Running lights...popping fuse when I turn on the lights | FerrariChat

Running lights...popping fuse when I turn on the lights

Discussion in 'Technical Q&A' started by LSU348, Jan 9, 2004.

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  1. LSU348

    LSU348 Formula 3

    Dec 19, 2003
    1,047
    Sugar Land
    Full Name:
    Mike
    #1 LSU348, Jan 9, 2004
    Hey guys,

    About every 5th or 6th times I cut on the lights the RF and RR and rear right main running light fuse pops. The owner and a mechanic (who I did not talk to) say it has to do with the starting current the light motors pull when they open. That is a possibility but not one I can diagnose without a detailed wiring diagram.

    Anybody have this problem before? I think I will measure the resistance across the system and calculate the current from 12 volts. If it is real high I will solder a resistor/heat sink in series in the trunk area to cut down on the current.

    Just got her today...the owner refunded me some $$ when the fuse popped. I can fix it myself for the cost of what he refunded me. The electrical system and I are about to get very intimate. After that all the other stuff I want to "fix" is cosmetic or routine.
     
  2. jselevan

    jselevan Formula 3

    Nov 2, 2003
    1,873
    #2 jselevan, Jan 9, 2004
    LSU - don't get esoteric. I had the same problem in the Boxer. Proved to be a burnt and exposed wire swinging and hitting the muffler at the right-rear lamp assembly. Check the wires going to your rear lamps and make sure the heat of the muffler has not burnt through the insulation.

    Just a thought.

    Jim S.
     
  3. LSU348

    LSU348 Formula 3

    Dec 19, 2003
    1,047
    Sugar Land
    Full Name:
    Mike
    #3 LSU348, Jan 9, 2004
    Yes, that is mission one. Chase the wire from point a to point b. It is actually amazingly accessable on the 308. Too dark to do that tonight - will have a look tomorrow morning. That is why I am doing a resistance check on the whole system...if I get a short from the power wire to ground I know I have something exactly like you are mentioning.

    For the record...yes...I will pull the fuse before checking line resistance :)

    Thanks for the reality check.


     
  4. jselevan

    jselevan Formula 3

    Nov 2, 2003
    1,873
    #4 jselevan, Jan 9, 2004
    LSU - unfortunately, as this is an intermittent short, checking resistances with an Ohm meter for a short may not prove fruitful. You will likely find success with visual inspection of wires where they run out of a harness to a light or near the chassis (muffler). Good luck.

    Jim S.
     
  5. LSU348

    LSU348 Formula 3

    Dec 19, 2003
    1,047
    Sugar Land
    Full Name:
    Mike
    #5 LSU348, Jan 9, 2004
    Jeeez...good point. Are you looking under my garage door? It did work for a bit then boink! Dead light. I will cut straight to the line check.
     
  6. brent Lachelt

    brent Lachelt Formula 3
    Silver Subscribed

    Dec 6, 2003
    1,828
    Brownsburg, INDIANA
    Full Name:
    Brent R.Lachelt
    #6 brent Lachelt, Jan 9, 2004
    I had something similar on my 308. I don't remember if it was the RF and LR or LF and RR, but it was the fuse that controls that and the license plate light. Turned out it was a old rusted, exposed, pinched wire in the rear deck lid that was going to those license plate lights. I would remove those lights and check the wires. As I recall I needed a ground too. Had a similar problem with the front right turn signal. Again a pinched wire.
     

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