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Old 05-01-2008, 10:13 AM   #1
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What is causing this drain?

Twice now over the holidays I've had to call out MobiloLife for a flat battery (new one year ago).

Something is draining the battery but what? I have three possibilities:
  1. UHI Kit, retrofitted by myself with expert advice and the least likely as fitted for two months now.
  2. TV Tuner - as the car was pre-wired, with the exception of the amplifiers, unlikely as it should have been plug and play.
  3. Third party DVD/MP3 player. Most likely as just fitted, but by a professional installer. Unit goes off with ignition. One possibility was the USB input, a memory stick in there may have been draining when off but no light was showing from the stick when ignition off.
Ideas please. I've disabled the DVD player until I can get it checked and I can see it is the most likely but why? If the unit powers down when the ignition is off there should be no drain, right?
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Old 05-01-2008, 10:16 AM   #2
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The max current allowable is 38m/a when the car is locked.

This can only be checked by inserting an ammeter without breaking the circuit so that the path of the leak is not broken
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Old 05-01-2008, 10:36 AM   #3
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MobiloLife checked by some device that encircled the live feed from the battery. They said it should show no more that 0.08 amps. The closed the boot lock and locked the car to fool the car into thinking it was fully closed and shut down. It got down to about 0.18-0.20 after around 15 minutes.

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Old 05-01-2008, 10:43 AM   #4
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Quote:
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MobiloLife checked by some device that encircled the live feed from the battery. They said it should show no more that 0.08 amps. The closed the boot lock and locked the car to fool the car into thniking it was fully closed and shut down. It got down to about 0.18-0.20 after around 15 minutes.
I hope you mean 0.018 -0.020 if not then something is drawing too much.

The device they used was a clamp meter

The figure of 0.080 is an outside max when they have problem cars but 0.038 is the correct max when perfect and locked
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Old 05-01-2008, 10:47 AM   #5
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They said about a quarter of an amp. So something is draining it.

Last edited by amwebby; 05-01-2008 at 10:52 AM.
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Old 05-01-2008, 10:59 AM   #6
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They said about a quarter of an amp. So something is draining it.
The Comand is one of the biggest reasons,it is quite simple to withdraw the fuse for this and pop an ammeter over the two contacts, this will cover all items on that circuit.

Another is the OCP

I have the Comand problem, so I modified the shut down circuit
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Old 05-01-2008, 11:02 AM   #7
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The MobiloLife technician mentioned COMAND as the most likely culprit. Why should it suddenly start doing this though, unless adding the TV caused it?
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Old 05-01-2008, 11:03 AM   #8
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I don't know anything about an SL but just happened to read about an incorrect relay installed on the additional fan, causing an additional current drain of 0.2 amps, this figure just goes with the figures measured from the car.

I believe my clamp meter would be able to detect this current level without uninstalling the battery cable, would just need to remove the fuse for the additional fan.
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Old 05-01-2008, 11:05 AM   #9
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Quote:
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The MobiloLife technician mentioned COMAND as the most likely culprit. Why should it suddenly start doing this though, unless adding the TV caused it?
Again, don't know but there were several posts on other cars about the equipment on the CAN, the same one Comand would be using and any of those could cause Comand not going to sleep (of course an issue at the Comand unit itself too).

But taking fuses out one by one should help diagnosing (although the one taken off might help the faulty one go to sleep).
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Old 05-01-2008, 11:06 AM   #10
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I don't know anything about an SL but just happened to read about an incorrect relay installed on the additional fan, causing an additional current drain of 0.2 amps, this figure just goes with the figures measured from the car.

I believe my clamp meter would be able to detect this current level without uninstalling the battery cable, would just need to remove the fuse for the additional fan.

I think that this fan is the OCP one that affects the Comand
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Old 05-01-2008, 11:07 AM   #11
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I have the Comand problem, so I modified the shut down circuit
Don't they have any SW update solution? If it is HW, I would expect a new device as it is a design flaw?
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Old 05-01-2008, 11:09 AM   #12
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I think that this fan is the OCP one that affects the Comand
I guess that fan could be an issue or the OCP panel itself but the document I was reading was really about the additional fan, covered by F42 to on the right fuse and relay box (I just happened to read about it, don't have any experience).
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Old 05-01-2008, 11:10 AM   #13
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That fits in with my theory, that the feed to the DVD unit is somehow at fault. I've withdrawn the power supply to the unit at the back but sadly I don't own a clamp meter.
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Old 05-01-2008, 11:11 AM   #14
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Don't they have any SW update solution? If it is HW, I would expect a new device as it is a design flaw?
Up till recently there has been no one that would repair these things, but there are firms now that are starting to do work on them.

MB have been quite happily taking a few grand for replacements.
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Old 05-01-2008, 11:16 AM   #15
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That fits in with my theory, that the feed to the DVD unit is somehow at fault. I've withdrawn the power supply to the unit at the back but sadly I don't own a clamp meter.
Before I modified mine the CD changer would keep trying to load until the battery cut off when it got down to 11.7 volt.

CPC have a meter with a fuse plug on the leads, and you just plug this in in place of the fuse to get an instant read out of up to 20 amps, they cost about 6 + VAT.

A clamp meter would cost around 300 to measure DC down to 20m/a
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