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Thread: Low Beams Out; Most Likely Culprit?

  1. #1
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    Low Beams Out; Most Likely Culprit?

    The low-beam headlamps no longer work on our '87 325e. A year and a half ago I replaced the high-beam switch with a used one from a 633 (can you believe they used the identical part number?!?) for this same reason, but I have never replaced the headlamp switch.

    Are there any simple tests that I can perform to determine the problem? BTW, I tried replacing the low-beam relay with a a couple of known good ones, but no luck there.

    Jeff.
    1984 320i Baur TC2 5-Speed Opalgrün (Jeff's)
    1987 325e Sedan A/T Zinnoberrot (Dawn's)
    1984 633 CSi 5-speed Bronzit (Ours . . . if she says so)


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    richardodn's Avatar
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    It's more likely your high beam relay. The high beam relay is a changeover relay with 2 output legs; 87 and 87a. 87a is normally closed and supplies power to the low beam relay switch. When you switch the high beams on, it changes over to the 87 output, killing the low beam filament in the outboard lamps, and switching on the high beams and high beam filament in the outboard lamps. What happens when you turn your high beams on? Do the outboard lights come on? Are there any mods done to the lighting circuit?
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  3. #3
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    Thanks, Richard. I just replaced the high-beam relay with the correct relay (identical terminals and numbering to old relay) to try to address this problem. There are no mods to the lighting circuit whatsoever beyond the installation of Sylvania Halogen XtraVision sealed-beam headlamp bulbs and Sylvania Silver Star incandescent bulbs (silver bases) in all other bulb positions.
    1984 320i Baur TC2 5-Speed Opalgrün (Jeff's)
    1987 325e Sedan A/T Zinnoberrot (Dawn's)
    1984 633 CSi 5-speed Bronzit (Ours . . . if she says so)


  4. #4
    richardodn's Avatar
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    What happens when you turn your high beams on? Do the outboard ones light up?
    "Howdy, Folks!"

    1986 Delphin 528e - Roof rack equipped lumber hauler.
    1989 Zinnoberrot 325iX Sedan - I miss this car. (Deceased)
    1998 Avus Blau 328iC - Someone else's project now
    2008 Platinum-Beige X3 3.0si - Current project
    2012 Alpine White X3 xDrive35i - My new snowmobile.
    2020 Estoril Blue 440i xDrive cabrio - This car is a blast to drive.

  5. #5
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    Great question, Richard --- I didn't check for that!

    I will have to address that later; right now we are dealing with over 8" of snow here and the detached garage is not very accessible.

    Jeff
    1984 320i Baur TC2 5-Speed Opalgrün (Jeff's)
    1987 325e Sedan A/T Zinnoberrot (Dawn's)
    1984 633 CSi 5-speed Bronzit (Ours . . . if she says so)


  6. #6
    richardodn's Avatar
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    If they light up, at least you know the headlight ground is good. Remember there are 2 filaments in the outboard lamps; basically a combined low/high design. The 3 connections are low beam (from the relay), high beam (jumpered from the inboard high beams), and ground. A faulty ground would prevent either filament from lighting.

    Based on what you have tried, you're probably going to have to do diagnostics with a meter or test light. Your 87 is the early sealed beams and the diagrams are in the ETM on pages 6312-0 and -1.

    First check the ground as described.

    Pull fuses 13 and 14 (low beams). With ignition switch in run, light switch to headlights on, high beams to off, measure for voltage at the two fuse locations. Only one side of each will be hot so you may have to try both. If you get voltage, you have a chassis wiring problem. If you don't get voltage, the issue is with power supply, relays, or relay control. Inspect the fuses carefully before you put them back. If they're the old bullet style and they haven't been recently replaced, just replace them.

    If the previous test showed voltage at the fuses, you'll want to check for voltage at the headlights. With the same conditions as before except the fuses are installed, disconnect the headlight and measure for voltage on the yellow/white or yellow blue wires at the connector. If you have voltage and the ground is good, replace the headlight.

    Diagnosis of the rest of the circuit is a bit more involved, I'll write it up when I have some time.
    "Howdy, Folks!"

    1986 Delphin 528e - Roof rack equipped lumber hauler.
    1989 Zinnoberrot 325iX Sedan - I miss this car. (Deceased)
    1998 Avus Blau 328iC - Someone else's project now
    2008 Platinum-Beige X3 3.0si - Current project
    2012 Alpine White X3 xDrive35i - My new snowmobile.
    2020 Estoril Blue 440i xDrive cabrio - This car is a blast to drive.

  7. #7
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    Richard, sorry about the late reply; we have been dealing with 8.5 inches of snow since Sunday. Yes, both the low and high beams come on on "high beam". It will probably be a while before I can perform the other test you suggested.

    Jeff
    Last edited by BMWtyro; 01-22-2022 at 03:39 PM.
    1984 320i Baur TC2 5-Speed Opalgrün (Jeff's)
    1987 325e Sedan A/T Zinnoberrot (Dawn's)
    1984 633 CSi 5-speed Bronzit (Ours . . . if she says so)


  8. #8
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    One more (possibly stupid) question: since the all four of the headlamps light on high-beam circuit (and "flash" as well, which I failed to mention), how could both low-beam bulbs be bad?

    Jeff
    1984 320i Baur TC2 5-Speed Opalgrün (Jeff's)
    1987 325e Sedan A/T Zinnoberrot (Dawn's)
    1984 633 CSi 5-speed Bronzit (Ours . . . if she says so)


  9. #9
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    UPDATE:

    Driving the '87 325 yesterday, I noticed that the fog lamps (for which I always keep the button turned "on") come on ONLY WITH THE HIGH-BEAM SETTING and go off when switched to low-beam setting (which is the function that doesn't work).



    My recollection is that they are only supposed to be lit with the LOW-BEAMS, never the high beams.


    Hmm . . . could this be a clue . . ?

    1984 320i Baur TC2 5-Speed Opalgrün (Jeff's)
    1987 325e Sedan A/T Zinnoberrot (Dawn's)
    1984 633 CSi 5-speed Bronzit (Ours . . . if she says so)


  10. #10
    richardodn's Avatar
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    Quote Originally Posted by BMWtyro View Post
    One more (possibly stupid) question: since the all four of the headlamps light on high-beam circuit (and "flash" as well, which I failed to mention), how could both low-beam bulbs be bad?

    Jeff
    Remember the low beams lamps are actually 2 lamps in 1; one that lights with the low beam and one that lights with the high beam. The low beam filament can burn out but the high beam filament remains unscathed.

    Now when you add in the behavior of the high beams and the fogs, there's only one thing I can think of. I think you might have a bad G104 ground. That's the one from all the headlights. What would happen is that +12V is applied to both inboard and outboard high beam filaments. Normally current would flow through the filaments to ground which lights the lights. However without a ground connection, it's going to look for another path. There is one that runs through the outboard low beam filament, back to the control coil of the fog light relay (which would turn the fogs on), fog light switch, and finally light switch to ground. Turning off the fog light switch should eliminate that path and all the lights would go out. Alternately, they could just go really dim if the ground is only badly corroded and not quite gone.
    "Howdy, Folks!"

    1986 Delphin 528e - Roof rack equipped lumber hauler.
    1989 Zinnoberrot 325iX Sedan - I miss this car. (Deceased)
    1998 Avus Blau 328iC - Someone else's project now
    2008 Platinum-Beige X3 3.0si - Current project
    2012 Alpine White X3 xDrive35i - My new snowmobile.
    2020 Estoril Blue 440i xDrive cabrio - This car is a blast to drive.

  11. #11
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    Thanks, Richard. I did, of course, turn off the fog lamps when I realized what was happening; no change was observed.

    Could you please show me an image of the G104 ground and its location? I have found that the ETM is not always easy to "translate" into a location.
    1984 320i Baur TC2 5-Speed Opalgrün (Jeff's)
    1987 325e Sedan A/T Zinnoberrot (Dawn's)
    1984 633 CSi 5-speed Bronzit (Ours . . . if she says so)


  12. #12
    richardodn's Avatar
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    In the ETM, go to section 9000. The GROUNDS group is last. G104 is listed as "On inner fender, behind LH headlights" and the figure is 7000-1 fig 1.

    However if turning off the fogs had no effect, it's likely not that.
    "Howdy, Folks!"

    1986 Delphin 528e - Roof rack equipped lumber hauler.
    1989 Zinnoberrot 325iX Sedan - I miss this car. (Deceased)
    1998 Avus Blau 328iC - Someone else's project now
    2008 Platinum-Beige X3 3.0si - Current project
    2012 Alpine White X3 xDrive35i - My new snowmobile.
    2020 Estoril Blue 440i xDrive cabrio - This car is a blast to drive.

  13. #13
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    Thanks, Richard; I have ordered a new headlamp switch and I am in the process of trying to order a dimmer switch "just in case"; unfortunately, no NOS dimmer switches can be found so I will have to settle for "used".

    Can you tell me what I need to press/twist/do to get the old switch lose from the panel without destroying anything?

    Jeff
    1984 320i Baur TC2 5-Speed Opalgrün (Jeff's)
    1987 325e Sedan A/T Zinnoberrot (Dawn's)
    1984 633 CSi 5-speed Bronzit (Ours . . . if she says so)


  14. #14
    richardodn's Avatar
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    I can't remember. Wait until you get the new one. It might give you a clue.
    "Howdy, Folks!"

    1986 Delphin 528e - Roof rack equipped lumber hauler.
    1989 Zinnoberrot 325iX Sedan - I miss this car. (Deceased)
    1998 Avus Blau 328iC - Someone else's project now
    2008 Platinum-Beige X3 3.0si - Current project
    2012 Alpine White X3 xDrive35i - My new snowmobile.
    2020 Estoril Blue 440i xDrive cabrio - This car is a blast to drive.

  15. #15
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    The good news: I figured how to get the headlamp / fog lamp switch panel loose.

    The bad news: I disassembled the light switch and everything looked good inside. I cleaned the contacts and circuit board (which weren't very dirty) with some Berryman's carb cleaner and a paper towel. I lubed the rollers, reassembled and reinstalled it --- no change.

    Question: how in the world do I get the "second" panel retainer nut (up high and to the left of the switch panel) back on there?!? Is there a special trick?

    A couple of interesting observations:
    1) The low-beams will come on only when the high-beams are flashed; and
    2) so will the fog lamps (if the fog lamp button is "ON"; they will also come on with the high-beams ONLY.

    I'm leaning more toward "dimmer switch. Thoughts . .?
    1984 320i Baur TC2 5-Speed Opalgrün (Jeff's)
    1987 325e Sedan A/T Zinnoberrot (Dawn's)
    1984 633 CSi 5-speed Bronzit (Ours . . . if she says so)


  16. #16
    richardodn's Avatar
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    First remember that the outboard lamps are dual beams; not simply low beams. Just because they come on with the high beams tells you nothing about the low beam circuit. Stop swapping parts and start doing diagnostics with a multimeter.
    "Howdy, Folks!"

    1986 Delphin 528e - Roof rack equipped lumber hauler.
    1989 Zinnoberrot 325iX Sedan - I miss this car. (Deceased)
    1998 Avus Blau 328iC - Someone else's project now
    2008 Platinum-Beige X3 3.0si - Current project
    2012 Alpine White X3 xDrive35i - My new snowmobile.
    2020 Estoril Blue 440i xDrive cabrio - This car is a blast to drive.

  17. #17
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    I'm with Richard, do you have a good multimeter? Pick a side, left or right, see what power and grounds do you have. Again, along with Richard, I think the high beams being on are getting you a ground that you don't have with just the low beams. The low beams get power two ways but one ground.

    Do you have a wiring diagram?
    2004 525i Sport, Manual - 1985 325E Coupe Manual

  18. #18
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    Thanks, Tom; I'll check it out. Yes, I have the ETM and also a laminated multi-color diagram; I'll get into it today.

    So, Richard, are you still leaning toward that ground behind the left-hand headlamps? If so, please tell me it is not located beneath my ABS system . . .

    Jeff


    1984 320i Baur TC2 5-Speed Opalgrün (Jeff's)
    1987 325e Sedan A/T Zinnoberrot (Dawn's)
    1984 633 CSi 5-speed Bronzit (Ours . . . if she says so)


  19. #19
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    UPDATE:

    Richard, I followed your advice and located what I believe to be the headlamp ground wire cluster: four large-gauge brown wires secured to the forward left inner fender by a 6mm bolt. I could find no other grounds in that vicinity.

    All were very rusty, so I cleaned the terminals and mounting surface thoroughly with a steel brush (the bolt I bead-blasted), chased the female threads in the fender with a tap and reinstalled the wires with liberal amounts of dielectric grease. No change. :-(

    Question: would it be likely that the low-beam filaments would blow simultaneously in both of those outer bulbs? I run Sylvania Xtravision sealed-beam bulbs, installed about 1.5 years ago.

    Any other suggestions . . .?

    Jeff
    1984 320i Baur TC2 5-Speed Opalgrün (Jeff's)
    1987 325e Sedan A/T Zinnoberrot (Dawn's)
    1984 633 CSi 5-speed Bronzit (Ours . . . if she says so)


  20. #20
    richardodn's Avatar
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    The lamps would typically burn out around the same time as they would typically have the same number of hours. However simultaneously is very unlikely.
    "Howdy, Folks!"

    1986 Delphin 528e - Roof rack equipped lumber hauler.
    1989 Zinnoberrot 325iX Sedan - I miss this car. (Deceased)
    1998 Avus Blau 328iC - Someone else's project now
    2008 Platinum-Beige X3 3.0si - Current project
    2012 Alpine White X3 xDrive35i - My new snowmobile.
    2020 Estoril Blue 440i xDrive cabrio - This car is a blast to drive.

  21. #21
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    Thanks, Richard.

    Since the last time that I had a similar (though not identical) problem it turned out to be the dimmer switch (which I replaced with a functioning switch that was four years older than the car), I bit the bullet and bought an NOS switch; it should be here tomorrow.

    Jeff
    1984 320i Baur TC2 5-Speed Opalgrün (Jeff's)
    1987 325e Sedan A/T Zinnoberrot (Dawn's)
    1984 633 CSi 5-speed Bronzit (Ours . . . if she says so)


  22. #22
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    Well, long story short: it wasn't the headlamp switch or the dimmer switch, it wasn't the headlamp bulbs and it wasn't a fuse. I don't think it is the relay, but I have an OEM Bosch "purple" relay on order right now "just in case".

    Any other suggestions? I can't be the first E30 owner on the planet to have this problem . . . can I?


    Jeff
    Last edited by BMWtyro; 01-31-2022 at 07:36 PM.
    1984 320i Baur TC2 5-Speed Opalgrün (Jeff's)
    1987 325e Sedan A/T Zinnoberrot (Dawn's)
    1984 633 CSi 5-speed Bronzit (Ours . . . if she says so)


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