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Turn radio on and watch what happens???

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 85 Shortbox, May 2, 2002.

  1. 85 Shortbox

    85 Shortbox 1/2 ton status

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    Yesterday I turn my radio on and watch the voltimeter and oil pressure gauge go down. The truck didn't run any different so I am wondering if something is affecting just the gauges and not neccesairly my oil pressure or amount of electricity. I should mention this is in my daily driver 92 S-10.
     
  2. mudober

    mudober Registered Member

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    Check your alternator with a voltmeter conected to your battery.With your eng. running it should be between 13 &14 volts, now turn on your stereo if it drops to 12 or less your stereo is drawing exsessive current causing eng rpm to drop therfore oil pressor lowers.Maybe you have a bad cell in your battery too.
     
  3. dyeager535

    dyeager535 1 ton status Premium Member

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    Your radio definitely shouldn't be drawing that much juice unless you've got some serious system in there. I'm guessing this is an aftermarket radio? I really don't have any leads on what could happen to cause this though, the radio shouldn't be hooked to the trucks wiring system except to get the voltage, maybe power antenna, and ground.

    If the oil pressure gauge is moving, unless engine RPM's are actually dropping too, that tells me that somewhere a wire is messed up that somehow ties the radio and volt/oil gauges together, or the radio *is* drawing that much, (again you'd have to have some serious stereo going for that to happen) and the alternator isn't able to handle the load.

    My 78amp alternator doesn't fluctuate at all when I turn the stock radio on.
     
  4. TwoCrowsDesign

    TwoCrowsDesign 1/2 ton status

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    My wife's 89 S-Jimmy does the same thing, plus when she opens the doorthe radio loses power, and the dome light won't go off when the door is closed. It just gets curiouser and curiouser...

    I suppose I have a weekend of electrical troubleshooting in my future...
     
  5. dyeager535

    dyeager535 1 ton status Premium Member

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    Sounds like *your* problem is the door jam switch(es) I forgot the radio has two power leads, 12v constant, and 12v ignition. Or at least they do on the 80's digital radios. Presets/clock need constant 12v, the radio gets ignition 12v (no radio without key)
     
  6. Blazer1970

    Blazer1970 1/2 ton status

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    Ha, ha, have fun with that troubleshooting. One time when I was at the dealer, I saw a new S10 Blazer with the ENTIRE interior removed - I mean seats, carpeting, headliner, door panels, side panels and the dash. They had the whole wiring harness exposed trying to troubleshoot some kind of weird electrical problem. I bet that thing had a few extra squeaks and rattles when they got it back together!
     
  7. 85 Shortbox

    85 Shortbox 1/2 ton status

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    Ok a little more info... It is the stock deck. I removed the aftermarket deck I had in it because ever since my truck was broken into and the deck was pulled half out of the console, it had been acting stupid. I put the stock deck back in and the same thing happens. Also when I turn the headlights on this also happens. Could a bad ground be causing this problem???
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    The only way the headlights *should* be tied to the radio is if the radio has either a dimmer function, or a lighted display for when the headlights come on. Since you swapped decks, was wiring done correctly, soldered and shrink wrapped for instance?
     
  9. 85 Shortbox

    85 Shortbox 1/2 ton status

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    It is all the factory wiring harness. The panel lights which come on when you turn on the headlights do have a dimmer switch that is tied into the radio. THIS SUCKS!!!
     

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