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  1. #1
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    test switch for Latched or pulsed

    How do you test a circuit to see if it's latched or pulsed. Mainly Rear defrost on 04 Dodge Intrepid. I think I figured it out but would like someone to confirm...

    Pulsed: when I press the button to activate the rear defrost it sends out a quick pulse to activate defrost relay (negative pulse into a positive system) this would cause the voltage to drop quickly and briefly from 12v +

    Latched: When I press the button it sends out a steady negative current to drop the voltage from 12v + for a duration (10min) then turns off and voltage resumes to 12v+

    Is this correct?
    Last edited by Car_modifier; 25th September 2012 at 05:34.

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  2. #2
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    Re: test switch for Latched or pulsed

    i would think that there is a timer module. When you press the switch, you put a pulsed earth on an input to the timer. The timer then runs and turns on a local light (LED?) and a big switch to connect the battery + to the screen heater. When the timer runs out it it switches every thing off. I hope this helps
    Frank



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  3. #3
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    Re: test switch for Latched or pulsed

    Quote Originally Posted by chuckey View Post
    i would think that there is a timer module. When you press the switch, you put a pulsed earth on an input to the timer. The timer then runs and turns on a local light (LED?) and a big switch to connect the battery + to the screen heater. When the timer runs out it it switches every thing off. I hope this helps
    Frank
    Didn't help... just want to confirm my above post as to the discriptions of a pulsed or latched system...only got a volt meter to workwith.



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  4. #4
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    Re: test switch for Latched or pulsed

    If the switch is latched then you need to push it again to unlatch it. Measure its contacts for a voltage, then push the switch if the voltage changes, then goes back when the push the switch again, its a latching switch. Check all contacts with the button pressed at least 3 times. if all you see (or might not see)is a glitch on your voltmeter when you press the switch then its a momentary contact type. The pulse may be too fast to register on a voltmeter.
    Frank


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  5. #5
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    Re: test switch for Latched or pulsed

    Thank you +1 rating



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