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  1. #1
    DJ '99 328iC
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    Fuel Door Lock Actuator

    My actuator only functions in the unlock direction. Yet when I remove it and apply battery voltage direct, it operates in both directions when switching the leads. Looking at the wiring diagram, it seems to me that if it works in either direction the integrity of the wiring is verified. I can't tell by the print whether or not it receives full voltage from the control module. My assumption at this point is that when it is installed there isn't enough oomph to drive this weakened actuator in the lock direction vs a direct hook up to the battery. Any thoughts before I purchase a new one?


  2. #2
    ADS
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    What I get from this is deteriorated wire

    There should be very little drop across good wiring - such that it shouldn't be different than hooking directly to the battery.


  3. #3
    DJ '99 328iC
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    Wouldn't that affect it in either direction....

    lock or unlock? Whether the deteriorated wire was power or a ground, the voltage drop would be divided, right? And which wire is power and which one is ground depends on whether you're locking or unlocking. Or am I misunderstanding this circuit?

  4. #4
    ADS
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    Rereading your init post

    you may be right - still not completely clear.
    Without knowing how the wiring runs (no diagram) I'm still not clear.

    Also, when you hook it to battery, do you mean you're jumpering it with another wire, or removing it and hooking it up directly to the battery?
    If it works removed - meaning it doesn't have to deliver the force to the mechanism like when it's installed, then you're probably right, but I'd check a few things based on the behavior of my right rear actuator, which was flaky for about a year but has now been working well for a year.
    1. check the voltage from the wire while it's installed if possible. You could run a really small wire - like a single phone wire strand - into the connector then check voltage when you actuate; probably a pulse and won't be too accurate but worth a check.
    2. this one is key - check the mechanism, clean and lube it. Maybe it's taking more force in the lock direction.
    3. clean the contacts and put some dielectric grease - or better, stabilant 22, but that stuff is expensive on the contacts. Try NAPA for stabilant22. BMW recommends it especially for E36 era cars as they cheaped out on the contacts of the DME and relays. Point is to get the connection clean and as good as possible.
    4. I can't tell w/o diagram if they've center-tapped a coil and then apply voltage to either one side or the other(3 wires), or use relays to switch the polarity with only 2 wires. If 3 wires, determine which is the center tap wire, then check the ohms from the center/ground wire to each of the other, should be about the same. Higher ohms will normally mean that side/direction would have less force *IF* the coils are of equal windings for up and down. If two wires, this won't apply as well, but you could check the ohms on this one and one on the other door for comparison; in this case if the failing one is higher-again, an indication it would deliver less force.
    If it's two wires (probably based on your last post), if one wire was "weak" or partially broken inside the insulation, you're right, should be a problem in either direction. However, if it were skinned insulation and the wire is partially but barely touching metal, that may not affect that wire when it acts as a ground, but could when it is supposed to apply voltage.
    On E46's, the control circuit is often the problem; there are write-ups about this if you search, but on E36's, usually it is the actuator - but I'd do some checking since most places won't allow electrical part return.

    Good luck.
    ADS

  5. #5
    DJ '99 328iC
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    Re: Rereading your init post

    I'll come back to this later when it becomes a higher priority, like someone swiping my gascap! I read a message on a 5 series board about the gas door being tied into the double lock feature with the key. Thought I'd check it out. One last check with the remote and it worked in both directions! Curious. Checked operation with key, works fine. This being done with the actuator hanging on the connector. As a side note, I didn't notice a double lock feature with the key like I have with my '92 735. So I put it all together after cleaning the connector with 2-26 and spraying the actuating rod and bellows with silicone spray. Doesn't work- remote or key.
    So with a CE light to deal with, a seat back gear to replace and a final stage unit to replace for an inop blower, this is over for now. To answer your question, I verified with a direct hookup to the battery and being a 2 wire setup, I believe it just swaps power and ground. Although there's no telling whats actually happening inside the control unit.

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