Jun 25, 2006, 4:53 am · #1
Hey Guys,
How do i get my STD tacho to work on my ca18det?
I have a microtech computer.
It i have it wired up right
but it still doesn't work..
something about s12 dashes draw too much power?
STD Dash Tacho on CA18DET
Jun 25, 2006, 5:33 am · #2
Re tacho wiring, the sr or ca18det ECU won't run the s12 tacho. Only way its been done for an s12, (the people i know that have done it anyway), is to run 4 diodes, (worth 5 or 10 cents each from an electronics store) off the 4 wires that go from the ignitor to the coil packs, join them together and then run a wire from this to the tacho (guage), signal in wire. Diodes only send power in one direction, so current doesn't flow backwards and stuff up your ignitor etc.
But you must be careful and wire them facing the correct way. Here's a how to from someone whose done it successfully:
".....well used 4x IN4004 diodes connected to the coil side of the ignitor, about 3 inches from the plug is easy enough, then just joined the 4 diodes together on the tacho side and joined that wire straight to the tacho, the stripe on the diodes is towards the tacho (not sure if that is anode or cathode), and there you go....."
hmmm....gerrybg originally posted that btw...but when i copied and pasted the quote text it didnt post that...but yes, all credit can go to gerry...i just found it in the 18det how to write up which is only like half way done...we could use an complete wiring write up with pics and what not....one day:p.
Jun 25, 2006, 5:46 am · #3
Yep that's the way its done. My tacho factory tacho is wired up for the sr20det like this and works fine, (same for the ca18det).
I have a remapped factory ECU.
You can do it this way for either factory or after market ECUs. Most aftermarket ECU's should have a tacho signal to send to your tacho. If the ECU tacho signal out doesn't run your tacho, then just use the method above.
Jun 25, 2006, 10:34 am · #4
FKN CHAMPIONS! Cheers!
Jun 25, 2006, 11:25 am · #5
Here is the reason why. I found this little tid bit of info in SCC in a back issue from about 2 years ago. early Nissans used a strong signal from the motor which meant that the tach did not have to be as sensitive. However with the introduction of Coil-on-plug they switched to a ECU generated signal. this meant that the signal was not nearly as strong and thus was not strong enough for the old gauges to be powered by it. So with this in mind if you want a factory tach to work you will have to modify your instrument cluster to accomodate a newer S13 (SR or CA18DET only, no usdm ones), S14 (same as S13), S15, or other c-o-p vehicle. or do what they have said above, which will give you the stronger signal that you are looking for.
Jun 25, 2006, 6:41 pm · #6
exactly, well said.
Jul 12, 2007, 6:38 pm · #7
There is a light green and a dark green and a black in the plug going into the tacho back, You need to connect it to the light green
Jul 13, 2007, 1:54 am · #8
i traced mine (using a multi-meter) to the junction box and " T'd " it into there, so i can pull the dash in and out without having to re-join the wire each time.
Oct 22, 2008, 10:30 am · #9
Yeah no problem twat
Mar 13, 2009, 12:22 pm · #10
morgish @ Jun 25 2006, 05:53 AM
Hey Guys,
How do i get my STD tacho to work on my ca18det?
I have a microtech computer.
It i have it wired up right
but it still doesn't work..
something about s12 dashes draw too much power?
Im running std s12 tacho with ca18det Megasquirt/EDIS setup.
To get the tacho working I only had to jumper a input resistor on the the tacho.