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Start control switch model 412

Discussion in '365 GT4 2+2/400/412' started by PetMar, Aug 30, 2019.

  1. PetMar

    PetMar Rookie

    Aug 31, 2018
    38
    Izegem, Belgium, Europe
    Full Name:
    Marrannes Peter
    Good day Everyone.

    I am starting to experience starting problems with my 412 with automatic gearbox. I suspect my start control switch to abandon me. Until now I always got the car started by switching from P to N, or vice versa a few times but my fear is it will be over and done suddenly. Does anyone have experiences with this problem? Upon inspection, Slide 023 Outside Gearbox Controls - 412 A part 118217, it appears that part can still be ordered. Or can the part be repaired?

    Looking for parts, I often see: Only for CH Model.
    What does this matter, what is the difference?

    My VIN: ZFFYD24B000059361

    Mid January I have an appointment to have all rubbers, joints and bushes of the suspension and steering replaced. If I now knew that I can continue, even with the doubtful feeling, I would wait for repairs until then. The weather is now so good that I prefer not to return the car now for a repair that will take a while. Ordering a piece, bringing the car in, repairing it, picking it up again, you know it.

    What do you recommend?

    Have a nice weekend.

    Peter
     
  2. SouthJersey400i

    SouthJersey400i Formula 3

    Mar 14, 2007
    1,200
    Romulus, NY (Finger Lakes)
    Full Name:
    Ken Battle
    Peter
    Is the problem that you are unable to turn key in switch and get it to work? Do you know if 412 has same German steering wheel lock / ignition switch as the 400i? There is a good thread about what to replace if your key is loose and it does not work. There is a relatively low cost BMW part on back of key module that can be replaced in 15 minutes. I'm just not sure this is your issue.
    Ken
     
  3. PetMar

    PetMar Rookie

    Aug 31, 2018
    38
    Izegem, Belgium, Europe
    Full Name:
    Marrannes Peter
    Ken,

    Thanks for your reply.

    Problem is, with the gearbox in P, when I turn the key, I see the red alternator light and the red ABS light and I hear the pumps working. But the starter does nothing. Then I switch to N and with any luck the engine fires up. Sometimes I have to repeat that move several times before it fires up. So, I don't think it is all about the key. What I didn't try so far is, when I put the gearbox in R, and turn the key, to have a look at the reverse lights. But I am almost sure the start control switch is the culprit.

    Peter
     
  4. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    18,727
    Texas
    Full Name:
    Steve Magnusson
    "Only for CH Model" = Only used on Swiss version (not used, and often not even present, on standard/euro version).
     
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  5. SouthJersey400i

    SouthJersey400i Formula 3

    Mar 14, 2007
    1,200
    Romulus, NY (Finger Lakes)
    Full Name:
    Ken Battle
    It sounds like the fault may be a GM switch in or on the transmission.
    Ken
     
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  6. raemin

    raemin Formula Junior

    Jan 16, 2007
    318
    Lyon (FR)
    Full Name:
    R. Emin
    #6 raemin, Aug 31, 2019
    Last edited: Aug 31, 2019
    I am not sure there is such switch on the th400, the 2/4 pin prong on the left side is for the kickdown and pitch control. It seems the control is performed by the brown rotary part on the right of the shifter.

    Image Unavailable, Please Login

    The harness (red/white and white/black) is quite easy to access as it is just under the autoradio. Should be easy to override if need be.

    Image Unavailable, Please Login
     
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  7. raemin

    raemin Formula Junior

    Jan 16, 2007
    318
    Lyon (FR)
    Full Name:
    R. Emin
    Note that I cannot see in the diagram how this is suppised to work... either my magnifying glasses are not big enough or they just forgot to document it as it just seems that the positive is tapped on one of the first two fuses and goes directly to the neiman and starter?
     
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  8. raemin

    raemin Formula Junior

    Jan 16, 2007
    318
    Lyon (FR)
    Full Name:
    R. Emin
    Commenting my own reply... It is indeed specified in the additional diagram, page 123 of 1979 Owner Manual (400i) ref 176-79 . The round commutator (ref 150) is actuating relay 148 which enables/disables the starter. Not sure as to what is relay 148 on the newer relay box, but seems to be relay Z (it's called "relay for starter").

    Judging by the diagram it seems that the round dial shorts the two red wires you see in my picture when P or N is engaged. When these two are shorted the relay is "On", and hence can allows to trigger the starter.

    Could be a faulty relay as the amp-draw of the starter solenoid is quite significant (on the 365 the ammeter shows approx 20amps), other than that, the round commutator would need to be reviewed. Just in case, move the red wires, in an accessible location so as to be in a position to short them and avoid to be stuck in the middle of nowhere...

    Now time to find what this purple/blue undocumented wire is supposed to do on my own car! (It's just next to the shifter, hence my comprehensive finding for your own problem)
     
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