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1.5 Amp Fuse keeps blowing in my car

Discussion in 'Electronic Design' started by [email protected], Mar 11, 2007.

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  1. Guest

    I have a GPS set up in my car - Basically I use a power outlet in the
    dash similar to a cigarette lighter with a splitter to feed 2 12V
    items items. My setup includes an HP Ipaq that has a 5 amp fuse -
    never blows a fuse into 1 side of the splitter. The other side for
    about 5 months I plugged in my GPS Bluetooth receiver - It recently
    keeps blowing the 1.5 amp fuse. I even bought a new charger. I can the
    take the charger whcih similar to a cell phone charger and put it into
    another vehicle & it will not blow the fuse. My GPS receiver requires
    the 1.5 AMP fuse. I would imagine there is something in the circuitry
    of my vehicle causing it to blow 1.5 Amp 250V fast acting fuse - is
    there anything I can put on the circuit to ro stop this ????
     
  2. On 11 Mar 2007 16:36:09 -0700, in sci.electronics.design
    You could possibly measure the current, or is that a bit technical?


    martin
     
  3. Guest

    With a little direction I can do it - I have 3 meters bascially your
    39.95 type but I'm sure I can do it - what do I set my meter to when
    you say measure the current -

    Thanks
     
  4. no_one

    no_one Guest

    put in a 3 amp fuse. The splitter seems to be able to handle it and you
    won't be plagued with nuisance blowouts. If the GPS is truly failed it will
    blow the 3 and you will need to troubleshoot the GPS unit. Otherwise the
    upstream wiring should be just fine.
    many people seem to believe that fuses are to protect the load device when
    they are really to keep the upstream wiring from burning up.
     
  5. Guest

    Actually what I failed to mention was I plug the charger in to the 12V
    power outlet without plugging the other end into the GPS and it blows
    the fuse - it has something to do with the power source in my car not
    the GPS unit - in other vehicles it does not blow the fuse

    Thanks
     
  6. It seems like the charger is causing a momentary surge, possibly because of
    a capacitor charging up. The vehicle that does not cause a problem may have
    some sort of series resistance or inductance that limits this surge. It
    would be difficult to measure this surge without a storage scope or peak
    reading meter. You should be able to use, perhaps, a 1 amp slow blow fuse.
    You could also add maybe a 1 ohm resistor in series, or a hash choke. There
    are also surge limiting thermistors that start at a couple of ohms and then
    drop to about 1/10 that when they get hot.

    Paul
     
  7. Guest

    I will try both - 2 questions - Can I use a 1.5 Amp slow blow or did
    you recommend a 1 AMP slow blow instead of 1.5 for a reason. Also when
    you say in series can I simply put a 1 ohm resistor on the + positive
    side of the female power outlet the charger plugs into

    Thanks
     
  8. The 1 amp gives a better safety margin, but 1.5 amps should be OK. The
    wiring will be protected in either case.

    The resistor would go between the 12 VDC source and the outlet. The fuse
    would also be in series. If you disconnect either the fuse or the resistor,
    the circuit will be open.

    Also, make sure the power plug does not somehow short out the connector as
    it is being inserted. Especially if it is not a standard type connector for
    12 V power.

    Good luck,

    Paul
     
  9. A slow blow fuse?



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  10. Guest

    Paul thanks for your time & help

    I will try both
     
  11. That might not be very helpful. Your meter might be able to measure the
    steady state draw of this charger. But I suspect that what is blowing
    your fast acting fuse is the charging current of a capacitor in its
    input stage. You'd need an oscilloscope to see that.

    Try replacing the 1.5 A fast acting fuse with a slow blow type (same
    rating).
     
  12. Eeyore

    Eeyore Guest

    If the fuse blows it's because the current is too high !

    What's the spec of the GPS receiver ? What model even ?

    Graham
     
  13. Eeyore

    Eeyore Guest

    My thoughts entirely.

    Graham
     
  14. w_tom

    w_tom Guest

    Better is to cure the 'power on' surge with a component called an
    'inrush current limiter'. It starts with higher resistance, then
    resistance goes lower. Inrush current limiters are standard and
    plentiful for 120 volt appliances (that have lower current draw).
    They may be harder to find for your higher current. If not an inrush
    current limiter, then Paul Hovnanian's slo-blo fuse recommendation is
    a better solution.

    Also a warning. Some 12 volt plugs short out (therefore blow any
    fuse) when put in some 12 volt auto power receptacles.
     
  15. colin

    colin Guest

    reminds me of a myth on mythbusters about someone replacing a blown fuse
    with a bullet ....

    Colin =^.^=
     
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