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Thread: E21 hazard switch

  1. #1
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    E21 hazard switch

    My hazard switch popped out (surprise surprise) and drained my battery overnight, though amazingly the hazards themselves were still blinking slowly. I removed the switch to prevent further drainage.

    My question to you all is: Will the hazard switch need to be connected in order for AAA to help jump the car?

  2. #2
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    No, I don't believe so...but I could be wrong. I believe it only runs blinkers and hazards. Someone correct me if this isn't right.

    In the FAQ section of this forum, you can see how to fix your hazard switch. It just needs to be split at the two molded pieces, then an arm needs to be gently bent in ever so slightly. It's free and will give that switch a few more years of life. Checkout the write up. Though from your expectation of this problem, you probably already know this. lol
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  3. #3
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    You can certainly start the car without the hazard switch connected, but once you have the car jumped and running, you'll need to have the hazard switch back in place to use many of the car's electrical functions; turn signals, heater fan, horn, etc.

    As a temporary fix, you can plug the switch back in place as normal, then wedge a toothpick or paperclip into the gap around the red button while holding it in the closed position. That will keep it from popping out until you get time to disassemble it and fix it properly (or replace it).

  4. #4
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    Dude, the Hazard is ALL. If you unplug it you will find that the entire car will cease functioning, the planet will slowly stop spinning and while that is happening all the missing left socks will appear in your glove box.

    Keep it plugged in and stick a folded piece of paper wedged just under the button (some use a paper clip) to keep it in the right position until help arrives.
    I still drive daily with no commute...
    The Hazard is All, Praise the Hazard!



  5. #5
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    dumbclub is right. I have a trusty screw jammed in place to keep mine from popping out again. Just a temporary fix, but does the job.
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  6. #6
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    Quote Originally Posted by dumbclub View Post
    you'll need to have the hazard switch back in place to use many of the car's electrical functions; turn signals, heater fan, horn, etc.
    I find most of these 1st world country amenities optional... Lol, kidding....
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  7. #7
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    Electricity is such a bourgeois concept.

    I drove without my hazard switch unplugged one morning (when it broke on me and before I could search for a fix) and was freaking out that I couldn't use my turn signals. I don't know how 80% of America drives like that.

  8. #8
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    Right??? Geez I swear I hate SoCal because NO ONE uses blinkers. As a matter of fact, if I'm at a four way at the same time as another person (I'm going straight, they're turning left across from me), I always watch out because they often don't signal. Then I usually put my hands in the air and yell "Where is your turn signal?" To date, I see no wide-spread social improvement using this educational tactic.
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  9. #9
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    so what happens if turn signals work and everything else works BUT that hazard? mine doesnt work and the previous owner i dont think even bothered with it after everything he has done to the car. i asked him about it and he simply said: "youll never get the hazard to work". i thought to myself yea right he must have just not messed with it. so i do want that to work as for me its pretty important, that and my horn doesnt work. so the times i needed it is well too many times here in CA lmao

    Quote Originally Posted by zohanisback View Post
    Right??? Geez I swear I hate SoCal because NO ONE uses blinkers. As a matter of fact, if I'm at a four way at the same time as another person (I'm going straight, they're turning left across from me), I always watch out because they often don't signal. Then I usually put my hands in the air and yell "Where is your turn signal?" To date, I see no wide-spread social improvement using this educational tactic.

    god god man its everywhere in CA noone likes using blinkers, and i cant honk but thank god my brakes are still good. i dont know why people jsut dont as many accidents have occurred. i always use them. have to. i always play the "safer than sorry" card
    Last edited by Axuise; 02-01-2013 at 02:54 PM. Reason: Automerged Doublepost

  10. #10
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    Haha, funny when people do that... Just give up.

    To be honest, I am not totally sure about this one. I can't help but wonder if there is maybe the switch connections are bad if the blinkers work. I don't think there is a separate relay for hazard and blinker. I believe it is just one. So if blinkers work, maybe poor connections when the hazard is out (on position)?
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  11. #11
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    almost wonder if i can make my own hazard type switch with blinker circuit board as a bypass maybe!? dunno if that makes much sense or even possible in a way but would be awesome to make.

  12. #12
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    the hazard light switch curse just got me! the red plastic cover fell off hazards came on... I'm now using the trusty screw method to keep the switch positioned so the hazards are off and my turn signals function. would like to find a used one does anybody know if the same switch was used in any other series? that would work on my 83 320i?

  13. #13
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    okay guys listen up and I'll expell all myths concerning the 'hazard'. below is for my 77, the post facelift is pretty much the same.

    fuse #15 sends power to both the hazard switch to power the turn signals AND the windshield wiper motor. if the fuse blows it will kill both the wipers and the turns, but a mis-functioning hazard will not affect the wipers.

    fuse #17 also sends power to the hazard, through it when switched on and then to the four way flashers.

    with the hazard lights off, power from the wipers run through the hazard swithch to the flasher relay, then to the turn stalk and on to the turn lamp and to ground.

    when you push the button and turn on the flashers the switch shuts off the power to the turn signals and turn on powers to the hazards. so in other words, it switches off power from fuse 15 and turns on power from 17.

    so you push the button and turn on the blinkers. power from fuse 17 is fed through the switch to the turn signal relay, through the relay and back to the switch, that power now alternating on and off by the relay is sent directly to the four bulbs and then ground bypassing the turn stalk.

    that's it. the hazard has nothing to do with anything else. not the radio or the horn. not the ignition or the back up lights. nothing but the wiper motor and really it's just sharing the fuse so unless the switch causes the fuse to blow it doesn't even effect the wipers. BUT, fuse 17 also feeds power to the interior/glove box lights so if fuse 17's circuit is bad it will kill the interior lights and the turn indicators but the problem is not cause by the hazard switch.
    Last edited by Tom D; 02-02-2013 at 08:20 PM.
    Tom D

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  14. #14
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    Quote Originally Posted by Tom D View Post
    okay guys listen up and I'll expell all myths concerning the 'hazard'. below is for my 77, the post facelift is pretty much the same.

    fuse #15 sends power to both the hazard switch to power the turn signals AND the windshield wiper motor. if the fuse blows it will kill both the wipers and the turns, but a mis-functioning hazard will not affect the wipers.

    fuse #17 also sends power to the hazard, through it when switched on and then to the four way flashers.

    with the hazard lights off, power from the wipers run through the hazard swithch to the flasher relay, then to the turn stalk and on to the turn lamp and to ground. I think that BMW feels that your most likely to use the hazards if its raining and therefore if the wiper's fuse is good, then so are the hazards.

    when you push the button and turn on the flashers the switch shuts off the power to the turn signals and turn on powers to the hazards. so in other words, it switches off power from fuse 15 and turns on power from 17.

    so you push the button and turn on the blinkers. power from fuse 17 is fed through the switch to the turn signal relay, through the relay and back to the switch, that power now alternating on and off by the relay is sent directly to the four bulbs and then ground bypassing the turn stalk.

    that's it. the hazard has nothing to do with anything else. not the radio or the horn. not the ignition or the back up lights. nothing but the wiper motor and really it's just sharing the fuse so unless the switch causes the fuse to blow it doesn't even effect the wipers. BUT, fuse 17 also feeds power to the interior/glove box lights so if fuse 17's circuit is bad it will kill the interior lights and the turn indicators but the problem is not cause by the hazard switch.
    Right On!

    I'm printing this and placing in my binder.

    Thank you
    2011-E90 328i 6 speed manual.

  15. #15
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    Quote Originally Posted by sicalps82 View Post
    My question to you all is: Will the hazard switch need to be connected in order for AAA to help jump the car?
    Let's review.
    1. Looks like everyone agrees that it is not necessary to reconnect the hazard switch in order to jump the car.
    2. A lot of us believed that the hazard switch is the center of the e21 universe and that disconnecting it brings about an abrupt and apocalyptic end to the flow of electrons in our solar system.
    3. Tom D has restored order by employing his preternatural ability to decipher an electrical schematic and put it in simple enough terms for the rest of us to understand.

    My memory has failed me again. I was so sure that next to nothing in the car would work with the hazard switch unplugged, I went out and removed mine to verify. Turns out that the turn signals are the only thing that didn't work. Horn was fine. Wipers were good. Heater fan normal.

    Thanks Tom. Another e21 urban myth - busted!

  16. #16
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    Quote Originally Posted by Tom D View Post
    okay guys listen up and I'll expell all myths concerning the 'hazard'. below is for my 77, the post facelift is pretty much the same.

    fuse #15 sends power to both the hazard switch to power the turn signals AND the windshield wiper motor. if the fuse blows it will kill both the wipers and the turns, but a mis-functioning hazard will not affect the wipers.

    fuse #17 also sends power to the hazard, through it when switched on and then to the four way flashers.

    with the hazard lights off, power from the wipers run through the hazard swithch to the flasher relay, then to the turn stalk and on to the turn lamp and to ground. I think that BMW feels that your most likely to use the hazards if its raining and therefore if the wiper's fuse is good, then so are the hazards.

    when you push the button and turn on the flashers the switch shuts off the power to the turn signals and turn on powers to the hazards. so in other words, it switches off power from fuse 15 and turns on power from 17.

    so you push the button and turn on the blinkers. power from fuse 17 is fed through the switch to the turn signal relay, through the relay and back to the switch, that power now alternating on and off by the relay is sent directly to the four bulbs and then ground bypassing the turn stalk.

    that's it. the hazard has nothing to do with anything else. not the radio or the horn. not the ignition or the back up lights. nothing but the wiper motor and really it's just sharing the fuse so unless the switch causes the fuse to blow it doesn't even effect the wipers. BUT, fuse 17 also feeds power to the interior/glove box lights so if fuse 17's circuit is bad it will kill the interior lights and the turn indicators but the problem is not cause by the hazard switch.

    Best explanation I have seen yet. Thank you, Tom Terrific!
    Tom
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  17. #17
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    Quote Originally Posted by dumbclub View Post
    I went out and removed mine (hazard switch) to verify. Turns out that the turn signals are the only thing that didn't work.
    you can jump the turn signal circuit with the hazard removed, just connect terminal 15 to 49 on the hazard plug, at least that how a 77 is done, all others probably connect the 1.5 vi/bk to the 1.5 gn/vi wires at the hazard plug.
    Tom D

    77 e21 - m42
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  18. #18
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    Quote Originally Posted by Tom D View Post
    but a mis-functioning hazard will not affect the wipers.
    I'm really not trying to start a fight, but a faulty hazard CAN stop the wipers, no fuse involved. I know from personal experience.

    Current: '10 E70 X5 35d | All my e21 parts are for sale!
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  19. #19
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    Quote Originally Posted by edennelson View Post
    I'm really not trying to start a fight, but a faulty hazard CAN stop the wipers, no fuse involved. I know from personal experience.
    '
    100% certain he's trolling. Yep, definitely trolling.

    Haha, jk edennelson. I've actually never heard this before, but I don't doubt its validity. And replacing that relay fixed the problem?

    Tom, that post is perfect. Not sure if it's in FAQ, but I am officially providing a motion to add it.
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  20. #20
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    Very nice write up on the power / fuse side of the hazard switch. Just keep in mind that it is not always about where the power is coming from. If the hazard switch breaks then the internal contacts can create connections that are never supposed to happen resulting in some strange side-effects. True, there is a limited number of possible outcomes but it is more complicated then simply where the power comes from.

    Over the years it has become more of a running joke of what we can blame the hazard switch for. Some are true, many are just for entertainment purposes.

    - Steve

  21. #21
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    I just want to buy a new replacement hazard switch. Whats the best place to get one?

  22. #22
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    eBay, Bav auto, az autohaus

  23. #23
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    so if my hazard doesnt work and everything else does then im just best off maybe just getting a new switch? i dont see it hurting as im sure its cheap enough. when i couldnt get my heater blower working i went to a pick n pull and got a few parts and then noticed the ac switch so i pulled it and replaced and bam worked like a charm. so thats what im hoping is all id need to do for the hazard. i went into the FAQ looking over it and really seems more of a pain to take apart and bend here n there just to get it working for a lil while longer when saving that energy and time just getting a new switch lol

  24. #24
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    New switches are very expensive. If you're on a budget you're much better off taking yours apart and fixing it. For a hazard that won't stay off, you just have to bend a small aluminum arm inside the switch and you're good to go. For the more complicated problems like Shauer referred to, you have to reposition the copper electrical contacts in the switch. It's a fairly simple job, you just have to be very careful when taking the switch apart. There's at least 3-4 guys on the forum that could show you scars from letting their knife or screwdriver slip when prying the switch apart.

    When you're done with the repair, the switch will be just as good as a brand new switch. Neither one is going to last forever.
    Last edited by bflan2001; 02-04-2013 at 01:43 PM.

  25. #25
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    ^ ditto.
    Well said and good advice.
    If you buy a new switch, you'll have the downtime while waiting for it to arrive, plus the small task of removing the old switch and plugging up the new one. It only takes a few minutes to repair the broken switch and as Brian (bflan2001) says, the new one won't last any longer than the repaired one.

    The best part of repairing the one you all ready have: The satisfaction of fixing something yourself and cheating "The Man".

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