Measuring Parasitic Draw

I got a used Fluke 365 clamp meter cheap and am wondering if the range is right for measuring parasitic current draw. It is stated that it will measure as low as .1 amp (100 milliamp) but I guess it will round up to 100 milliamp from as low as 50 milliamp.

If this isn't a good tool for my intended purpose, if not, what range of clamp meter would be adequate? I also have a fluke 112 which I'm assuming would be good for measuring across fuses.

disregard my reply. misread your initial post...

Where are you trying to measure current, at the battery?
The recommended method is to measure voltage drops across fuses as detailed in this TSB: http://pics.tdiclub.com/data/500/TSB_27_08_04_Matrix.pdf


You also have to make sure the car "goes to sleep" before measuring. This means waiting several minutes after locking the car. If the hood is open you should unplug the hood open sensor and you have to fool any open door sensors or the car will not enter sleep mode.


Often parasitic current drains are because a controller won't go to sleep causing the CAN bus to not go to sleep. Often the fuse trick will tell you which controller is keeping things awake. A VCDS scan can sometimes help, but you have probably already tried that.



Have Fun!


Don

Thanks for the link. I had it saved somewhere but couldn't find it.The only place you use a clamp meter (step 2) is on the battery cable to make sure the car goes into sleep mode. So really the clamp meter is more of a Q&D to make sure the car goes to sleep before you start measuring at the fuses, so really, it's not needed so much, anyway.

The 365 clamp meter doesn't measure acutely below 100 milliamp so it would not be suitable for verifying the car is in sleep mode, so back it goes to the pawn shop.

I don't actually have a problem right now. Just wanting to understand how to use the 2 Flukes I got for dirt cheap. It looks like with the Fluke 112 I'm all set for trouble shooting for parasitic draw if I ever need to.

Years ago (2012) I was chasing a problem and I actually bought one of these: https://smile.amazon.com/ESI-695-Amps-Current-Probe/dp/B000FN4IUK/ref=sr_1_2?s=automotive&ie=UTF8&qid=1529121216&sr=1-2&keywords=es695+80+amp+dc%2Fac+low+current+probe


It is a clamp-on low current probe that will actually measure milliAmps.


Have Fun!


Don


P.S. It was cheaper when I bought it in 2012.

JSWTDI09 said:

Years ago (2012) I was chasing a problem and I actually bought one of these: https://smile.amazon.com/ESI-695-Amps-Current-Probe/dp/B000FN4IUK/ref=sr_1_2?s=automotive&ie=UTF8&qid=1529121216&sr=1-2&keywords=es695+80+amp+dc%2Fac+low+current+probe


It is a clamp-on low current probe that will actually measure milliAmps.


Have Fun!


Don


P.S. It was cheaper when I bought it in 2012.

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Thanx. looks like if you get stuck on something, it certainly could save the day....................

VW's official acceptable threshhold is 0.030 A / 30 milliamp. So yes, you will have to get something that reads less than that.

You will also have to unplug the hood switch, so the car recognizes as it being closed. I also recommend leaving the driver's door open but closing the latch so the computers recognize the door as being closed, even though it's not.

THEN go ahead and measure your draw. It will take a couple minutes for the control modules to go to sleep on a mk5. Mk4 and earlier are nearly instant, the mk5 and newer more computerized and networked cars do take a few minutes though for sure.

Mk4s often get close to 0.010 A when everything is asleep. Your mk5 will draw more than that, but anything under 0.030 A is good.

I second what Matt said.

On the A5s, the most common sources of phantom drains are from the door latches and the crappy Delphi radios. However door latch issues can also be confused with door harness issues. By now, anyone with a pre-2008 A5 should be considering installing the updated door harnesses... starting with the driver's door (obviously). They are not all that expensive, and not all the hard to do. I do these all the time. I have two here today.

The A5s are especially persnickety about the door latches, as they have no way to MANUALLY lock the doors aside from the driver's door. Since there is no lock knobs anymore. So if you have a flaky door latch, that will not lock... then you cannot lock your car. If you do, the CCM will quietly wait for that last door to lock, and it will kill the battery. I fix probably 20+ of these cars a year due to this.

This is VW's way of doing it. http://pics.tdiclub.com/data/500/TSB..._04_Matrix.pdf

I thought Fluke made pretty good meters, there should be a range setting to give you the correct range.

BobnOH said:

This is VW's way of doing it. http://pics.tdiclub.com/data/500/TSB..._04_Matrix.pdf

I thought Fluke made pretty good meters, there should be a range setting to give you the correct range.

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They certainly are probably the most durable and most accurate meters on the market, but are very expensive.

My thought is that if you don't switch on any loads, you wouldn't even need a clamp meter to measure current draw at the battery. It would just depend on your multimeter's Amp rating and how much the Amp measure function on the meter loads the circuit you are measuring.

• What is the normal current draw at the battery with everything switched off and the doors closed?
• When you arm the alarm, what does the current draw momentarily jump to?
• Would the meter load the circuit and prevent the car from going into sleep mode?

My Fluke 112 when measuring Amps:

• DC amp reading down to 1 milliamp (.001 Amp to 10 Amp range)
• 20 amp overload protection for 30 seconds (OL displayed)
• Meter display sleep Mode can be disabled (To not wake up a car in sleep mode)

Any thoughts on this? Just a WAG on my part, but I think direct reading instead of inductive reading parasitic draw at the battery might even work and be more acurate.

O.K., you don't want to read that thing, it's 40mA after 2 hours.
Recalling my very limited knowledge of electronics, pretty sure you need a shunt (clamp?) to measure amperage.

BobnOH said:

O.K., you don't want to read that thing, it's 40mA after 2 hours.
Recalling my very limited knowledge of electronics, pretty sure you need a shunt (clamp?) to measure amperage.

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Well, if using the meter in pass-through mode the meter itself would be a shunt.

BobnOH said:

O.K., you don't want to read that thing, it's 40mA after 2 hours.
Recalling my very limited knowledge of electronics, pretty sure you need a shunt (clamp?) to measure amperage.

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Put in series with a load, many multimeter's will directly read up to 10 Amps. The question would be, would an ammeter in series with the battery prevent the car from going to sleep? I'll probably just try it and see. I can't imagine the car draws enough load before it goes to sleep to blow the fuse in the meter.

I'm fairly certain that internal to the meter is a shunt and the meter fuse protects the leads and the shunt. The worst that could happen most likely is to turn on a load greater than the fuse is rated for blowing the 10 Amp fuse in the meter.

My Fluke 88 is rated for 10 A and momentarily can handle 20 A. I use it in series with the battery to accurately measure draws frequently enough. The computers don't know any better.

As you attempt to arm the car it will draw near that 10 A mark as the alarm horn sounds and lights blink, then quickly drop. Hasn't been an issue to measure in this manner... Just don't try to put it under a real load while hooked up in series.

Matt-98AHU said:

My Fluke 88 is rated for 10 A and momentarily can handle 20 A. I use it in series with the battery to accurately measure draws frequently enough. The computers don't know any better.
As you attempt to arm the car it will draw near that 10 A mark as the alarm horn sounds and lights blink, then quickly drop. Hasn't been an issue to measure in this manner... Just don't try to put it under a real load while hooked up in series.

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My Fluke 112 blinks the OL for a split second and then goes back to reading Amps when I arm the system. Probably the safest way to avoid current draw from the latches would be to arm the alarm first to lock all the latches, hook up the meter and arm once more to confirm the system is armed.

On my health car I did turn on the parking lights with the alarm not armed and it did display 7.29 Amps. Yup. So no extra load unless you want to take a chance and end up going down to your Fluke dealer and buy another $14 ($30 list) fuse. Right after arming the current flow displays 2.5 Amps. I agree were good to use just a multimeter instead of a clamp meter when measuring at the battery. When you did have a sick car what was the current flow right after arming?

Also to avoid waking up the car to check current draw at the fuses, connect a jumper in parallel with the meter before you take the meter out of the circuit.

JSWTDI09 said:

Where are you trying to measure current, at the battery?
The recommended method is to measure voltage drops across fuses as detailed in this TSB: http://pics.tdiclub.com/data/500/TSB_27_08_04_Matrix.pdf


You also have to make sure the car "goes to sleep" before measuring. This means waiting several minutes after locking the car. If the hood is open you should unplug the hood open sensor and you have to fool any open door sensors or the car will not enter sleep mode.


Often parasitic current drains are because a controller won't go to sleep causing the CAN bus to not go to sleep. Often the fuse trick will tell you which controller is keeping things awake. A VCDS scan can sometimes help, but you have probably already tried that.



Have Fun!


Don

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A common failure area is the wire harness to the driver's door. A broken wire in the door harness can cause the CAN bus to not go to sleep and create a parasitic battery drain. It seems a bit counter intuitive because a broken wire is normally not something you would be looking for when trying to chase down a parasitic battery drain.

n1das said:

A common failure area is the wire harness to the driver's door. A broken wire in the door harness can cause the CAN bus to not go to sleep and create a parasitic battery drain. It seems a bit counter intuitive because a broken wire is normally not something you would be looking for when trying to chase down a parasitic battery drain.

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I posted the thread more so to discuss the methodology for trouble shooting parasitic drain problems. The wiring harness, door latches and craptastic Delphi radios are pretty much known to be some of the root causes with the A5 platform.

Thanks for posting. Could you expand on your trouble shooting processes you have found to work on these digital cars? Messing round with this stuff, something I found interesting is that if you get an extremely low milliamp reading, it could be caused by poor electrical connections and grounds. Right to what you posted about wires.

I checked my health car today and abuot 4 milliamps in sleep mode, is that a normal number? Bad connection or bad ground maybe? IDK.

my process goes like so.

1. amp clamp the positive cable or negative cable. You need to do this and not just check voltage drop across fuses because you need to know if you even have a parasitic draw or not. Some training classes that I have been to have said 50 mA is the most you should have but I've seen cars that were ok with higher (150mA or so). The more technology on a car the more its going to draw normally.
2. If the car has an area that separates such as mk4 or mk5 underhood fuse box then you can amp clamp individual wires to see where the current is going.
3. Then check millivolt voltage drop across fuses. Of course let the car "go to sleep" and latch the door with a screwdriver so the dome light isn't on. It helps to check which fuses are powered up first because ones that are not can't have voltage drop. There is a chart on the power probe website (link below) that shows fuse size and voltage drop and amp draw (link below).

https://static1.squarespace.com/sta...79335/Fuse_Voltage_Drop_Chart_-_Mini_Fuse.pdf

But basically look at the fuses that have the highest voltage drop, id the fuses and look at a wiring schematic to see what is on those fuses.

here's my video on the subject. My video shows diagnostic process on a mk4 jetta and discusses every parasitic drain I've ever seen on a mk4 VW. I've seen the common problems on mk5 mentioned by others above as well.
https://www.youtube.com/watch?v=gNTmrwiPe6g&t=1s

there are of course other vidoe's on youtube regarding parasitic draw, including humblemechanic (vw related), Positive Lead Diagnostics (Vw related), South Main Auto and Pine Hollow auto diagnostics.

Thanks Richard, good stuff to have an understanding of. Some fantastic info.

I did find that I can use the 10 Amp function of my MM at the battery and if I jumper around it before taking it out of the circuit (series with the battery ground), the car doesn't wake up.

The puzzle for me is that when the car is asleep, it shows 3 or 4 Milliamps (.003 or .004 Amp) instead say 20 or 30 Milliamps. Internal resistance in the meter or my meter needs calibration perhaps?

Rattler, maybe it is below the range where the ammeter is at its best accuracy.

flee said:

Rattler, maybe it is below the range where the ammeter is at its best accuracy.

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I'll bet that probably it. The old rule of thumb. For best accuracy, you want your measurement to be mid range of the measuring device. Thanks for posting.