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348 Another headlight issue...

Discussion in '348/355' started by FSM348, Sep 10, 2019 at 8:17 AM.

  1. FSM348

    FSM348 Karting
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    Feb 13, 2017
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    My 91 348 is having some strange headlight issues similar to what the search results have shown. However, it is definitely not a moisture issue due to not being around water for 3 years and is kept in a climate controlled garage.

    I've tried swapping relays that results in different issues rather than fixing the problem

    With all relays in correctly the headlights will pop up and down continuously even with key out of ignition.
    Removing the "LH headlight relay" and/ or "RH headlight relay" (0332204101) does nothing.
    Removing "control headlight relay" solves this but of course makes them inoperable at that point.
    If I swap the AC relay (0332014113) with the "control headlight relay" the motors will stop popping up and down with key out of ignition, however, once key is turned to "ON" the headlights will begin popping up and down again continuously until key is turned "OFF"

    I've also tried swapping several of the (0332204101) relays with others of the same part number with no change. Do both hi beam and low beam light bulbs need to be in the headlights and operation for the motors to work correctly? I can't imagine this being the case and I assume it is something else entirely.

    I don't think it is the headlight stalk as all positions seem to work correctly according to fog light, turn signal, windshield operation as well as high beam dash light in correct order.

    Thanks for any help.
     
  2. Qavion

    Qavion Formula 3

    Feb 20, 2015
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    Strange. I assume you mean that the headlights pop up and down with the ignition off and the headlight switch on, or does it happen with the headlight switch off and you have to use the battery cutoff switch to stop this happening?

    I've been looking at the circuit for the last hour and not making much headway. I'm wondering if a shorted diode in one of the headlamp motors could cause this problem. Unless someone comes up with an alternative, easier faultfinding path, could you disconnect the two plugs on one headlight motor to see if it restores operation to the other headlight lifting system? If not, try disconnecting the plugs on the other headlight motor (reconnect the other one).
     
  3. Qavion

    Qavion Formula 3

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    Dan, when the headlights pop up, are they illuminated?

    Why do you ask? Have you removed the bulbs?
     
  4. Qavion

    Qavion Formula 3

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    Before you start pulling plugs off the motors, in theory, you could check for a shorted diode by pulling the control relay ("a") in the forward luggage compartment and, with the battery off, use a multimeter to check for continuity between contacts 87 and 87a of the relay socket (reverse the ohmmeter leads if you get an open circuit). If you get an open circuit in both directions, the diodes should be ok.

    If you do get continuity (or a small resistance) with this check, it won't tell you which of the headlight pod diodes are faulty, so you'll have to disconnect both "stepped" connectors on one side of the car.
     
  5. Qavion

    Qavion Formula 3

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    #5 Qavion, Sep 11, 2019 at 12:45 AM
    Last edited: Sep 11, 2019 at 12:54 AM
    Further thoughts...

    The headlight lift relay (a) or the "control headlight relay" as you call it, puts out (battery) power to the headlight pod gearboxes irrespective of whether the relay is energised or not. The AC relay you substituted would only put out power with the relay energised. This suggests that the stalk switch input seems to be ok (as you surmised) as the substitute relay's state was altered by the stalk switch.

    As you didn't replace the headlight lift relay (a) with the same type, why not try swapping the relay with the same type if there are any (Does the daytime flasher relay "g" have the same part number?). We don't yet know if this relay is part of the problem. There may be multiple factors.

    Here's the diagram:

    F348 Headlight wiring diagram (sans column switch shown)

    You didn't state the part number of the "control headlight relay". Does it have the same part number as the L&R lifting relays?

    (EDIT) I'm starting to rethink my earlier theory about shorted diodes, but taking one headlight motor/gearbox out of the equation by disconnecting the two plugs on one side still sounds like a good idea. How easy are these plugs to get on the F348 (hopefully easier than the F355).
     
  6. m.stojanovic

    m.stojanovic Formula 3
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    I do not remember how the actual two 2-pin (stepped) connectors for each lift motor look but, according to the diagram, they seem to be the same (are they different colour?). If the connectors are swapped over between the two of them at each motor (connected wrongly) this will bring permanent 12V to each motor so it will continuously run (with the ignition and the light switch off). Worth double checking whether the 2-pin connectors are connected correctly.
     
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  7. Qavion

    Qavion Formula 3

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    I recall the plugs are black and white on the F355. Not sure about the F348.

    If the plugs are the same colour, comparing wire colours on either sides of the plugs might offer a clue. On the F355, the green-black wire has a green-black wire counterpart. The rest have mismatching colours however.
     
  8. FSM348

    FSM348 Karting
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    Thanks for the help so far!

    The “headlight control” relay is the same as the LH and RH headlight relays. I actually tried a brand new relay from oriellys (0332209151) which is a crossover part according to Bosch website with same result.

    It is possible to have the motor power plugs reversed as they are both identical so I will try swapping them tonight after work and yes they are a PITA to get to.

    I will also try checking power at the relay pins with “headlight control” relay removed.

    I will post results this evening
     
  9. m.stojanovic

    m.stojanovic Formula 3
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    Do not swap them if you find that they are connected with the colours matching. On the other hand, they might be covered in dust/dirt so make sure you can actually see their colours. Here's a pic of a 348 motor showing that one connector is black and the other white (well, dirty white).

    Image Unavailable, Please Login
     
  10. Qavion

    Qavion Formula 3

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    Hard to tell for sure, but the colours on the motor look similar to the 355's, so I'll mark the 348 diagram accordingly.

    Headlight Wiring Diagram

    At the control relay you should have:

    pin 30 : hot battery power
    pin 85 : ignition power (if the ignition is on)
    pin 86 : earth if the light switch is on
    pin 87 : Probably no volts, but I'm not sure about the resistance anymore... It looks like it depends on where the gearbox is in its cycle. It might show headlight relay coil resistance. I'm wondering if the ohmmeter voltage will trigger the headlight relays.
    pin 87a: ditto
     
  11. FSM348

    FSM348 Karting
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    Fixed it. Both motor power connectors were reversed. Changing just one did not solve the issue so both had to be swapped. Thanks guys!!!
     
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  12. Ferrarium

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    For clarity they did not work one day then stop the next. I assume you got the car and they never worked or you did work on it and reversed the connections?
     
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  13. FSM348

    FSM348 Karting
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    I had both headlights out of the car and when installing them back into the car I did not notice the different color connectors because at some point the connectors had electrical tape on them which made them both appear black. With a little rubbing alcohol I could then see the white body connectors under the tape residue. Thanks everyone! Hopefully this helps out others as well. Top Tip: Make sure the three headlight relays part numbers end in 101 if they are original metal. I believe the numbers are 0332204101. New ones can be 0332209150 or 0332209151. They should have the circuit diagram on the side of them (some do) so make sure it matches and your good as well as the 5 pins in correct orientation. I got a new one at Orielly's for $13 although I didn't end up needing it.
     
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