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Relay-ing your brakes lights

Discussion in 'The Hokey Ass Message Board' started by cosmo, May 2, 2013.

  1. d2_willys
    Joined: Sep 8, 2007
    Posts: 4,094

    d2_willys
    Member
    from Kansas

    Why not just put a nice 1uf capacitor across the hydraulic switch? That will help with the arcing phenomenon, just like the condenser across your ignition points. Simple!!
     
  2. mustang6147
    Joined: Feb 26, 2010
    Posts: 1,848

    mustang6147
    Member
    from Kent, Ohio

    I have never had a failure..... Atleast not in my brake lights.... But anything mechanical can fail that's for sure..... And us guys that are mechanical continue to improve things as well....
     
  3. Kona Cruisers
    Joined: Feb 4, 2007
    Posts: 1,071

    Kona Cruisers
    Member

    Just so you know... Hyundai has the lowest warranty event per unit sold then any mass made vehicle For 5 out of 6 years... That includes BMW and the European lot...

    (and I work for GM.)
     
  4. Well, 'glad' to see so many interested in pointing out why they won't be dong this.

    Note to you all: I didn't post this for you.

    Now, as to the naysayers:
    1) If relays failed as often as you indicate, I would never make it to work, as there would be nothing but dead cars from here to there.
    2) A relay has a greater amp capacity than a brake switch. Therefore, this makes sense in a current-carrying way. And if you were to ever tow anything, this takes the load.
    3) It does actually hurt a bit when I am attacked for posting tech. There are damn few places where anyone can learn this stuff, and if you shove those who CAN teach off due to silly/stupid/unecessary comments, well, where WILL you go for tech?
    This particular mod adds safety with no drawbacks, esp. in the case with hydraulic switches, which gradually fail (mostly) in a manner which leaves doubt as to whether they are working or not. A relay can at least be heard (engine off), which ADDS safety.

    So, if you do not wish to peform this modification, please do not, and no need to tell anyone, either.

    Cosmo
     
  5. Fenders
    Joined: Sep 8, 2007
    Posts: 3,922

    Fenders
    Member

    X2, I have always had a mechanical BL switch on my pedal.
     
  6. DD COOPMAN
    Joined: Jul 25, 2009
    Posts: 1,123

    DD COOPMAN
    Member

    Cosmo...Great point(s), and well-put. Unfortunately, as I'm sure you're well-aware, SOME dedicated "nay-sayers" will never be convinced of the benefits of "SLICED bread"! Great TECH article. DD
     
  7. Of course, you could just go to LED bulbs and reduce the load on the entire circuit that way. Not traditional, though.
     
  8. gimpyshotrods
    Joined: May 20, 2009
    Posts: 15,662

    gimpyshotrods
    Member

    I run relays on just about every circuit.
     
  9. buzz4041
    Joined: Nov 14, 2008
    Posts: 213

    buzz4041
    Member
    from Texas

    Good write up. I have put a relay on this circuit for exactly for the reasons you described. Reduce the load on a hydraulic switch.
     
  10. Mike51Merc
    Joined: Dec 5, 2008
    Posts: 3,758

    Mike51Merc
    Member

    You shouldn't be offended, at least not personally. You took the risk of posting an idea on a forum and it could go either way, but your risk is appreciated. Some days you're a hero, other days not so much, but your participation matters either way. You can't expect only positive comments and the naysayers to remain silent otherwise nobody would ever really learn anything.

    Suppose somebody posted a REALLY bad idea and everybody stayed silent?
     
  11. 117harv
    Joined: Nov 12, 2009
    Posts: 6,580

    117harv
    Member

    I'm not electrical savy, what does a relay do? I read all the posts and it doesn't say what is does?
     
  12. ev88f
    Joined: Jan 29, 2010
    Posts: 371

    ev88f
    Member

    Basically it handles the switching of the power using the actual switch as just a trigger. Setting it up this way would make your actual switch last forever and create a pretty bulletproof setup.

    Same theory behind guys using an msd box for a points distributor, taking voltage away from the switch.
     
  13. 117harv
    Joined: Nov 12, 2009
    Posts: 6,580

    117harv
    Member

    Thanks for the explanation, I get now.
     
  14. Don's Hot Rods
    Joined: Oct 7, 2005
    Posts: 8,319

    Don's Hot Rods
    Member
    from florida

    While adding a relay isn't going to hurt, I am going to go with the guys who said " why do it". There isn't enough load to warrant one, even if you plumb in for something like trailer lights. I've never used one on any of the numerous cars I have wired, nor has any of my stockers had one, so I just don't see the point of adding one.

    Fan relay, yes. High and low beam relay, yes. Electric fuel pump relay, yes. But I don't think there is a reason for one on the brake lights.

    Don
     
  15. BootleggerMatt
    Joined: Aug 17, 2011
    Posts: 258

    BootleggerMatt
    Member

    Cosmo, neither your post nor your reply above make any sense to me. Not that you are one, but we can't have idiots "teaching" people and have the ones that really know how to do it keep their mouth shut because they don't want to offend that guy.
     
  16. Cosmo, I resisted replying to this thread because I know that you are providing what you believe is useful information. From your perspective it is. From mine it is just another component to fail.

    I am a retired mechanic and brake light switch failure has never been epidemic. Maybe the problem is people buying switches from catalog type suppliers that buy from the cheapest source possible. A good name brand switch should last for many years.

    The contacts that were originally spec'ed on these switches were ample to carry the load and were as robust as those on this type of relay.

    I believe it keeping it simple! Buy good parts.

    ~Alden
     
  17. Mike51Merc
    Joined: Dec 5, 2008
    Posts: 3,758

    Mike51Merc
    Member

    Just another note---- old pressure-style brake switches are prone to failures from DOT 5 fluid.
     
  18. Don's Hot Rods
    Joined: Oct 7, 2005
    Posts: 8,319

    Don's Hot Rods
    Member
    from florida

    I'm in total agreement with Cadzook, you posted this thread with good intentions and just wanted to pass along some information you thought was helpful. Thank you for doing that. But by questioning the necessity for this add on we weren't being disrespectful, just trying to give another viewpoint that it might not be needed.

    I've posted things where people took exception with it and while it is never pleasant to have that happen it is just part of the forum experience. Don't let it hurt your feelings and certainly don't let it keep you from passing along other things you feel might be helpful. :):) Like everything else that is posted, a person can accept or reject it for their own uses.


    Don
     
  19. rfraze
    Joined: May 23, 2012
    Posts: 1,983

    rfraze
    Member

    Teaching how to wire relays IS a good thing and Cosmo's post was very simple to follow. A couple of other points could help. Either wire 86 or 85 can be switched to trigger the relay. Cosmo showed 86 as a + connection, so if you are triggering from a switch that supplies positive current, connect the wire here to provide current to the + side of the switch. Remember, the fused power should go in to 30, in this case protecting the brake light circuit. Cosmo described switching the 85 or negative side, which obviously works.
    Another smart use of a relay is as a remote switch. Place it near the load, and hopefully near a source of power. Then the long run of wire from the switch can be a smaller wire and either positive or negative.
     

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