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    In desperate need of wiring clarity

    Hi everyone,

    Kind of a long post, but bear with me. I'm well outside my comfort zone. George Graves, Greg's///M, and Mo Brighta have all been very helpful thus far, but I'm obviously an idiot because I still need help and feel bad continuing to pester them.

    I've bought a pair of power Recaro seats I'm installing in my E30. E30s obviously never had power seats, so I need to run power to each seat. The power also has to be switched with the ignition because the seat has lighted buttons. Recaro suggests a 15A fuse per seat. The wiring coming out of the seat is 14 or 16 gauge, so 15A seems like plenty. This was my thought:

    My car has this auxiliary fuse box installed from the factory:


    The hot lead is rated at 26A, so my thought was to wire in a relay after this box. I found this image of wiring in a four-pin relay as a reference.

    The "hot" pin (30) would be attached to the red wire (constant hot), the switched pin (86) would be attached to the green wire (switched power), I'd ground the ground pin (85), and the current out pin (87) would then run to the seats. That way the seats only get power with the key on and the relay protects the buttons from getting overloaded.

    Each seat has a red and brown wire coming out of it. I'd ground each brown to the chassis and attach the red to the wire from the relay.

    Does that make sense? Wiring really isn't my strong suit so I'm struggling to conceptualize this. Some guidance would be very helpful.

    Thanks,

    Mike
    Last edited by ELVA164; 04-04-2017, 08:31 AM.
    Interested in vintage cars? Ever thought about racing one? Info, photos, videos, and more can be found at www.michaelsvintageracing.com!

    Elva Courier build thread here!

    #2
    I followed what you said, and it makes sense to me...

    ...for what that's worth!

    t
    now, sometimes I just mess with people. It's more entertaining that way. george graves

    Comment


      #3
      look up how to wire fog lights or driving lights with a relay and fuse. It's the exact same thing and you should be able to find a diagram pretty easily and quickly learn how to draw your own.

      being nitpicky but that drawing does not accurately represent the layout of a relays ground pins. This one does (sorry photobucket)

      but essentially you would take the brown seat wire to ground and the red seat wire to pin 87 of the relay. Put the fuse between the power source and the relay like in the diagram


      it's a Kenny Powers quote on wheels

      Comment


        #4
        Why don't you just use power off the ignition wires inside the car?

        Comment


          #5
          A great resource for all things electrical on just about any car is http://www.the12volt.com/

          It's really handy. If you can use a mulimeter and read a very simple schematic, it's for you.

          For example. You're looking to turn on a larger load with a smaller. For something like a seat heater that's perfect. Heres a diagram that will work - it's made for the "remote" wire from a head unit to turn on camp cooling fans, but it's the right idea. You just have to make sure you get a good relay that won't weld it's contacts together. That could cause a fire. So do this at your own risk: (I'm not sure how much current seat heaters take, but I'm sure it's approaching 15-30 amps at 12 volts)





          Another trick I shared with OP is that for safty, some people place two relays in series. That way if one fails (self welding contacts) the other is ok. But it's kinda of a hack. To really do it you need to monitor current, but then you're into a much more complex circuit.

          Just my 2 cents.
          Last edited by george graves; 04-06-2017, 12:43 AM.
          Originally posted by Matt-B
          hey does anyone know anyone who gets upset and makes electronics?

          Comment


            #6
            Thanks guys!

            Originally posted by Das Delfin View Post
            look up how to wire fog lights or driving lights with a relay and fuse. It's the exact same thing and you should be able to find a diagram pretty easily and quickly learn how to draw your own.

            being nitpicky but that drawing does not accurately represent the layout of a relays ground pins. This one does (sorry photobucket)

            but essentially you would take the brown seat wire to ground and the red seat wire to pin 87 of the relay. Put the fuse between the power source and the relay like in the diagram
            Alright, so if I have two seats I'm installing (driver and passenger), can I run both brown wires to the same ground pin and both red wires to pin 87? I'd have only one wire running to the relay itself, but I'd tee off it inside the car to go to both seats.

            Originally posted by kgiynmgs View Post
            Why don't you just use power off the ignition wires inside the car?
            I want to molest the car as little as possible; that's one of my mantras when doing modifications.

            Originally posted by george graves View Post
            A great resource for all things electrical on just about any car is http://www.the12volt.com/

            It's really handy. If you can use a mulimeter and read a very simple schematic, it's for you.

            For example. You're looking to turn on a larger load with a smaller. For something like a seat heater that's perfect. Heres a diagram that will work - it's made for the "remote" wire from a head unit to turn on camp cooling fans, but it's the right idea. You just have to make sure you get a good relay that won't weld it's contacts together. That could cause a fire. So do this at your own risk: (I'm not sure how much current seat heaters take, but I'm sure it's approaching 15-30 amps at 12 volts)





            Another trick I shared with OP is that for safty, some people place two relays in series. That way if one fails (self welding contacts) the other is ok. But it's kinda of a hack. To really do it you need to monitor current, but then you're into a much more complex circuit.

            Just my 2 cents.
            Looking forward to reading this tonight!

            It may be answered in there and if so ignore this, but I'll be using the factory harness for the seat heaters. This circuit is for the power seat back and the bitty air compressor for lumbar support. Basically, smaller load and very momentary. I'll obviously still be looking for a quality relay, but will this setup be safe otherwise?
            Interested in vintage cars? Ever thought about racing one? Info, photos, videos, and more can be found at www.michaelsvintageracing.com!

            Elva Courier build thread here!

            Comment


              #7
              Originally posted by ELVA164 View Post
              Thanks guys!


              Alright, so if I have two seats I'm installing (driver and passenger), can I run both brown wires to the same ground pin and both red wires to pin 87? I'd have only one wire running to the relay itself, but I'd tee off it inside the car to go to both seats.

              I would use a fuse on each seat before the tee if you do this

              Comment


                #8
                Originally posted by E30 manic View Post
                I would use a fuse on each seat before the tee if you do this
                Just in case something goes wrong with the wiring inside one of the seats? Is there a better alternative method to the one I described?




                So I've found a Hella 4-pin relay to use. I'd also like to get a socket. I assume brand is just as important on this end?
                Interested in vintage cars? Ever thought about racing one? Info, photos, videos, and more can be found at www.michaelsvintageracing.com!

                Elva Courier build thread here!

                Comment


                  #9
                  Wait, why are you even using a relay? The aux fuse box has two fuses, one is hot at all times, while the other is hot with ignition. If you use the second you don't need a relay. Test with a multimeter to verify but I believe the fuse with the green lead is switched.

                  The point of a relay, for example with fog lights, is so you aren't running an unnecessary amount of current through the switch in the dash. This keeps it safe while reducing voltage drop, crucial for light output. Running extra wire through a switch really does drop the volts like crazy and makes lights go dim quick.

                  Does your plan with these seats involve a switch on the dash to turn their power functions on or off? If not, then you don't need a relay. All you need is a wire from your aux fuse box to the red wire from the seat.

                  "Trying to protect the seat buttons" is pointless if there is only a red and a brown, ie there is only one source of power for the seat. The same red wire supplies power to the motors as well as the switches.

                  Furthermore, as it happens the stock e30 window switches are designed to run the entirety of the current needed to actuate the window through the switch. Which is another example of a 12v source powering an electric motor without a relay. Really there's no place to put a relay because you don't use a relay to protect a circuit (that's the job of a fuse), you use a relay to provide a remote switch.

                  Also,

                  Originally posted by ELVA164 View Post
                  Just in case something goes wrong with the wiring inside one of the seats? Is there a better alternative method to the one I described?
                  because, as you described in your OP,

                  Originally posted by ELVA164 View Post
                  Recaro suggests a 15A fuse per seat.
                  but to explain with reason, any time you can isolate a circuit, do it. Reduces possible damage to wiring and components and makes troubleshooting easier.

                  Really don't overthink this stuff. It helps to conceptualize it in your head and write down what you want it to do. Kinda like "if this happens, then we need to do this" Electronics are all about making stuff go from one place to another and working within a system of rules. This one being the seats are protected by their fuses and a relay has a different job altogether.

                  Alternatively, you can forgo the aux fuse box entirely and just pick a hot with ignition power source capable of supplying the necessary current and just put a fuse in line for each seat. But in this case there's still no application for a relay. Because there's no "master switch" for the seat. Does that make sense? You only use a relay when you want something switched by remote.

                  To clarify George's post, he was talking about seat heaters, which do have a switch in the dash, and you would want to use a relay make the circuit as efficient as possible. Because they have a dash switch.
                  Last edited by Das Delfin; 04-14-2017, 12:48 AM.


                  it's a Kenny Powers quote on wheels

                  Comment


                    #10
                    Thanks for all the info. I ran a relay because the switched power in the aux box is a pretty thin wire, too small to run to both seats. I ended up wiring it as described, the seats are powered at key on, and the motor and compressor work fine. Success! Now to figure out the heated seat wiring... Sheesh, always another hurdle with these darn seats.
                    Interested in vintage cars? Ever thought about racing one? Info, photos, videos, and more can be found at www.michaelsvintageracing.com!

                    Elva Courier build thread here!

                    Comment


                      #11
                      I don't think you understood what I was saying at all but whatever floats your boat


                      it's a Kenny Powers quote on wheels

                      Comment


                        #12
                        Originally posted by Das Delfin View Post
                        I don't think you understood what I was saying at all but whatever floats your boat
                        If I were to run both seats directly to the switched lead in the box, the potential current draw would be higher than what that green wire and its fuse are capable of. The constant-hot wire is a lower gauge, so I used the relay to effectively switch the heavier wire.
                        Interested in vintage cars? Ever thought about racing one? Info, photos, videos, and more can be found at www.michaelsvintageracing.com!

                        Elva Courier build thread here!

                        Comment


                          #13
                          So the wiring I'd laid out for the seats is working perfectly! I've also installed the harness for the seat heaters, just have to do some troubleshooting to get the operation correct. Here they are!







                          Need a couple small things to finish up the installation location-wise, but they're awesome.
                          Interested in vintage cars? Ever thought about racing one? Info, photos, videos, and more can be found at www.michaelsvintageracing.com!

                          Elva Courier build thread here!

                          Comment


                            #14
                            My stock "is" sports seats are cool and all - but they will never be as cool as recadros with switches.

                            Glad you got it all working.

                            BTW - back in the day those seats were about the most you could spend on seats. Top of the line.
                            Originally posted by Matt-B
                            hey does anyone know anyone who gets upset and makes electronics?

                            Comment


                              #15
                              Originally posted by george graves View Post
                              My stock "is" sports seats are cool and all - but they will never be as cool as recadros with switches.

                              Glad you got it all working.

                              BTW - back in the day those seats were about the most you could spend on seats. Top of the line.
                              Thanks for the compliment and the help! I'm going to take some more time and see if I can figure out a way to get the "low" and "high" sides of the heater switches working with the seats instead of just the "high."

                              You're correct about the cost: The first generation of these seats was available in E30s as a dealer-installed option.......






                              ..... For six thousand dollars.


                              Gulp.
                              Interested in vintage cars? Ever thought about racing one? Info, photos, videos, and more can be found at www.michaelsvintageracing.com!

                              Elva Courier build thread here!

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