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Old 08-19-2013, 03:43 AM
jdd jdd is offline
Join Date: May 2011
Location: Melbourne, Australia
Posts: 71
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I have checked both the cold and hot monitoring lamp check signals on my own X5, with some interesting results.
For the benefit of those non-believers on this forum I performed this test on the angle eyes circuit, although the results are likely to be the same for a number of other light circuits.

During hot monitoring the bulbs are pulsed once every 80mSec with a clean ‘square wave’ from 12V to zero and back to 12V, this pulse is about 5mSec in duration. The hot monitoring phase starts more or less straight after the cold monitoring phase and is done so that if a bulb fails while you’re out driving around it will bring up a warning on the dash.

During the cold monitoring phase I found both positive and negative pulses.
While the positive going pulses should not cause any issues, the negative going ones are large enough to potentially damage a LED.
As I have mentioned previously, the issue is NOT the fact that the LED’s are pulsed, it is the fact that during the cold monitoring lamp check there are negative pulses generated which LED’s are sensitive to.

A simple solution for those who don’t have the ability to turn this off would be to splice a diode of suitable amperage (eg IN5401 or similar) in series with the angle eye circuit with the grey wire connected to the anode and the cathode connected to the positive side of the LED.

Last edited by jdd; 08-19-2013 at 03:44 AM. Reason: removed references to forum troll
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