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    Haltech vs comm tacho

    I've been trying to get a factory tacho vs commodore cluster to work with the haltech Barra plug n play ecu. I originally wired it into dpo2 but changed it to dpo1 as others suggested. It is set as low active state, with 12v pull up voltage, 6 pulses per cycle and needle sweep 7000 rpm. It's wired into the small brown wire (neg coil) to the dash. The cluster works 100% as I tested it with my vr

    I tried the haltech 12v relay pull-up when it was with dpo2.
    http://www.haltech.com/wp-cont...y-W...ho-Output1.pdf

    I've also tried splicing into the signal and earthing with a 1k resistor.

    I have a feeling the signal is floating and needs to drop to 0v to get it to pulse. I'm not even getting a sweep to 7k.

    Any pointers?
    Do I try the relay thing again? But remove the coil part

    Sent from my HTC One M9 using Tapatalk
    Originally posted by 50RTD
    Dave, have you uploaded the data from the carby?

    #2
    Dumb question; do you have the relay connected the right way? Commodore relays have different pin configurations to the Haltech datasheet
    Originally posted by Marlin
    Chickens will slip under water in the cover of darkness like a seal team and FUCK YOU UP.

    Comment


      #3
      Very good point. But yes I've been caught out before. I carefully checked the numbers.

      Correct me if I'm wrong but isn't that what the 12v pull-up is doing, hence why I selected dpo1.

      Saying that, do I need 12v?

      Sent from my HTC One M9 using Tapatalk
      Originally posted by 50RTD
      Dave, have you uploaded the data from the carby?

      Comment


        #4
        I'm not an electronics expert, but is that actually a pull up? Or is the resistor protecting the Haltech from the induced voltage from the coil? I can't see how that resistor is pulling anything.

        Edit: I think something more like this, but check with someone who knows what they're talking about before frying your ecu
        Click image for larger version

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        Originally posted by Marlin
        Chickens will slip under water in the cover of darkness like a seal team and FUCK YOU UP.

        Comment


          #5
          Another idea. Lots of automotive relays have a diode or a resistor across the coil to snuff the induced voltage when they're switched off. If you used one of these relays as shown in the Haltech diagram (without removing the diode/resistor from it) then you wouldn't get the voltage spike to drive the tacho.


          Originally posted by Marlin
          Chickens will slip under water in the cover of darkness like a seal team and FUCK YOU UP.

          Comment


            #6
            that haltech drawing above says not to use the relay contacts at all, for some reason it wants the relay coil in series with the +12v and DPO with the 1k resistor on the DPO side. Im not smart enough to know why.

            Open the relay and pull out the contacts and resistor if installed. Wire it exactly as shown if its not already.

            Comment


              #7
              Originally posted by chartreusehj View Post
              that haltech drawing above says not to use the relay contacts at all, for some reason it wants the relay coil in series with the +12v and DPO with the 1k resistor on the DPO side. Im not smart enough to know why.

              Open the relay and pull out the contacts and resistor if installed. Wire it exactly as shown if its not already.
              I was thinking the same

              Sent from my HTC One M9 using Tapatalk
              Originally posted by 50RTD
              Dave, have you uploaded the data from the carby?

              Comment


                #8
                That's not a pull-up, a pull-up ties the signal line to the + supply. The resistor is inline, in a current-limiting capacity (increase in current draw will turn more power into heat at the resistor, dropping V+ as a result). Pull-up: resistor between signal and +; pull-down: resistor between signal and -.


                That haltech diagram is using the relay coil as an inductor, not using the switch features of the relay at all.

                Comment


                  #9
                  The relay coil generayes a field and colapses generating a voltage spike as the dpo cycles simulating an ignition coil.

                  Comment


                    #10
                    OK, I removed the points inside the relay. I checked the resistance and there was 70ohms. I hooked up the wires with 1k resistor and there was 1070 ohms across the relay/resistor.

                    Hooked it up and no luck.

                    I know I probably need an oscilloscope but checking the voltage out of the ecu is was 0.37v and with that modified relay 13+ volts.

                    Grrr, what am I doing wrong??


                    Do I need to bridge the 2 brown wires going to the tacho? Small brown for negative which I currently use and the big brown wire for positive

                    Sent from my HTC One M9 using Tapatalk
                    Originally posted by 50RTD
                    Dave, have you uploaded the data from the carby?

                    Comment


                      #11
                      Thinking out loud, does the 70 ohms mean there is a resistor or diode still in the relay?

                      Sent from my HTC One M9 using Tapatalk
                      Originally posted by 50RTD
                      Dave, have you uploaded the data from the carby?

                      Comment


                        #12
                        post up a photo of the circuit diagram on the side of the relay
                        Originally posted by Marlin
                        Chickens will slip under water in the cover of darkness like a seal team and FUCK YOU UP.

                        Comment


                          #13
                          .

                          Sent from my HTC One M9 using Tapatalk
                          Originally posted by 50RTD
                          Dave, have you uploaded the data from the carby?

                          Comment


                            #14
                            That looks like there is a resistor or diode across the coil to reduce spikes. I'd say you need a cheaper relay.

                            Comment


                              #15
                              Won't a diode be a triangle?

                              OK trip to repco

                              Sent from my HTC One M9 using Tapatalk
                              Originally posted by 50RTD
                              Dave, have you uploaded the data from the carby?

                              Comment

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