power windows relay

Discussion in 'Automotive Electronics' started by qwwe, Feb 21, 2019.

  1. qwwe

    Thread Starter New Member

    Jul 18, 2017
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    Hi
    They usually use relays to improve power Windows performance .
    But the question is, if the contact of one of the relays is attached, it will be permanently connected to the motor, which is controlled by the h-bridge and the direction it changes, and thus the motor is damaged.Because Windows is at its highest, but the motor is still trying.
    Is that the same?
     
  2. AlbertHall

    AAC Fanatic!

    Jun 4, 2014
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    Should this be in 'automotive'?
     
  3. MaxHeadRoom

    Expert

    Jul 18, 2013
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    The windows on my GM have an electronic breaker that switch off automatically when the motor is fully up or down and the power is still applied.
    Max.
     
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  4. cork_ie

    Active Member

    Oct 8, 2011
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    I'm not quite sure what your question is .
    Are you asking what would happen if the NO contacts on one of the relays stuck closed when the window was fully up or down?
    Can you give us a wiring diagram or schematic of your electric window system, real or theoretical ?
     
  5. iONic

    AAC Fanatic!

    Nov 16, 2007
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    Essentially you are trying to make a "logical" connection between a BAD relay and a BAD window motor. Yes???
    Or is there other insight requested?
     
  6. qwwe

    Thread Starter New Member

    Jul 18, 2017
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    This is the circuit:

    Is this the circuit of the said problem?
     
    Last edited: Feb 22, 2019
  7. cork_ie

    Active Member

    Oct 8, 2011
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    You can supply your power to the up & down relays, through a third "safety relay" that is only powered when the switch is operated in either direction. In this case you will eliminate the risk of burning your motor. The chances of two relays having their contacts weld together at exactly the same time , are considerably less than being hit by a meteorite.
     
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  8. Reloadron

    Distinguished Member

    Jan 15, 2015
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    Can't speak for others but the windows on my 2007 GMC Yukon Denali stop at the end of travel up or down. Something else they do is if there is an overload they have a thermal circuit breaker. This being winter in NE Ohio, USA my windows occasionally will freeze till the truck warms up. If I try to lower a window which is frozen with ice after a few tries jerking it up and down it will quit responding for a short period of time. That leads me to believe they have a thermal circuit breaker in there somewhere. It senses the heavy load of the motor in a stall and that's it.

    Ron
     
  9. MaxHeadRoom

    Expert

    Jul 18, 2013
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    See #3. ;)
    Max.
     
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  10. Reloadron

    Distinguished Member

    Jan 15, 2015
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    That would be it! :)

    Ron
     
  11. iONic

    AAC Fanatic!

    Nov 16, 2007
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    I think the answer is likely NO. A bad relay should not cause a bad motor.
     
  12. qwwe

    Thread Starter New Member

    Jul 18, 2017
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    It seems to you that when the Windows reaches its peak, an increase in the engine current, such as when the motor stops, does not burn the fuse and thus protect the motor.
    I mean, the contact of one of the relays affects the motor as a result of the operation.
     
    Last edited: Feb 25, 2019
  13. KeepItSimpleStupid

    AAC Fanatic!

    Mar 4, 2014
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    Both relays on is the equivalent of OFF/BRAKE, just a different version.

    I know the windows on my car have a thermal. They won't work if it too hot outside/inside. I had it happen once or twice.
    I suspect it's there for protection, but just ambient temperature, very hot day and a car in the sun did it.

    On another vehicle frozen windows you might hear a jerk for a short time when the window can't move.
     
  14. cork_ie

    Active Member

    Oct 8, 2011
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    In the event of a relay contacts sticking together, as the OP seems to be suggesting , it is quite possible.
    A thermal cut out, if fitted may offer some protection but this can only cycle so many times before it gets damaged too. Unfortunately; any repair inevitably involves dismantling the door and motor.
     
  15. cork_ie

    Active Member

    Oct 8, 2011
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    I was not referring to both up & down relays, I was referring any one of these directional relays and the proposed "Safety relay"
    Most modern systems do not have a thermal cut-out as they are fed via a module in the door with built in current sensing . The system the OP describes is more basic.
     
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