Idiot light brakes problem

Discussion in 'Technical' started by the muss, Jul 25, 2016.

  1. the muss

    the muss Member

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    So all my idiot lights work exept the brakes light. I've read That it is supposed to light up like the temp light when cranking the engine. It doesnt. I grounded the wire at the switch With the brake lines and it comes on. So bulb is working. Where do i look for the wire That is making it light up when cranking the engine. Been Reading up and down on the forum but Cant find anything about That light.. this light is critical That it works when i show the car to get license plates.
     
  2. Crazy Larry

    Crazy Larry Member

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    If it lights up when the brake pedal goes all the way to the floor, it's working correctly. Of course you can't know that unless you open a brake line bleeder while someone depresses the pedal. Obviously, it's lighting when you ground the switch, so perhaps you have a bad ground to the light in the circuit.
     
  3. 71gold

    71gold Frank Cooper Supporting Member

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    :scratchchin:...I'm not thinking that's how the light works. I wouldn't think you would need a light to tell you your brake pedal is on the floor.
    I think it's for if front to back has a low fluid situation the plunger would bias to that side and then the light would come on. JMO
     
  4. the muss

    the muss Member

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    My problem is that it dont light up when it crancks like it is supposed to do. Its to check That the light works. I Cant tell the mechanic That is going over the vehicle to bleed the line to see if the light comes on? He Just checks That it comes on when cranking the engine. If it doesnt i dont get my license plate before it is fixed.
     
  5. Krazy Comet

    Krazy Comet Tom

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    Brake light illuminates IF there is a 225 PSI differential in front vs rear pressure(moves switch off center completing ground circuit)... Amount of fluid has zero to do with illumination...

    Also lights when cranking via a ground contact from black wire in ign switch to Violet wire...

    If it lights by grounding violet wire(which is same point as on pressure switch), either ground to ign switch or switch itself is defective

    [​IMG]
     
  6. the muss

    the muss Member

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    Thank you since the temp light is coming on i guess it is the violet wire That is defective i will check That tomorrow. Thanks.
     
  7. Krazy Comet

    Krazy Comet Tom

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    The temp light ground from switch when cranking is red/white wire directly to right of violet wire... I didn't snip enough to show color...

    Since brake light lit when grounded under hood, I'll bet the ign sw has a internal issue... May be poor connection on switch connector...
     
  8. mav man

    mav man Member

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    I don't think it comes on when starting just if there is a brake problem
     
  9. Crazy Larry

    Crazy Larry Member

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    Seriously Frank, it's a stupid design. On modern cars, the light comes on when you lose hydraulic pressure, even is the brakes seem to be working fine and the pedal feels fairly firm. The Maverick Brake light doesn't come on until the pedal literally bottoms out. Like, "duh", it's too late. Pretty obvious when the pedal hits the floor that there a brake problem. But that's how these old cars are.
     
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  10. Mavman72

    Mavman72 Gone backwards but lookin' forward

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    What larry said...
    Hence the term "Idiot" light
     
  11. yellow75

    yellow75 MCCI Oregon State Rep Supporting Member

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    When a line loc is installed ahead of the proportioning valve or distribution block what ever you want to call it the brake light will come on until you release the line loc switch. The brake pedal is not on the floor then, the valve senses differences in pressure between the front and rear brake bias. I have had 2 different 72s one with disc brakes and one with drum brakes that this event happens with. And yes the brake light in dash does come on when key is first turned on
     
  12. the muss

    the muss Member

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  13. Grabber-1

    Grabber-1 Member

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    What was the cure?
     
  14. the muss

    the muss Member

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    Hehe well i really dont Know.. after grounding it to check that the bulb worked, it works. Maybe it Just needed a bump hehe. Its probably a bad ground somewhere. But for now im happy
     
  15. Crazy Larry

    Crazy Larry Member

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    Well, my Brake light has never come on until the pedal was all the way to the floor. So much for sensing pressure differential if it can't sense it before the pedal bottoms out.

    But yes, it should light when cranking the engine, just like the Temp light.
     
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