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Intermittent turn signal failure


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Wise Ones of the BMW Tribe,


Please come forth with your advice on how to diagnose an intermittent (although getting more and more frequent) light problem. According to the brain, my right front turn signal bulb is burnt out. This of course is not the case and resetting the computer returns all to normal function (for a random amount of time). The socket appears to be making contact and, the connectors are on tight Other than that, i have not done any more investigation.


In my vast tool kit is a simple volt/ohm meter and not much else. So, armed with that, i look forward to your expert advice.


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Evening Rick


That could be a tough nut to crack without some elimination.


I guess the first thing to try is a new bulb (or swap it with the other side). Maybe there is a resistance issue with the bulb making the current draw low enough that ZFE thinks it isn’t working.


If the bulb doesn’t help then look for an intermittent ground problem (a ground going open or high resistance could change the current draw enough to make the ZFE think the bulb is out.


Otherwise you might have to go back to the beginning of both the left & right side front turn signal circuits and measure the circuit resistances to see if the problem side is higher.


If the problem is in the ZFE itself I have no idea how you will isolate and find that without swapping in a known-good properly working module.



Added: Another thought, maybe put the emergency flashers on for while then watch the front bulbs. See if the problematic side flashes at a constant brightness equal to the other side.

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I have had the same problem with a car.


Changed bulb, still said it was burned out.


Ended up having to change the sockets.

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