that it's good. Did Interstate have the battery long enough to see if it lost its charge prematurely over a several day period? If not, perhaps the battery is still a suspect. If so, I'd think there has to be a draw that hasn't been caught in the act yet, and checking for that with the vehicle locked is the logical next step.

If there's any question that the shop is doing the testing properly, going to another shop would make sense.

*To get a record of an electrical value over a long period of time requires a multimeter with a MIN/MAX record function or an oscilloscope that can be set to a slow enough time setting so it could show several hours on its display. Any auto shutoff feature would have to be turned off.
#26
Old 02-05-2014, 01:38 PM
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A DMM with RS-232 output is perfect for long-term low sample rate data logging.
Something like this.
Of course, you need to dedicate a computer to the task of recording the data...
#27
Old 02-05-2014, 01:51 PM
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When you said the car "hesitates" when starting on a cold morning, do you mean it doesn't crank immediately, doesn't crank very fast, or cranks but doesn't fire?

One of the many common 90's VW electrical gremlins was sticky ignition switches. On VW's the equivalent of the "ACC" position is simply sticking the key in the ignition. Sometimes the switch gets stuck and the things that are powered in that position will stay powered after you pull the key out. The most obvious indication of this is that your radio will stay on when you pull they key out, but you say you're anal about switching it off before turning the engine off, so you might not notice it. I could definitely see that being an intermittent problem and possibly one that doesn't reproduce during warm weather or when parked in a nice toasty garage. I'd especially eye that with suspicion if your cold weather starting problem could possibly be related to an ignition switch.

Also you don't happen to have an aftermarket radio, do you? That can also lead to some problems with the funky VW radio wiring set up.
#28
Old 02-05-2014, 01:57 PM
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Does the meter come with the monitoring software, beowulff?

Also, the battery is not above suspicion. This is the second battery in as many years. Interstate replaced the first one a year ago. It was a year old and dead just like this one. A bench test revealed the first one was faulty. This one is a year old now and found dead like the first. Bench tests did not reveal a fault but as you say, Gary T, doesn't mean it's not another bad battery. What dumb fucking luck it would be if it's another dud. That's why I suspect a random drain. But you'd think it would take less than a year to drain the battery if it was a drain, right?

I'm second guessing this all over the place.
#29
Old 02-05-2014, 02:08 PM
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Quote:
Originally Posted by GreasyJack View Post
When you said the car "hesitates" when starting on a cold morning, do you mean it doesn't crank immediately, doesn't crank very fast, or cranks but doesn't fire?

One of the many common 90's VW electrical gremlins was sticky ignition switches. On VW's the equivalent of the "ACC" position is simply sticking the key in the ignition. Sometimes the switch gets stuck and the things that are powered in that position will stay powered after you pull the key out. The most obvious indication of this is that your radio will stay on when you pull they key out, but you say you're anal about switching it off before turning the engine off, so you might not notice it. I could definitely see that being an intermittent problem and possibly one that doesn't reproduce during warm weather or when parked in a nice toasty garage. I'd especially eye that with suspicion if your cold weather starting problem could possibly be related to an ignition switch.

Also you don't happen to have an aftermarket radio, do you? That can also lead to some problems with the funky VW radio wiring set up.
By "hesitates" I mean the typical weak battery symptoms. Like the starter motor is turning through thick molasses. You know, that - woo-woo-woo-catch sound. Not the cranking like a bastard but doesn't want to start deal.

It's a 2000 model so I'm not sure the 90's gremlins apply here.

No after market electronics involved. Everything is stock. The starter motor is original. It does have a rare issue with a sharp grind once the engine has caught. Like the solenoid (?) doesn't pull the start gear back in time and it grinds as the engine takes over. That happens once in 10-20 starts and last about a second. I have no idea if it could be a contributing factor here.

I'm retarded about shutting off all the electrics before turning the car off, as a habit: fan, radio, lights. And I never use the vanity mirror.
#30
Old 02-05-2014, 02:13 PM
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Quote:
Originally Posted by QuickSilver View Post
But you'd think it would take less than a year to drain the battery if it was a drain, right?
Sure, it seems to only take two or three days, but the the drain may have just started recently.
#31
Old 02-05-2014, 02:24 PM
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Originally Posted by Gary T View Post
Sure, it seems to only take two or three days, but the the drain may have just started recently.
It's my commuter car. It sits regularly for 2-3 days on weekends without being started/driven. Took a year to drain the first new battery. Another year to drain the second new battery.

If the draw is that sporadic, it'll be a bastard to find and resolve.
#32
Old 02-05-2014, 02:37 PM
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Originally Posted by QuickSilver View Post
Does the meter come with the monitoring software, beowulff?
If you buy the meter new, yes.
But, even if you don't get the software with the meter, they generally just spew out readings on the serial port, and you can use something like Hyperterminal (or Zterm on the Mac) to capture the data.

Last edited by beowulff; 02-05-2014 at 02:38 PM.
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