Moekluse Posted June 2, 2023 Report Share Posted June 2, 2023 **First of all please move this if it is in the wrong location, this is my first post and one of the only places to put this as a new member** I am installing a Haltech elite 750 on my fathers 1987 Conquest TSI. The car is is nearly complete and is getting dyno tuned next week. I am finishing up some small odd ends and the last part is getting the tachometer to function properly. The engine is entirely stock including turbo etc. the original harness is in the car which I mated along with the new haltech ecu to provide instrumentation but I cannot locate the tach input wire. I can run a digital output from the haltech to the tach but I have looked at every forum I could find and was un able to locate. My service manual states it’s the w/b wire from the negative side of the of the coil. My issue is that my father removed the coil and most of the original engine controls and I’m left with a few dozen pigtails and wires to terminate. I believe the black and white wire was a switched 12v which I used for the ecu. I am not seeing any additional wires. Any help would be greatly appreciated! Link to comment Share on other sites More sharing options...
psu_Crash Posted June 3, 2023 Report Share Posted June 3, 2023 (edited) There should be a tach output from the Haltech. You can use that to drive the stock tach. It may require a little modification though since the stock tach was designed to read the inductive pulses from your coil firing. I connected the Tach out signal from my megasquirt to an opto-isolator then used that signal through a small inductor to give the pulses needed. Works like a charm. Although I have been told since then that the 12V square wave straight from the ECU may work. One of these days I'll give that a shot. You should be able to find that W/B wire at a plug on the back of the cluster. I thought it was a solid white wire on the negative side of the coil. Been a few years since I looked at that, so don't quote me. I can look it up and give you a hand if you need more information. Shoot me a PM if you like and I'll give you my number By the way I like that coil pack setup! Edited June 3, 2023 by psu_Crash Link to comment Share on other sites More sharing options...
tux Posted June 3, 2023 Report Share Posted June 3, 2023 I needed a pull up resistor for tach output on my AEM ECU. It's possible you may need to do the same Link to comment Share on other sites More sharing options...
tux Posted June 7, 2023 Report Share Posted June 7, 2023 i just saw that coil pack setup as I view from a computer, that is pretty slick. Link to comment Share on other sites More sharing options...
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