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Thread: '91 535 General Module (Ryan + BillR)?

  1. #1

    Default '91 535 General Module (Ryan + BillR)?

    Hi Guys-
    I still have the exact same symptoms as Ryan (no interior lights, no windows, locks, sunroof, wipers on high speed only, the illuminated window switch cluster flickers dimly...All Intermittantly! Usually not working more than working. Does not matter if it's the first start or throughout the day. I have swapped the GM-General Module without change
    My question is to verify which module controls these items.
    For instance, when the system is all 'working', and I pull the GM-General Module, the interior lights go off. I thought the RM-Relay Module is what affects all those items, not the GM. Perhaps I have been swapping the wrong module all along???
    I have checked all fuses and the fuseable link and all is good there. My car is a very rust/corrosion free machine, an Arizona native its' whole 13 year life, and all electrical connections are clean and shiny and they check OK with the OHM meter. Thanks for keeping the investigation going. This stinkin' PITA problem has got to go! Keith
    Keith in Scottsdale, AZ
    '91 535ia 220K Alpine/Parchment
    '89 735il 252K Cirrus/Parchment

    '00 740il 124K Oxford/Sand

  2. #2
    Join Date
    Jan 2004
    Posts
    1,342

    Default Ok Keith, let me try to make some statements ...

    General Module is the electronic, the brain, the decision maker, but it has no way to manage huge amps, so it drives the relays in the Relay module so they can switch on or off significant currents as consumed by interior lighting, wipers, locks, and windows. In an E34, these functions are not simple, as the car (GM) evaluate different conditions and thus operate various systems accordingly, for example, locking the car may also trigger the windows circuit to close all them together, leaving a door open will turn on interior lights but later on, in a timed manner, will be shut off to protect battery; wipers system evaluate your desire in the delayed operation so to match it automatically, also switches mode depending on car speed; locking system observe the operation of the locks to pop out if they fail locking, also check the status of drivers door, even more, if driver door have not open and closed after an engine turn off, the lock down locks mechanism and factory alarm will not engage. This functions require some intelligence to be carried out, and the electronics (though simple) will handle them, but again, the proper interface should be provided in order to convert low current signals, as handled by the electronics, in high power, as requested by the motors and bulbs.

    The General Module receives information from different switches around the car, mostly, as connect/donít connect to Battery +, these are fed by the small fuses in the module, also handles the coil of the different relays in the relay module, must of them fed by the 30A fuse F30.

    Iíve heard that the location of the Battery, right next to the General module, imposes a huge compromise in the connections it involves, as a matter of fact, I do always take good care of the tiny hose taking all the battery gases out of the car, My battery has never shown any sign of corrosion on the posts, nor the GM compartment has shown any sign of acid corrosion caused by the battery fumes or spills.

    I told Ryan to check proper grounding of the GM pin 2, just because if this ground is not OK, though the GM operates its internal switch (Electronic switch) to energize the Relay module relays coil, it closes its switch passing a ground that is not there, so GM is OK, Relay module is OK, but nothing works OK. You may swap as many GM and RM as you wish, nothing will change; unless the problem is in the socket contact and plug/unplug operations clean and solve it.

    My experience is that BMW electronics are pretty good (not infallible), not the connections though, If I were to debug a failure like this one, I would start unplugging the GM and RM and cleaning/spraying the plug contacts so to get better contact when plugged, also would check ground connections in the under seat area, and would verify presence (and in good voltage) of all Battery + and Ground feedings in the GM and RM connector sockets, even those that are received trough position sensing switches and operating switches. I understand this sound scary and that only professionals can do it, but believe me, a good voltmeter/ohmmeter, some spare copper wires, and a lot of time / patience, will do the magic.

    Please excuse my bad English, as it is not my mother's language.

    Javier

  3. #3
    Join Date
    Jan 2004
    Posts
    1,342

    Default Illuminated window switches. ..

    are fed by F47 trough the Power protection relay K15 (pin 6,2), trough the metering resistor in the GM (pin 4,5) and trough the Front console window switch. But again, if ground fails at GM, the Power protection relay open, turning of the power to the window switches.

    Javier

  4. #4
    Join Date
    Jan 2004
    Posts
    4,148

    Default Keith, Javier puts it much better than i could...

    1
    Quote Originally Posted by KeithW '91 535i
    Hi Guys-
    I still have the exact same symptoms as Ryan (no interior lights, no windows, locks, sunroof, wipers on high speed only, the illuminated window switch cluster flickers dimly...All Intermittantly! Usually not working more than working. Does not matter if it's the first start or throughout the day. I have swapped the GM-General Module without change
    My question is to verify which module controls these items.
    For instance, when the system is all 'working', and I pull the GM-General Module, the interior lights go off. I thought the RM-Relay Module is what affects all those items, not the GM. Perhaps I have been swapping the wrong module all along???
    I have checked all fuses and the fuseable link and all is good there. My car is a very rust/corrosion free machine, an Arizona native its' whole 13 year life, and all electrical connections are clean and shiny and they check OK with the OHM meter. Thanks for keeping the investigation going. This stinkin' PITA problem has got to go! Keith

  5. #5
    Join Date
    May 2004
    Location
    Japan
    Posts
    9,094

    Default nice write-up, Javier

    I will certainly use that when the next time someone is asking for the function of the GM.

    Thanks

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