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De-activated black box draining battery


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My son’s 2009 Fiesta had a battery drain that I traced to the Telematics Black Box that was fitted as part of his RAC Insurance three years ago.  Having read some of the related threads on this and other forums, I thought I’d write up my experience.

I disconnected the earth lead of the battery and put a cheapo multimeter set to 10A DC between the earth terminal of the battery and the earth lead.  The car was locked with everything off, and I was getting about 1A.  That would explain why the (newish) battery was going flat in a few days.

I pulled out the fuses in the engine bay fuse box one-by-one, and found Fuse 5 marked BATT was the culprit.  However, that is the feed for the fuse box in the passenger compartment.

Opening the car increased the current drawn to 1.5A, but that includes all the interior lights and instrument panel etc so hardly surprising.  Out with the glove box (squeeze the sides and out it pops) and there’s the fuse box.

Repeat the exercise of pulling out individual fuses, noting that Fuses 20 and 21 run the clock, audio system, displays, etc so they will be drawing some current anyway.  I found that pulling Fuse 19 marked OBD made a significant difference.  That is the datalink connector used for diagnostics by garages (I think OBD stands for On-Board Diagnosis but I could be wrong)

Pulling Fuse 19 and then locking the car caused the current to drop to 0.06A.  It takes a few seconds to get there while everything shuts down.

The OBD connector is under the steering wheel.  To get to it, open that little storage bin thing under the switch for the headlights, undo the one screw that holds it in, pull gently and the bin pops out.  The OBD connector is white and, in my son’s car was connected to the Telematics black box that had been tie-wrapped to some nearby structure.  I disconnected it, put Fuse 19 back in, locked the car and watched the current drop to 60mA again.  Job done!

Some notes:

1.  My son’s insurance no longer requires a black box, don’t do this unless that’s the case as you will invalidate the insurance.

2.  Not all black boxes are wired to the OBD port, but this one was.  It just needs a constant 12V so other black boxes are wired to the fuse box itself or even directly to the battery.

3. The black box caused no problem for over two years so it only started draining the battery after he changed his insurance, or it got older.  As the black box contains a battery itself, I suspect that, like your mobile phone battery, they get less and less efficient over the years, draw more and more current, and that was the cause.

4.  Deactivated black boxes are still working - they are just no longer monitored.  Big Brother may no longer be watching you but he could if he wanted to!

5.  The RAC suggested getting the black box removed at the next service when my son asked.  Definitely worth getting done if you don’t fancy doing it yourself.

 

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