Short Circut

Fred
Fred Expert Adviser
edited November -1 in HUDSON
Any suggestions on this one. Jethroe the 46 Hudson Pickup has decided to blow fuses in the headlight circut.. I ran a hot wire from battery to posts at side of radiator and High low and parking lights all work. When I push the switch once (parking lights) fuse blows. I ran a new lead from fuse to switch: fuse blows. I didn't mess with dimmer switch as parking lights blows fuse. I was thinking of wrapping fuse in tinfoil and watching for smoke, but thought better of it and decided to ask for suggestions

Thanks,

Fred

Comments

  • Unknown
    Unknown
    First off, forget the tin foil. If fuses keep blowing, you must have a short to ground. You might want to try rewiring back to original. Then, install a headlight relay under the hood to take the load off of the switch.
  • Unknown
    Unknown
    Sounds like a short in wire between fuse and the post at side of radiator for the parking lights , try a nrew wire there --BUD
  • Unknown
    Unknown
    I believe the parking lights are a add on. 47 pick came without parking lights except the center grill light and had 1 tail light that came on with the first click of the light switch. Also dash lights came on. I would start looking at the under dash wireing then from the fire wall plug to the junction block on side of radiator. Dont remember just how the tail light wires but think in a harness with the tail, stop light and gas sending wire together. So I would start at the tail light looking forward for a bad wire.
  • Fred
    Fred Expert Adviser
    Thanks Guy's. So far I have eliminated headlights as the problem. Also rewired tail lights seem OK. So I'll be sticking my head under the dash hoping to see something. Of course I just installed the radio, so as pogo would say "I have found the enemy and it is (probably) us".

    Fred
  • RL Chilton
    RL Chilton Administrator, Member
    Fred-



    Don't know who "pogo" is, but I know that saying all too well . . . happens to me all the time.
  • drivergo2
    drivergo2 Expert Adviser
    Did you have the short before the radio was installed or after ?:confused:John drivergo2
  • Geoff
    Geoff Senior Contributor
    Try disconnecting the wire that goes to each circuit from the switch, one at a time until you find which one is causing the short. My bet is in the tail light somewhere. You will find something has pinched the wire and caused a short to ground.
  • Fred
    Fred Expert Adviser
    drivergo2 wrote:
    Did you have the short before the radio was installed or after ?:confused:John drivergo2



    After: that's why I think the Enemy is me. Pogo was a cartoon Character in the comics a few years ago. I believe he was Pogo Possum
  • mars55
    mars55 Senior Contributor
    And here the Possum himself.



    images?q=tbn:hba8__rsFYfXIM::papundits.files.wordpress.com
  • Fred
    Fred Expert Adviser
    I'm Glad Pogo is entertaining everyone, but he isn't much help in finding the short circut.

    Fred
  • [Deleted User]
    [Deleted User]
    If only the parking lights are causing the problem. Start at the parking lights and work backward towards the switch. Check wiring for scrapes, melted coverings etc. or disconnect the Parking light wire from the switch and from the terminal block next to the radiator, take an Ohmeter and check for continuity from the end of the wire to ground. If the wire is shorted to ground it will show continuity.
    In all probability if you did not have the problem before the radio install you may have pinched a wire when putting the radio in.

    Bob
  • Fred
    Fred Expert Adviser
    BJ__TN wrote:
    If only the parking lights are causing the problem. Start at the parking lights and work backward towards the switch. Check wiring for scrapes, melted coverings etc. or disconnect the Parking light wire from the switch and from the terminal block next to the radiator, take an Ohmeter and check for continuity from the end of the wire to ground. If the wire is shorted to ground it will show continuity.

    In all probability if you did not have the problem before the radio install you may have pinched a wire when putting the radio in.



    Bob



    Maybe I'm forgetting something from my 1940's High School Electric class but this is where I'm at. New wire from fuse block to switch "B" terminal. Wire to "L" terminal connected to switch works headlights, no problem. Wire to "T" terminal blows fuse when connected. Ohm meter connected to ground (earth for Geof) and "T" wires (2) moves needle all the way to right (no resistence?) BUT Ohm meter to "L" wire (off switch) also moves needle to right? I realize problem is located in tail light/parking light circut, but why does "L" circut also show no resistence?

    Fred
  • Unknown
    Unknown
    Maybe because unless you dont have the head lights unpluged. Also are you sure it shows no resistence. On my meter if the needle moves to the right it is showing resistence. If dont move no resistence.
  • nick s
    nick s Senior Contributor
    Fred, the grille light should be part of the taillight circuit. Did you replace it as well?
  • [Deleted User]
    [Deleted User]
    OK Do not check for resistance, check for continuity.
    Even a straight length of wire has some resistance if the meter is set low enough.
    If the Wire to the T terminal blows the fuse, disconnect it from the switch and check from the end of the wire to ground. You may have to remove the bulbs from the park lamps and taillights then there should be NO movement of the needle if the meters needle moves there is a short. Then you have to find where the short is.
    Bob
  • Geoff
    Geoff Senior Contributor
    The problem with checking for continuity is that the bulbs have very little resistance when cold. As BJ mentions, remove all the bulbs. Then check for continuity between ground and each circuit. With all the bulbs out you should have no reading on a good circuit. If one of the wires is shorted, you will have a zero resistance reading.
  • Fred
    Fred Expert Adviser
    I want to sincerely thank you all for the suggestions. Yesterday I finally found the culprit. 1. I belive my meter is defective as it shows continuity when there is none. 2. I became so frustrated I decided to do the "smoke test". I ran a hot wire to the parking light circut: and, low and behold, the parking lights lite (no smoke) I wired the circut through the switch and blew a fuse. I changed the switch to a spare I had and "wallah" all is well. Defective switch!
  • [Deleted User]
    [Deleted User]
    Congratulations Fred, finding a short can be one of the hardest things to do. Keep up the good work.
    Bob
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