News

'89 TR Keeps Popping Fuse

Discussion in 'Technical Q&A' started by Jerrari, May 27, 2004.

  1. Jerrari

    Jerrari F1 Veteran

    Jul 24, 2001
    5,458
    Michigan
    Full Name:
    Jerry Wiersma
    Any suggestions on where to look for most likely source of the short? It's the 7.5 Amper that controls the instrument lights and side marker lights. Sometimes the fuse will last a day, sometimes 5 minutes. Thanks, Jerry.
     
  2. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    19,268
    Texas
    Full Name:
    Steve Magnusson
    Jerry -- I'll have a peek at the TR wiring diagram tonight, but based on the items that circuit runs it all seems straight-forward. A couple of questions you could work on 'til then:

    1. When it is working, are all the side marker lamps, number plate lamps, rear tailight lamps illuminating normally -- parking lights, turn signals, hazard, brake? (I'm wondering if some bad ground somewhere is causing extra current to flow in that parking light circuit -- e.g., like it's a combination thing "parking lights on + turn signals = bad" or "parking lights + reverse lights = bad" -- but can't really even say this might be a real possibility yet with looking at the WD.)

    2. Have you tried measuring the current flowing thru that fuse position when things are working normally?

    3. I can't recall if the number plate wires are at risk for touching the exhaust system, but you might check that too.
     
  3. Dr_ferrari

    Dr_ferrari Formula 3
    Professional Ferrari Technician Consultant

    Nov 2, 2003
    1,064
    Pocono Sportscar
    Full Name:
    Jim McGee
    unplug the electric connectors for the rear bonnet struts. the struts are intermittantly shorted to ground causing your problem. You have to replace the struts to fix the problem.

    best regards, Jim
     
  4. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    19,268
    Texas
    Full Name:
    Steve Magnusson
    Jerry -- I checked the WD, and as Jim already indicated, the parking light "+" network connects via the RH engine bonnet strut to also run the "Engine compartment lights" (which is the only "not straightforward" thing about the whole parking light network). You'll only need to unplug the connector with two yellow wires at the base of the RH strut (the red wire connector on the LH strut runs the CHMSL). All of your exterior parking lights will still function OK with the yellow connector unplugged so you can try it that way as a real-world test no problem.
     
  5. Dr_ferrari

    Dr_ferrari Formula 3
    Professional Ferrari Technician Consultant

    Nov 2, 2003
    1,064
    Pocono Sportscar
    Full Name:
    Jim McGee
    exactly, just unplug the right strut and check the operation. if the fuse no longer blows out...you found your problem. also, look close at the strut for contact with the chassis when closed. the power for the lights flows through the strut and if the strut is rubbing against the bonnet or chassis, it will short out.

    best regards, Jim
     
  6. pino

    pino Karting

    Nov 1, 2003
    208
    South Central PA

    May I ask, WHY?

    Sounds more crazy than the usual F-car engineering, no?
     
  7. Jerrari

    Jerrari F1 Veteran

    Jul 24, 2001
    5,458
    Michigan
    Full Name:
    Jerry Wiersma
    Thanks a lot guys, I'll unplug the wire and see what happens. Jerry.
     
  8. Jerrari

    Jerrari F1 Veteran

    Jul 24, 2001
    5,458
    Michigan
    Full Name:
    Jerry Wiersma
    OK, I found the wire and unplugged it. I put in a new fuse and it so far passed the 5 minute test. I'll take it for a drive tomorrow and see what happens. Thanks again!!
     
  9. Jerrari

    Jerrari F1 Veteran

    Jul 24, 2001
    5,458
    Michigan
    Full Name:
    Jerry Wiersma
    Steve and Jim,
    The right strut was rubbing against the bonnet ever so slightly. The mounting bracket at the bottom of the strut was bent in a little bit. I bent it back outward....problem solved! Thanks a million!!
     

Share This Page