Possible low Amps clamp fault

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Possible low Amps clamp fault

Postby mikeevans » Fri Dec 12, 2014 6:14 pm

I have recently had a problem whilst trying to diagnose a parasitic battery drain on a 2008 Freelander 2. This is proving to be difficult to trace and I have had the added difficulty of having a possible faulty Low Amps clamp. The Auto kit comes with 2 lo Amps clamps. I have only ever used one clamp ,approximately 10 times. When using this clamp to try and diagnose the drain I was getting inconsistent readings .Having originally zeroing the clamp the battery drain was monitered and it would eventually show a drain of about - (minus)70mAmps . To me with my limited knowledge I couldn't understand how it was possible for the reading to go below zero which is when I decided to try the other amps clamp which came in the kit. Using the 2nd clamp gave me a more plausible reading with a "shut down" drain of about 150 mAmps. I therefor suspect that the 1st amp clamp is faulty. If so, is it usual for a clamp to develop a fault having had so little use ? I would expect such a clamp to give many years of service espcially from the company that I regard as being the "Rolls Royce " in this field. If it is not faulty, can someone explain the negative reading I was getting with this clamp. I managed to record and save the reading and I will try and upload it to the forum when I work out how as I would appreciate some help in trying to locate the battery drain
Mike
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Re: Possible low Amps clamp fault

Postby Robski » Fri Dec 12, 2014 7:45 pm

with a "shut down" drain of about 150 mAmps

How long did you give it to 'sleep' ?

as I would appreciate some help in trying to locate the battery drain


Is that as far as you got or did you volt drop anything, or are you wanting to be told how to further progress ?

The amps clamp will 'drift' & will need zeroing at intervals. This doesn't mean I'm saying your first clamp is not at fault.
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Re: Possible low Amps clamp fault

Postby KimAndersen » Sat Dec 13, 2014 11:08 am

Hi

May I lead your attention to this thread, https://www.picoauto.com/support/topic9482.html where I and others are discussing different options in locating parasitic current drain from the battery.

Regards
Kim
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Re: Possible low Amps clamp fault

Postby mikeevans » Sat Dec 13, 2014 3:39 pm

Hi Thanks for your reply.The shut down period went as follows.
Locked car-
After 25 secs. drain dropped to 1.1A
After 90 secs. drain dropped to 900mA
Add 8 mins drain dropped to 203mA
Add 19 mins drain increased to 1.49A
Add 20 secs. drain dropped to 760mA
Add 18 mins drain dropped to 125mA
This is where it stayed for about 1/2 an hour at which point I stopped the test.
The car was not disturbed in any way during this period and I can't explain the increase during this period.
Each fuse was removed one at a time and also relays removed with no reduction in drain. Obviously when alarm fuse was removed alarm went off and had to rerun shutdown period again.
Disconnected the easy bits, Audio, terrain switch with no reduction in drain.
Car has now been returned to customer but will be back with me soon to try and fix.
I understand that the body control unit ( which also incorporates the fuse box) can sometimes be the culprit and I may end up spending many hours stripping and disconnecting components without being able to identify a faulty component. Before starting , I found a company who assured me that they would be able to test the body ECU and according to them they can find no fault with it. I'm not convinced that that such a test is reliable and still suspect that there may be an issue with that component. If anyone has any previous experience of Freelander 2 or any advice on how to proceed with the diagnosis I will be most grateful. The drain when shut down is inconsistent, sometimes 25mA , other times, 150/ 200 mA. I think that the acceptable drain for this vehicle is 30mA max.
Mike
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Re: Possible low Amps clamp fault

Postby mikeevans » Sat Dec 13, 2014 3:40 pm

Hi Thanks for your reply.The shut down period went as follows.
Locked car-
After 25 secs. drain dropped to 1.1A
After 90 secs. drain dropped to 900mA
Add 8 mins drain dropped to 203mA
Add 19 mins drain increased to 1.49A
Add 20 secs. drain dropped to 760mA
Add 18 mins drain dropped to 125mA
This is where it stayed for about 1/2 an hour at which point I stopped the test.
The car was not disturbed in any way during this period and I can't explain the increase during this period.
Each fuse was removed one at a time and also relays removed with no reduction in drain. Obviously when alarm fuse was removed alarm went off and had to rerun shutdown period again.
Disconnected the easy bits, Audio, terrain switch with no reduction in drain.
Car has now been returned to customer but will be back with me soon to try and fix.
I understand that the body control unit ( which also incorporates the fuse box) can sometimes be the culprit and I may end up spending many hours stripping and disconnecting components without being able to identify a faulty component. Before starting , I found a company who assured me that they would be able to test the body ECU and according to them they can find no fault with it. I'm not convinced that that such a test is reliable and still suspect that there may be an issue with that component. If anyone has any previous experience of Freelander 2 or any advice on how to proceed with the diagnosis I will be most grateful. The drain when shut down is inconsistent, sometimes 25mA , other times, 150/ 200 mA. I think that the acceptable drain for this vehicle is 30mA max.
Mike
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Re: Possible low Amps clamp fault

Postby KimAndersen » Sun Dec 14, 2014 11:43 am

Hello again !

I may have some information regarding the parasitic current drain you are having on this Freelander. The document I have uploaded here, is a copy/paste from another Landrover document that I found on the web.

Here is a quote from the document:

" Many modules take considerable time to power down. Each time a fuse is removed and re-fitted, the quiescent drain current may take an extented period of time to return to normal (typically up to 45 minutes) "

Judge for yourself whether this is useful information in relation to your problem ! :wink:

Landrover_Quiescent_Current_Testing.pdf
(1.36 MiB) Downloaded 894 times


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Kim
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Re: Possible low Amps clamp fault

Postby arjen » Sun Dec 14, 2014 4:33 pm

Instead of pulling fuses to find the problem you can measure voltage drop over the fuses, this is a lot faster because you don 't wake up modules etc.
When there is no current flow trough a circuit, the voltage over the fuse is zero. When there is a current, there wil be a voltage drop over the fuse. You can measure that drop with the millivolts setting on your dmm.
I have a diagram where you can check how many voltage drop is how many current flow.
I wil upload it as soon as I can. You can probably find it on google too.
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Re: Possible low Amps clamp fault

Postby Steve Smith » Tue Dec 23, 2014 11:21 pm

Hello Mike and to all, thanks for your posts

Regarding the concern with your clamp, how is this going?

With regards to reverse flow of current into the battery rather than away, ( parasitic current) I have only seen this when either the clamp is installed incorrectly or dual vehicle batteries are installed and the batteries are equalising in charge level after engine off.

Can I ask Mike if the clamp has a good battery installed?

On another note for accurate low current measurements with accurate resolution it may be necessary to switch on your clamp and zero as normal, apply the clamp to measure the parasitic drain but zero again around 15 minutes into your measurement.

A characteristic of inductive current clamps is they have a tendency to " drift" from their zero point as a result of temperature or as a result of the environment they are operating. Periodic zeroing of the current clamp during prolonged use is good practice and allows you to confirm the current you are measuring is correct relative to " zero "

However having said all that, as mentioned in Kim's post above, please take time to read topic 9482.

Every post is packed full of information regarding parasitic measurements and a reason why you would NOT zero your current clamp for extended parasitic drain tests ( over 12 hours) !

If you have any concerns about the clamp or feel the accuracy is not as expected when compared to your other clamp could you email into support@picotech.com

If you can include a brief description and include this thread as a reference we can take a look for you and confirm the accuracy and any errors.

It would appear our Freelander is settling around 125 to 150 mA and this would be of concern but beware.

From my experience there has often been times when I could see this level of discharge for over 1 hour. This often occurred If the vehicle had been recovered with a discharged battery. (The battery would be recharged but fail the parasitic drain test)

The internal battery back up feature-built into the alarm siren would also discharge with the 12 V vehicle battery and would require recharging from the vehicle battery. This process could be seen in the parasitic measurement, and confirmed by disconnecting the alarm siren.

It would appear the more laden a vehicle with networks and nodes the more likely we see prolonged shutdown periods and parasitic current draw that pushes the limits.

As a general rule of thumb, if I can see less than 80 mA parasitic current drain for a sustained period ( no further activity) then this would suffice. ( keeping any SMART keys out of vehicle detection range)

Speaking to numerous manufacturers I will not comment on what a certain VM claimed was acceptable other than to say good luck if leaving your vehicle parked for 3 days!

I hope this helps. Take care. Steve
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Re: Possible low Amps clamp fault

Postby mikeevans » Mon Dec 29, 2014 10:33 pm

Thanks to everyone for the advice and information you have given me regarding the Freelander battery drain. I must confess that my knowledge of modern vehicle electronics is rather limited as my background as a motor vehicle mechanic goes back as far as the late 1970's where things were quite different then. I now operate a small car, 4x4 and ATV sales and repair business and from time to time encounter problems like the Freelander battery drain, which with my limited knowledge is proving to be very time consuming to diagnose. Historically I have used an autoelectrician to assist but because of the nature of some of these faults they are often reluctant to take the jobs on as they are usually less profitable than simpler jobs. As there appears to be no competant autoelectrician within a 25mile radius of me I decided that the best course of action was to purchase a picoscope and to attempt to learn how to deal with such faults myself. To return to the Freelander fault, the car has now been returned to the customer but is coming back to me sometime in January while the customer is away for about 7 weeks. Luckily he is very understanding and is keen to know what is the root cause.
It hadn't occured to me that I could perform voltage drop tests across fuses and this is one approach I will take when I next see the car. Pulling fuses has proven to be extremely frustrating due to systems waking up and then having to wait for full shutdown before the next check. My original query regarding the amps clamp should possibly be ignored as I was unaware that readings could drift and I should have fitted a new battery before starting.
Despite the difficulties I have encountered I find the subject very interesting and I am determined to get to the bottom of this problem hopefully with the help and guidance of the forum.
Thanks again guys , Mike
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