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Turn Signal Wiring How-to

Discussion in 'The Hokey Ass Message Board' started by Crazy Steve, Mar 13, 2014.

  1. ... or almost everything you need to know to install/connect turn signals.

    You see these asked about all the time; 'how do I connect my turns on my '58 Whazzit?' and the general answer is usually 'look up the diagram on the net and go from there'. If you're somewhat wiring savvy, that may be enough but doesn't do much for the guy that doesn't own a Whazzit. So what if you have a oddball column/switch and can't find an exact diagram, or the switch is a service replacement with different colors (don't scoff, I've seen this), the number of wires in the car don't match the column, faded colors or you're colorblind? Or just 'electrically challenged' and intimidated by all the wires? Let's try to clear the mystery....

    When I said 'almost all', I'm not going to get into the really oddball stuff or European vehicles, I'm talking about units that are designed to use the rear brakes lights as the rear turns also and use a 'standard' two or three wire flasher. Most aftermarket turn signal units for early cars and pretty much all US cars originally equipped with signals are designed this way, but there are variations in wiring as the switches get newer and features were added. So lets talk about basic function.

    All these switches work basically the same, and there's a consistent logic in how the switching is done. You will find different numbers of wires though depending on switch features or design, so that's a good place to start; what wires you may find. First I'm going to number each wire and identify it's function (not all switches will have all wires), then I'll go through how to identify each wire using a continuity meter. If you have a late-model column with 'other' functions on it (cruise, wipers, etc), you need to separate those out. Note that these numbers are entirely arbitrary and unlikely to match however you identify your wires but are merely to show what connects to what when the switch is operated.

    The numbers:

    1. Brake light power. This wire will come from your brake light switch.
    2. Left rear brake/turn.
    3. right rear brake/turn.
    4. Left front turn.
    5. Right front turn.
    6. Turn signal power. This wire will come from the turn flasher ('L' terminal on a three wire flasher).
    7. Indicator light left.
    8. Indicator light right.
    9. Horn.
    10. Emergency flasher power. This wire will come from the emergency flasher.
    11. Indicator light power. This wire will come from the turn flasher ('P' terminal on a three wire flasher).
    12. Shift indicator light (some 'automatic' columns).

    Identifying the wires.

    Now let's get the meat of it. If you have fewer than six wires out of the switch, you have a turn-only switch and it isn't connected to the brake lights. Got six or more? Read the whole post and make sure you do this in the order shown or you can get hopelessly confused. Let's go...

    Six wires.

    This is your most basic switch. To identify the wires, start with the turns 'off'. You should read continuity between three wires only, and no continuity to/between the others. These are wires 1, 2, and 3 although we don't know which is which yet. Turn the switch to 'left'. One of these three will no longer read to the other two, this is wire 2. Turn the switch to 'right' and 2 now reads to one of the original three, but one won't read to the other two. The one that doesn't read is wire 3. That makes the remaining wire wire 1, or brake light power.

    I'll note here that no matter how many wires your switch has, this is the test to find the brake lights. You'll only find one group of three wires with the switch 'off'.

    To find the rest of the wires, turn the switch to 'left' again. You'll have continuity between 1 and 3 for brake, and between wire 2 and two of the other wires but not to 1 or 3. These are wires 4 and 6 although we don't know which is which yet. Note these, then turn the switch to 'right'. Now you'll have continuity between 1 and 2 for brake, and 3, 5, and 6 for turn. The one wire with no continuity to anything is wire 4, wire 6 is common to both left and right and is turn signal power, and all the wires are identified.

    This is the basic 'identifying test' that is done on any turn switch; any additional wires are simply added functions. In this case, if you want dash indicators for each side, connect those to wires 4 and 5. If you only want a single indicator for both sides, use a three wire flasher and connect the light power wire to the 'P' terminal on the flasher. I'll note here that a three wire flasher is only needed if you're using it to drive a dash indicator light or lights, otherwise a two wire flasher is all that's needed (sized for the lamp load of course).

    I'll add here that if you want/need a single dash indicator light but have an aftermarket fuse panel that won't accept a three wire flasher or don't want to add the flasher/wiring, there's a couple of ways to 'cheat' this so it works. If you use a standard 4W incandescent lamp for the indicator, then connect the wires going to the front turns to each side of the lamp (left one side, right the other) without a ground wire. The indicator light will get it's ground through the 'unused' front lamp, but the voltage drop through the small lamp is great enough that the front lamp won't light up or will glow very dimly. This won't work with a LED. As an alternative or if a LED is wanted, you can run a ground to the lamp then install a diode in each wire from the front turns before connecting both to the other side of lamp to prevent feedback into the side not 'on'.

    Got more than six wires?

    Seven wires.

    If you have a seventh wire and have an aftermarket switch with a built-in indicator light, this will connect to the 'P' terminal on a three wire flasher (wire 11). If you have a OEM type switch, this will likely be the horn wire (wire 9). If the horn goes through the switch, you should have a 'brush' that wipes on the steering wheel. This wire should not read to any other wire no matter what position the turn switch is in and if the steering wheel is installed with a working horn ring, should read to ground (the column) when the horn is pressed.

    More than Seven?

    At this point you're adding features. If you have emergency flashers it will be obvious. You may have separate wires coming off the switch for dash indicators, possibly even separate power for them. To find these, check like this, making sure you check each wire to all others:

    If you have two separate dash indicator wires, one of them will likely read continuity to wires 2, 4, 6 when the switch is on left, the other will read to 3, 5, 6 on right. These may read to their respective 'front side' wires of 4 and 5 all the time. If the wire size for 4/5 and 7/8 are the same, either one can be used for the front turn light. If you find a smaller gauge on one, use that for the indicator. If you still have an 'extra' wire and these don't read to the 'side' wires, they may have a separate power feed from the flasher 'P' terminal. Check to see if you have continuity between 7/11 (when 'on' left) and 8/11 (right) and no continuity to any other wires. Separate indicator power is rare on a OEM column, and won't be found if the switch has emergency flashers built in. This will require a three wire flasher if you want to retain this circuit, otherwise you can connect wire 11 to wire 6 and eliminate the need for a three wire flasher.

    If you have emergency flashers, when the switch is 'on' you'll have continuity between 2, 3, 4, 5, and 7, 8 (if present) as well as to one more wire, and this wire will be the power wire from the emergency flasher, wire 10. With the flasher 'off', this wire should not read to any other. Make sure this switch is 'off' while doing any prior checks.

    You might have a ground wire, but that should read to the metal column parts only, not to any other wires.

    If the column was out of a automatic-equipped vehicle, you may have an indicator light for gear position. This wire will connect to the dash lights.

    If the checks are done in order, this will identify the wiring on any switch. Do keep in mind though that switches do fail, so if you're using a used column and have issues, it may be the switch. Particularly look at columns that came out of vehicles that have done towing duty or may have had a camper installed; the extra load does shorten switch life.

    I'll add that if you're using a three wire flasher, the terminals are marked and must be connected correctly; 'X' is 12V power in, 'L' is load and goes to the turn switch, and 'P' is for indicator lights only.

    I'll note that this is 'generic' information, and while likely accurate for 99% of the US-built column switches out there, how the switches are connected to the OEM lights in the car may vary. Things like 'special' flashers, additional indicator lights on fenders or scoops, side roadway lighting when turning, sequential rear lights can have widely varying methods of factory wiring so you'll probably have to do additional research for the specific car with those features.

    Questions, comments welcome!
    Last edited: Jun 18, 2014
  2. missysdad1
    Joined: Dec 9, 2008
    Posts: 2,942


    Saved to "Favorites" for future reference. I've got two cars with mysterious turn signal wiring to sort out. This is a great reference on how to do it. Thanks very much in advance!
    VANDENPLAS and studebaker46 like this.
  3. d2_willys
    Joined: Sep 8, 2007
    Posts: 4,101

    from Kansas

    You may want to add to the thread about 53-60 Oldsmobiles and such that use the opposite front turn signal filament to ground the dash turn indicator.

    I have a 59 Olds that has this issue, that when you put a 3 terminal flasher (550), the P terminal is energized opposite the L terminal, thereby allowing both dash indicators to flash in unison. In this case you will need to build a flasher adapter or find the OEM flasher, which is getting rare. This adapter or OEM flasher allows the P and L terminals to energize at the same time, allowing the dash indicators to work properly.
  4. The OEMs did some strange things for whatever reasons, but some rewiring of the indicators will eliminate the need for any 'special' flasher. If you have a single dash indicator, look at the 'cheat' methods I mentioned. If they're separate (left, right), then feeding each from the respective side front lamp and grounding the other side of the lamp will fix it and a standard two-wire flasher will work.

    Even an aftermarket switch with an built-in indicator light that shows using a three wire flasher could be 'converted' to a two-wire flasher if you used diodes in the wires from the front lights when connecting both to the single input wire.

    If you're trying to retain originality, then you're stuck doing whatever it takes. This post is intended to give 'generic' information to give a working system but may require some mods to existing vehicle wiring.
    VANDENPLAS likes this.

  5. d2_willys
    Joined: Sep 8, 2007
    Posts: 4,101

    from Kansas

    Adapter works really well, and takes less than 30 seconds to install with 550 flasher. Not into cutting and splicing wires as it won't match OEM wiring diagrams.
  6. Atwater Mike
    Joined: May 31, 2002
    Posts: 10,226

    Atwater Mike

    Great post, Steve...I've had to deduce numerous switches customers would carry into the shop, but wouldn't have thought how to explain the operation to multitudes...

    Well done, concise and thorough. (I've copied the text to my favorites also...A good tool!)

  7. The37Kid
    Joined: Apr 30, 2004
    Posts: 27,256


    Thanks for posting the info Steve, I'll never understand it, or anything electrical, but recognize you sure spent a lot of time posting all this stuff. Bob
    Animal likes this.
  8. gow589gow
    Joined: Jan 5, 2012
    Posts: 47

    from Indiana

    Lot of older cars do not have flashers or automatic turn signals. "The Clever Turn Signal" is a controller which cancels the turn with inertia. When you make a turn and your glasses slide across the dash it picks up on this force and cancels the turn. It has input for turn signal, flashers and brakes lights. It has it's own internal audio feedback.

    It requires nothing on the steering column and uses a 2 position momentary switch. It can use a standard turn signal switch if the catch is removes so it returns to center (momentary on). It's an easy alternative to working with turn signals and flashers on an old car or custom car.

    It has a power wire, ground wire.

    Switch wires (Turn signal, flasher, brake input, and light input if you are using the front lights as markers)

    It has 6 wires for lights (2 for dash indicators).

    Last edited: Mar 14, 2014
  9. 270dodge
    Joined: Feb 11, 2012
    Posts: 742

    from Ohio

    Way good on you Crazy Steve. I'm installing an aftermarket column in a 63 Chevy C10. This is timely for me! Thanks.
    osut362 likes this.
  10. aircoup
    Joined: Aug 13, 2009
    Posts: 898


    glad i came across this im wiring my 56 turn signals now to a mid 80,s gm tilt column,i was just going to go to the wrecking yard and clip the wires from the upper part of the turn harness that plugs into the column part and add my existing harness wires after identifying all of them of course , does it sound like this would work ?:confused:
  11. aircoup
    Joined: Aug 13, 2009
    Posts: 898


    ok after reading your instructions ill still have to identify em this way, thanks
  12. aircoup
    Joined: Aug 13, 2009
    Posts: 898


    i noticed yesterday when i was installing a new turn signal assy that my flasher /plug for the flasher only has 2 wires no ground , ?should i add a ground wire ?
  13. aircoup
    Joined: Aug 13, 2009
    Posts: 898


    well that sounds stupid , i know ok but the two wire flasher is confusing ,
  14. flynbrian48
    Joined: Mar 10, 2008
    Posts: 6,507


    GREAT info! I somehow sorted out the (dealer installed) turn signal wiring on my '48 Pontiac convert when I rewired it with the LT1 engine, but how I did it is now lost in the dim recess' of my memory. This T'bird column has it's NSS in place, and that I can easily sort out because it's visible, and simple to sort out, but the turn signal switch wiring was causing me to scratch my head. Many thanks to you guys who responded to bail me out of this. Once again, the HAMB rocks!
  15. Kan Kustom
    Joined: Jul 20, 2009
    Posts: 2,618

    Kan Kustom

    Marking for future reference.
  16. jaw22w
    Joined: Mar 2, 2013
    Posts: 1,051

    from Indiana

    Not to side track this thread, but it is related. I need to add a very audible "turn signal on" warning for various reasons. Is there any way to do this?
  17. I'd use a 3-wire flasher and drive the beeper off the 'indicator' terminal on the flasher. Use a solid-state beeper to keep the current draw down. Second choice, connect the beeper to the input wire from the flasher to the turn switch but you'll probably need one of those 'flash any load' electronic flashers to make it work right.
    Hnstray likes this.
  18. jaw22w
    Joined: Mar 2, 2013
    Posts: 1,051

    from Indiana

    I knew it couldn't be that easy! This system has (2) 2 prong flashers. One for flashers and one for turns.
    Thanks for the input!
  19. goldmountain
    Joined: Jun 12, 2016
    Posts: 2,087


    I would place the buzzer in parallel around the 2 wire flasher.

    Sent from my SM-T350 using The H.A.M.B. mobile app
  20. Boden
    Joined: Oct 10, 2018
    Posts: 719


    wow. Thanks allot crazy Steve. That really helped out!

    Sent from my iPhone using The H.A.M.B. mobile app
  21. lake_harley
    Joined: Jun 4, 2017
    Posts: 1,059


    Crazy Steve.... I don't think you're crazy at all! Crazy helpful though for sure!

    I bought an unknown steering column and nice steering wheel at a swap meet last year and have been working on getting it in my Model A. I shortened the column and shaft, and the steering shaft is all worked out down to the steering box. The only thing that remained was identifying the turn signal switch assembly, for which I got a lot of help on in another thread I started. But, I still had to identify the wiring to get it all ready to wire, and your tutorial broke down the process to a very understandable and logical procedure. I got "proper continuity" through all of the steps to identify what wire goes where with the exception of the front left turn. I've narrowed it down that the problem almost has to be a bad reed switch down in the switch itself and electrical contact cleaner didn't work it's magic on that one, although I got good contact on everything else using the cleaner. I have a new switch assembly ordered from my local NAPA store and they'll have it in a couple hours. Pricy part? Yeah, a bit pricy, but I was really happy I could buy it locally and best of all, get it today!

    Thanks for your help! Good information lives forever here on the HAMB.

    brEad likes this.
  22. reefer
    Joined: Oct 17, 2001
    Posts: 743


    Great info and well written... I just fitted a SignalStat800 and traced out he wiring one at a time . Took a bit of thinking but worked a treat. Just need a couple of diodes to hook up an audible warning bleeper instead of a light as it’s a roadster and pretty noisy and easy to forget to cancel the indicator switch.
    Thor1 likes this.
  23. Sporty45
    Joined: Jun 1, 2015
    Posts: 834

    from NH Boonies

    Great info, thanks :cool:

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