Wod 0 Posted May 6, 2014 Hi all, was looking for a bit of advice. I have taken on a 205 with conversion and just tidying bits up. Iv noticed the rev counter works but only at half the actual rpm of the engine? Does this mean the feed for the clocks is coming from a coil or something? Should it come from an ecu pin to the clocks? Cheers Share this post Link to post Share on other sites
Wod 0 Posted May 6, 2014 Could I connect a feed of the two coils via a diode and then into the clocks? Would that work? Share this post Link to post Share on other sites
Henry Yorke 269 3 Cars Posted May 11, 2014 You can modify the back of the tacho to get this to work as above (though I have not actually done this myself). It is the same mod that you do for a GTI6 conversion Share this post Link to post Share on other sites
Wod 0 Posted May 12, 2014 Iv come across this before but everyone says its when there tacho isnt working? mines just reading half :-( Cheers for reply Share this post Link to post Share on other sites
Anthony 1,000 Posted May 12, 2014 Sounds to me like the conversion was either wired up wrongly in the first place (ie it's wired only to one side of the coil) or that a tacho adapter was fitted and one of the diodes has failed so you're only seeing the output from one side of the coil. Unfortunately, you're going to have to have a poke around on the loom and see what's been done. 1 Share this post Link to post Share on other sites
Wod 0 Posted May 12, 2014 Wicked, il check this out then mate. If I want to take a feed from both coil negatives, can I take them off connected with diodes? And then straight into the clock? Cheers bud Share this post Link to post Share on other sites
welshpug 1,626 Posted May 12, 2014 Not quite, youll need a zener diode too, preferably a resistor to earth as well, simple enough to do and very cheap. 1 Share this post Link to post Share on other sites
Anthony 1,000 Posted May 12, 2014 You need to make something along these lines: Simple to make and works fine, although personally I prefer doing it "properly" and using the clean tacho out signal on the ECU and modifying the 205 tacho to work with it. Share this post Link to post Share on other sites
Wod 0 Posted May 12, 2014 You need to make something along these lines: Simple to make and works fine, although personally I prefer doing it "properly" and using the clean tacho out signal on the ECU and modifying the 205 tacho to work with it. Cheers man that looks dooable, the looms all sealed up so would be easier for me to do that for now. So I take it the above mod would work if the tacho gets its signal directly from the ecu? Would this just be a straight line from pin x straight into the tacho signal in or is there anything in between to account for? Thanks for the help guys Share this post Link to post Share on other sites
welshpug 1,626 Posted May 12, 2014 The signals would be the two coil triggers not the ecu tacho signal. Share this post Link to post Share on other sites
Wod 0 Posted May 12, 2014 So are you saying there actually is no ecu tacho signal? Im asking if I could wire it up to the ecu and just mod the clocks as another option Share this post Link to post Share on other sites
Anthony 1,000 Posted May 12, 2014 There's two ways of making the tacho work: You combine the two outputs from the wasted spark coil using the simple diode circuit above and wire this straight to the existing 205 tacho wire without modifying the tacho You wire the existing 205 tacho wire to the tacho out pin on the ECU and don't touch the coils, but you need to modify the 205 tacho PCB to remove/bypass part of the filter circuit so that it will work. Share this post Link to post Share on other sites
Wod 0 Posted May 12, 2014 There's two ways of making the tacho work: You combine the two outputs from the wasted spark coil using the simple diode circuit above and wire this straight to the existing 205 tacho wire without modifying the tacho You wire the existing 205 tacho wire to the tacho out pin on the ECU and don't touch the coils, but you need to modify the 205 tacho PCB to remove/bypass part of the filter circuit so that it will work. Thats it mate I was just double checking option 2 and making sure the line from the ecu is direct into the tacho Sounds easy enough! Thank you for the advise Share this post Link to post Share on other sites