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    12V+ to Relay block question

    Not sure if this belongs here or in the electrical subsection so bare with me if Ive gotten it wrong.

    Attempting to wire a Haltech Sprint 500; I say attempting because ive never done anything of this size scope before so its new ground for me. Bought and fitted a fuse and relay block in an attempt to make everything neater for the ECU related wiring additions. Fuse/relay block is non-bussed and has 5x relay blocks and 6x fuse blocks. I intend to run the following in the relay blocks:

    1x relay for starter
    1x relay for thermo fan
    2x relays for ECU power
    1x relay for fuel pump

    In the interests of neatness, instead of running an individual 12V feed wire from battery to pin 30 on each relay, can I run a single feed from Battery and what is the correct way of wiring it? Does it get daisy chained [12v battery to relay 1 to relay 2 to relay 3 etc direct to pin 30] or should I be running the 12V up to the fuse block and have a wire for each relay crimped to the 12V feed via the fuse block first [fuse on 12V+ pre relay].

    Also, this will sound ridiculously dumb, but should it be fused pre-relay or post relay?
    1978 Gemini Sedan - Powered by i change my mind every week
    1980 Gemini Sedan
    1992 Land Rover Discovery 200TDI

    #2
    daisy chain is ok, I would suggest you do it with a small power distribution block like this. https://www.jaycar.com.au/twin-m6-po...plate/p/SZ2094

    You could run 12v to one size and battery Neg to the other.


    as for the relay pin outs, this might help as a guide

    Relay 1 - Starter (no fuse)

    30 Battery 12V
    85 Ground
    86 - 12V from key starter position
    87 - 12V to starter solenoid

    Relay 2: Thermo Fan

    30 - Battery 12V
    85 - ECU DPO / PWM output
    86 - 12V from ECU relay 3 (pin 87A)
    87 - 12V to fan

    Relay 3 : ECU/Injectors - use a 5 post relay (not change-over)

    30 - Battery 12v
    85 - Ground
    86 - 12v IGN from key (make sure its a proper 12v ign source and does cut out while cranking
    87 - 12v to ECU and injectors
    87a - 12v to Pin 86 Relay 2, 4, 5

    Relay 4: - ECU (ignition)

    30 Battery 12v
    85 - Ground
    86 - 12v from Relay 3 (pin 87a)
    87 - 12v to ign coils

    relay 5 - Fuel pump

    30 Battery
    85 - ECU pump ouput
    86 - 12v from relay 3 (pin 87a)
    87 - 12v to pump +ve

    I would put a fuse between the battery supply and Pin 30 on relays 2-5

    Comment


      #3
      Mate you are an absolute fucking champion! Thanks heaps, just saved me a giant headache (i was in the process of working each relay out relay by relay....lol)
      Attached Files
      1978 Gemini Sedan - Powered by i change my mind every week
      1980 Gemini Sedan
      1992 Land Rover Discovery 200TDI

      Comment


        #4
        Another quicky - 12V from battery to fuse/pin 30; 16gauge enough to go from battery to distribution block? Quick google says its rated to 30amp if within 1.9' [fucking americans seriously]. Battery to fuse block is approx 400mm away so well within the length requirement
        1978 Gemini Sedan - Powered by i change my mind every week
        1980 Gemini Sedan
        1992 Land Rover Discovery 200TDI

        Comment


          #5
          id use bigger stuff. from the 'battery' +ve distribtution block thing to the terminal 30's use 3mm for ecu related and 4 for fan and fuel pumps.. or just overkill all that to 4mm..


          from the actual battery to the distribution jaycar block thing, use some beefy cable like 6mm..

          Comment


            #6
            Sorry for the thread hijack, but what's a decent brand of wire to use and where would be the best place to source it?

            Comment


              #7
              Originally posted by tim510 View Post
              id use bigger stuff. from the 'battery' +ve distribtution block thing to the terminal 30's use 3mm for ecu related and 4 for fan and fuel pumps.. or just overkill all that to 4mm..
              Roger that.

              What gauge from pin 87a to the 3 amigos [pin 86 on relays 2, 4 and 5]? Looking at the terminal and wondering how im going to fit 3 wires into it and get it to crimp properly lol

              from the actual battery to the distribution jaycar block thing, use some beefy cable like 6mm.. [/QUOTE]

              Originally posted by 080GMH View Post
              Sorry for the thread hijack, but what's a decent brand of wire to use and where would be the best place to source it?
              Hijack away bud, looking like im going to need wire too
              Last edited by F3ARED; 11-11-20, 04:32 PM.
              1978 Gemini Sedan - Powered by i change my mind every week
              1980 Gemini Sedan
              1992 Land Rover Discovery 200TDI

              Comment


                #8
                Originally posted by tim510 View Post
                ...
                Relay 3 : ECU/Injectors - use a 5 post relay (not change-over)

                30 - Battery 12v
                85 - Ground
                86 - 12v IGN from key (make sure its a proper 12v ign source and does cut out while cranking
                87 - 12v to ECU and injectors
                87a - 12v to Pin 86 Relay 2, 4, 5
                ...
                I think there is some confusion here. Shouldn't 87a be the second 87 terminal?

                Comment


                  #9
                  Originally posted by elfturbomax View Post
                  I think there is some confusion here. Shouldn't 87a be the second 87 terminal?
                  I don’t understand what you mean?

                  Comment


                    #10
                    3 amigos? There is fk all current draw , so little stuff/big stuff, what ever you can terminate nicely.

                    Comment


                      #11
                      For relay 3 you said don't use a changeover relay. But you have listed the terminals as 30, 85, 86, 87, 87a. The 87a signifies a changeover relay. A non-changeover relay has two 87 terminals.

                      Comment


                        #12
                        Ahhhhh, now understand. You knew what I meant anyway.

                        Comment


                          #13
                          So to confirm, the 5pin relay needs 2x 87 pins not an 87a?

                          Cant thank you enough. Youve made this so fucking easy
                          1978 Gemini Sedan - Powered by i change my mind every week
                          1980 Gemini Sedan
                          1992 Land Rover Discovery 200TDI

                          Comment


                            #14
                            yes that correct.

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                              #15
                              Is tycab wire any good? I wouldn"t mind some multicore that has a variety of colours as it would probably be more cost effective getting it that way.

                              You can get it in trailer wiring but is that up to the standard to use in an engine bay?

                              I have heard tefzel mentioned before but pretty sure that is mega $$$ and probably overkill unless you are looking at saving weight and probably not much point unless you use those expensive circular mill spec connectors.

                              Comment

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