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Please help 1989 Testarossa blowing fuse #13 for parking lights

Discussion in 'Boxers/TR/M' started by Marc Jackson, Feb 12, 2020.

  1. Marc Jackson

    Marc Jackson Rookie

    Jan 10, 2020
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    Cape Cod, Ma
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    Marc Jackson
    Hello everyone my 1989 Testarossa has been blowing the #13 fuse for the parking lights, dash lights, plate lights, engine compartment lights and front bonnet lights. I inspected the fuse box and found some burnt terminals and previous relay repairs that weren’t pretty so I sent the fuse panel to a company that rebuilds them with modern circuit boards. Hoping that this would possibly be my fix I installed the new fuse panel today to find that it is still blowing the #13 fuse. I have a tough to follow wiring diagram that I was able to print off the internet so I’m not just poking around in the dark but I’m starting to get frustrated. Any help would be greatly appreciated thanks in advance
     
  2. V4NG0

    V4NG0 Karting
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  3. turbo-joe

    turbo-joe F1 Veteran
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    have a look at the rear hood shock right side. this one is for the engine compartement light. I once had the same problem. just disconnect the wire coming from the car to the shock and see what will happen
     
  4. Marc Jackson

    Marc Jackson Rookie

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    Thanks for the reply joe I have disconnected all of that in the rear the connectors at the struts all the parking light connectors still blows fuse
     
  5. turbo-joe

    turbo-joe F1 Veteran
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    oh ! ! !
    then happy hinting ;)
     
  6. Steve Magnusson

    Steve Magnusson F1 World Champ
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    If you've got the G (yellow) wire unplugged from the bottom of the RH engine bonnet gas spring, and the fuse #13 still blows, the next easy thing to do is check to see if the license plate light wiring has melted onto the exhaust system somewhere.
     
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  7. Marc Jackson

    Marc Jackson Rookie

    Jan 10, 2020
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    Marc Jackson
    I have the license plate harness all unplugged still blows fuse. If someone has any info of what I should see for power and grounds at the exterior light relay terminals with the light switch turned to parking lights and the switch turned off would be helpful. These diagrams are very tough to read and decipher.
     
  8. Steve Magnusson

    Steve Magnusson F1 World Champ
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    Phfffft! -- be thankful that you don't have a 512TR -- those schematics are truly user-hateful! ;)

    First, a couple of questions;

    1. Please indicate what version TR. US? euro? GB? Something else?

    2. Does fuse #13 always blow the instant you rotate the stalk knob to "on", or does it have some other behavior (please describe)?
     
  9. Marc Jackson

    Marc Jackson Rookie

    Jan 10, 2020
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    Really I can’t imagine them getting any worse lol
    It is a US version.
    As soon as the stalk is turned on it blows the fuse. To aid in diagnosing my problem and to stop popping fuses every time I want to check to see if I’ve found a problem I bought I circuit breaker that takes place off the fuse and instead just trips the breaker switch rather than wasting another fuse. I tried to put in a slightly higher breaker just to see what happened and noticed the lights lit dimly before tripping the breaker. I didn’t want to continue doing this for fear of causing more damage. I have the entire center console removed and the harness. The instrument cluster has been removed. I also installed an upgraded fuse panel from Gtcp.com (really a quality product I must say) as there were numerous burnt terminals and a fuel pump relay bypass/repair that I wasn’t comfortable with.
    Some measurements I’m getting at the terminals of the “K” relay with the switch in the off position: 12v at pin 30, 12v at pin 85, 12v at pin 86, and both pins 87 and 87b are grounded
    With switch turned to the on position pin 85 turns to a ground causing the relay to switch
     
  10. Steve Magnusson

    Steve Magnusson F1 World Champ
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    #10 Steve Magnusson, Feb 13, 2020
    Last edited: Feb 13, 2020
    I like that a lot as it should make figuring it out easier -- an intermittent Gremlin is far more difficult.

    Nothing wrong with those measurements, but 87 and 87b are really the loads, not grounds. They just measure as ground with the relay "K' removed because all the bulb filaments in parallel are a very low resistance. The way relay "K" works (when "on") is it connects the 12V on terminal 30 to both terminals 87 and 87b to run the loads. The trouble you are having is that one of those currents is presently too high.

    My suggestion would be to unplug the x, y, and c white connectors at the fuse-relay panel, and then turn the stalk knob "on" -- if the fuse #13 (or the circuit breaker you are using there) still blows = bad sign for the fuse-relay panel itself, or bad relay "K", or maybe you have some added modification somewhere. If it does still blow, as a test, you can always substitute one of the ...113 relays for relay "K". If it doesn't blow/trip, try plugging those connectors back in one at a time until it does blow/trip. If you can identify which of those white connectors has the problem circuit, that will narrow down where to go next. Once you know which white connector has the problem circuit, give a shout back, and we can go further downstream on the things that that connector serves.
     
  11. Marc Jackson

    Marc Jackson Rookie

    Jan 10, 2020
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    Ok Steve first off I would just like to say thank you for helping me with this... it seems that the issue is with connector X
     
  12. Steve Magnusson

    Steve Magnusson F1 World Champ
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    #12 Steve Magnusson, Feb 13, 2020
    Last edited: Feb 13, 2020
    Always glad to lend some small assistance to a fellow TRer.

    White connector x serves 3 bulb things -- the LH ashtray lamp, the RH ashtray lamp, and the dimmer rheostat so the same strategy would be to unplug the LH door connector C1 (it's near the brake booster under the carpet piece), the RH door connector C9 (it's on the other side of the cowl under the carpet piece), and the 9-pin connector for the instrument cluster than has the pin with two B (white) wires (with the x connector plugged back in) -- then replug each of those connectors to identify which one has the problem.
    Here's a shot of the C1 connector location (C9 is in a similar place on the other side):
    Image Unavailable, Please Login
     
  13. Marc Jackson

    Marc Jackson Rookie

    Jan 10, 2020
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    Steve you sir are a legend! I can’t thank you enough for the time you took to help me with this problem. I traced it to the drivers side ashtray light wires. Turns out at some point in it’s life the drivers window regulator motor and glass guides had been disassembled cleaned and lubed but when that person mounted the window motor they trapped the ashtray harness under it and tightened it down creating a dead short between the two wires. Again thank you so much for taking the time to help me with this. Now I get to tackle cam cover gaskets on my uncles Diablo. Image Unavailable, Please Login
     
  14. Steve Magnusson

    Steve Magnusson F1 World Champ
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    Glad that you got it sorted, and thanks for the feedback to close the issue. IIRC, yours is the first case of fuse #13 blowing that didn't involve the RH engine bonnet gas spring or the license plate wiring, but it makes perfect sense as you describe. I've actually got disabling the ashtray lights on my list of things to do (as I find them kind of annoying), but it has never made it to the top of the list ;).
     
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  15. turbo-joe

    turbo-joe F1 Veteran
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    yes steve, electrical gremlins always going their own way ;)
    for me also it is the first time I got knowledge about this ashtray light failure.
    what a great error search machine this forum is :)
    great marc that you found the mistake and published here
     
  16. Marc Jackson

    Marc Jackson Rookie

    Jan 10, 2020
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    Being new to the forum I was glad to see people truly offering help I’ve tried asking questions in forums before and you just get a bunch of people spewing nonsense. Thank you again for the help look forward to talking again soon
     
  17. ago car nut

    ago car nut F1 Rookie
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    Steve is really good at electrical problems!!
     
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  18. Prova85

    Prova85 Formula 3

    Nov 13, 2003
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    Marc, welcome to fchat. I see you're down the cape. Hope to you meet you and see the car this year at some local events.
    Not many Tr's around these parts. Good to see there's one on the cape!
    There's an upcoming event you may be interested in for Mission 22 (charity that fights veteran suicides) in March at the Factory 5 factory in Wareham. PM me if you're interested in the details and what it's all about.
     

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