News

512 TR Engine compartment/trunk open lights

Discussion in 'Boxers/TR/M' started by Clyde Romero, Oct 11, 2019.

  1. Clyde Romero

    Clyde Romero Formula Junior

    Sep 6, 2019
    250
    Atlanta Georgia
    Full Name:
    Clarence Romero
    My 1993 512 TR engine compartment and hood open lights will not show open when they in fact are unlatched
    I doubt seriously if both bulbs are burned out
    Can’t seem to find a fuse associated with this system
    Any ideas on how to trouble shoot this ?
     
  2. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    18,730
    Texas
    Full Name:
    Steve Magnusson
    Some questions:
    1. What version 512TR? US or euro?
    2. Does the red handbrake "on" warning light on the LH side of the dash work (when the handbrake is "on" and key "on" ;))?
    3. In the middle of the row of these lights is the red "brake warning light" -- does this illuminate during starter motor cranking?
     
  3. Clyde Romero

    Clyde Romero Formula Junior

    Sep 6, 2019
    250
    Atlanta Georgia
    Full Name:
    Clarence Romero
    Answers
    1. US car
    2. Handbrake light on with key on and handbrake on
    3. During the starter cranking the Red brake light DOES NOT ILLUMINATE
     
  4. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    18,730
    Texas
    Full Name:
    Steve Magnusson
    That's a bit of a curve ball. The two bonnet open lights, the handbrake light, and the brake warning light all use the same +12V source so seems odd that the handbrake light works but the brake warning light doesn't work. However, I may be misreading the OM description -- does the brake warning light come "on" when you first turn the key "on", and then go out after a second or two?

    However, since your handbrake warning light does work, that is still a very strong sign that you do have +12V available to run the bonnet open lights, and you either have:

    burned out, or missing, bulbs,
    bad switches,
    or wiring problems on the ground/switch side of the bulbs (the front bonnet has two independent switches and the rear bonnet one switch)
    (or some combination of all three faults)

    My advice would be to remove the bonnet switches (or at least remove them enough to get to their wires) and directly connect the two wires together (simulating an open bonnet and a closed switch):

    A. If the corresponding bonnet open light does come "on" with the switch wires electrically connected and the key "on" = buy a new switch.

    B. If the corresponding bonnet open light doesn't come "on" with the switch wires electrically connected and the key "on" = pretty strong sign the bulbs are burned out or missing. A further test would be to measure the voltage between each of the wires at each switch (with key "on") and another good ground -- one of them should measure +12V if the bulbs are present and good:

    If neither wire at each switch measures +12V relative to a known good ground with key "on" = pretty strong justification to check the bulbs.

    If one of the wires at each switch does measure +12V relative to a good ground, but the bulb doesn't come "on" when the switch wires are connected together = worst situation as that would indicate a wiring problem somewhere else on the ground side.

    If you can try some of those things, and report the results back, would be glad to help reread the tea leaves...
     
  5. Clyde Romero

    Clyde Romero Formula Junior

    Sep 6, 2019
    250
    Atlanta Georgia
    Full Name:
    Clarence Romero
    The brake warning light does not come on then go out when starting the car it stays completely off
    Will run through you checks this weekend and get back with you
    Thanks for your diagnostic on the system
    I doubt seriously if both bulbs are burned out but it could be
     
  6. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    18,730
    Texas
    Full Name:
    Steve Magnusson
    If you're saying that your brake warning light has never ever illuminated = that's a problem, too (but probably not related to your bonnet open lights issue if the handbrake warning light is working).

    Agree it seem unlikely that both bulbs have burned out, but it's sort of equally unlikely that three completely independent switch + wiring systems would all have a problem, too -- will be interested to learn what you find.
     
  7. Clyde Romero

    Clyde Romero Formula Junior

    Sep 6, 2019
    250
    Atlanta Georgia
    Full Name:
    Clarence Romero
    Steve just to be clear the lights on both bonnets are out when they are open
     
  8. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    18,730
    Texas
    Full Name:
    Steve Magnusson
    Wait -- are you saying;

    1. The lights mounted on each bonnet don't light up when they are opened (I believe these only do when the exterior parking lights are "on"), or

    2. The red warning lights in the dash to indicate that the bonnets are unlatched don't light up when the bonnets are unlatched and the key is "on"?

    My response assumed #2.
     
  9. Clyde Romero

    Clyde Romero Formula Junior

    Sep 6, 2019
    250
    Atlanta Georgia
    Full Name:
    Clarence Romero
    #2 is correct
    Ignition on
    Bonnets open
    No warning lights on dash

    don’t know if I can get to it today
    My foot is acting up Gout
    Getting old 70

    so what your telling me is the brake warning light is tied into the bonnet open system ?
    The parking brake warning light works fine no issues there


    when I have looked at the locking mechanism trying to figure this out myself a while back I see a brown wire to the lock on the front one and the back one if I remember correctly has the same lay out
    No broken wire that I could see

    I just find it strange that both lights are out
    I don’t mind removing the dash
    Done it before to replace the Tach and the leather instrument pod
    Printed out your instructions
    Will try to get to in this week
     
  10. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    18,730
    Texas
    Full Name:
    Steve Magnusson
    Yes, both system share the same +12V power coming from the same wire in the dash.

    The warning switches on the front latches are item 23 here:
    https://www.ricambiamerica.com/car-diagrams/ferrari/v12/testarossa-group/512tr/front-hood.html
    The 512TR schematic shows they have a brown wire and a black wire. Not specifically familiar with them, but possible they could be mis-adjusted, or broken, in addition to being electrically bad.

    The rear latch uses the same warning switch -- item 36 here:
    https://www.ricambiamerica.com/car-diagrams/ferrari/v12/testarossa-group/512tr/rear-hood.html
    The 512TR schematic shows this one having a brown-green wire and a black wire.

    You should ;) If the switches aren't the trouble, the voltage measurements at the switch wires should give you the evidence for whether you need to get to the bulbs or not.

    Good Hunting!
     
  11. 302Tim

    302Tim Formula 3
    Silver Subscribed

    Jul 2, 2011
    1,155
    Northern California
    Full Name:
    Tim
    Just want to make sure you didn't miss Steve's note in post #8...these lights will only illuminate when the bonnet/hood is open/opened and the external lights are switched on (position I or II)...at least on the Testarossa--I believe same for 512TR.
     
    peteficarra likes this.
  12. Clyde Romero

    Clyde Romero Formula Junior

    Sep 6, 2019
    250
    Atlanta Georgia
    Full Name:
    Clarence Romero
    That’s incorrect for the 512 TR if your ignition is on and the bonnets are open you should have warning lights on
    You don’t need headlights on for the warning lights to be on
     
  13. Clyde Romero

    Clyde Romero Formula Junior

    Sep 6, 2019
    250
    Atlanta Georgia
    Full Name:
    Clarence Romero
    Just to be clear these two switches when the bonnets are open complete the circuit and illuminate the lights correct?
    So I should have 12 volts at both ends with the car ignition on
    And when I close the circuit by touching to two wires together I should get a light on showing the bonnets open
    That’s the way I see it

    let me know if I am incorrect here
     
  14. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    18,730
    Texas
    Full Name:
    Steve Magnusson
    Yes (there are actually three switches -- the front bonnet has two switches acting in parallel, and the rear bonnet one switch)

    Yes, the brown wires at the front switches and the brown-green wire at the rear switch should be +12V relative to ground with the key "on" if the warning lights are not "on" (if the bulbs are OK).

    Yes, with the key "on" and if the problem is a bad, broken, or mis-adjusted switch.
     
  15. Clyde Romero

    Clyde Romero Formula Junior

    Sep 6, 2019
    250
    Atlanta Georgia
    Full Name:
    Clarence Romero
    ok great
    Will tackle this hopefully this week
    Need to stay off my foot for a while but now at least I understand the circuit
    One more question
    If have 12 volts at the green/brown wires at both ends
    It’s must be the bulbs, correct?
     
  16. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    18,730
    Texas
    Full Name:
    Steve Magnusson
    No, if you DON'T have +12V on the brown wires (front) and brown-green wire (rear) with key "on" and the warning lights not "on" = justifies getting into the dash to check the bulbs and their sockets.

    If you do have +12V on those wires with key "on" and the warning lights not "on" = almost certainly confirms that the bulbs are OK.

    If you do have +12V on those wires with key "on" and the warning lights not "on", but the bulbs don't illuminate when you connect the brown wire to the black wire (front) or the brown-green wire to the black wire (rear) = wiring problem (or bad corrosion in the sockets) = we don't want to go here ;).
     
  17. Clyde Romero

    Clyde Romero Formula Junior

    Sep 6, 2019
    250
    Atlanta Georgia
    Full Name:
    Clarence Romero
    Ok
    I think I’ve got it now
    Will let you know what I’ve found out
    Once again thanks for all your assistance in this problem
     
  18. JIMBO

    JIMBO Formula 3
    Silver Subscribed

    Oct 31, 2003
    1,035
    Bradenton, Florida
    Full Name:
    Jim DeRespino
    Who's on first...
     
  19. Clyde Romero

    Clyde Romero Formula Junior

    Sep 6, 2019
    250
    Atlanta Georgia
    Full Name:
    Clarence Romero

    ok here is what I got
    sorry I have taken so long to get back with you
    I have 12volts at the rear switch with the ignition on
    I jumped the wires NO LIGHT ON in the DASH
    I have not checked the front switch yet
    but based on what you sent me earlier it must be the bulbs ? YES ?
    my cell is 678 6419932 if you want to call me
    thanks for taking time out to assist me with this problem
    I just find it weird that both bulbs would be burned out front and rear
    but stranger things have happened
    awaiting your reply
     
  20. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    18,730
    Texas
    Full Name:
    Steve Magnusson
    Having the +12V present at the switch with key "on" is a good sign for the bulb filament.

    Use a jumper wire (or if you can do it directly) connect the wire at the switch where you measure +12V to a good ground (like the bare engine block or bare cylinder head). Two possibilities:

    1. If the bulb illuminates = you have a bad connection in the wiring going from the other side of the switch to ground, or

    2. If the bulb does not illuminate = most likely you have a bad connection at the bulb/bulb socket or upstream of the bulb socket. The bad connection is not fully open (infinite ohms), but, if it has say a resistance of 5000 Ohms, you would get the result you are getting (where it seems the +12V is there when the current is 0A, but the bulb doesn't work when it's connected to ground

    If #2, give a shout, and I'll see if there are any other obvious suspects to check.
     

Share This Page