Yet another wiring dilemma...for the love of god help

[Naloos13]

So i have an 89 hatch with a blacktop s13 sr. The motor came out of my friends 91 hatch and the tach worked just fine. He took it out and i put it in my car. I know my stock tach wont work with the sr so i bought a defi tach and i cant get any tach signal out of the yellow/red wire. I checked it with a multimeter and there is absolutely nothing there. So i decided to trace it through the firewall. Anyway, it led me to a dead end plug. So i was wondering if anyone could check there setup and see if this plug goes anywhere or if they even have it.

The plug is right before the plug that i cut to connect the sr and main power harness. It has a cap on the end but i dont know if it is supposed to be there or my friend did it.

excuse the ridiculously messy and dirty engine bay..and thanks for all the help
Modified by Naloos13 at 4:01 PM 9/17/2007

[highmilehatch]

I've never actually traced where the yellow/red tach wire goes to out in the engine bay, so I can't confirm if that plug is where it ends up. But if you used a multimeter and checked for continuity starting at the brown dash plug, then that should be it.

Here is what I would do to rule things out. Borrow a 91+ gauge cluster. Plug it in. Does the tach (on the cluster) work? Yes? It's probably a compatibility issue with your Defi tach. No? There is something else going on and you need to dig deeper.

[SpeedRacer1]

The tach wire gets its signal from somewhere in the inner engine harness, CAS area. If you are not getting a signal from the yellow/red wire then there is something wrong with the signal of that wire.

The wire in the picture is on all SR wiring harness' and is used for diagnostic purposes. It is not meant to be the signal for a gauge cluster tach.

1989-1990 tach's do not read the signal of SR's. But the Defi gauge should. Try to find out if the tach signal got cut somewhere on the inner engine harness.

[hpmachine]

Look for the red and yellow tach wire coming out of the ecu. I forget which pin it is, but you should be able to test for a signal there. I was having similar problems and I ended up running my tach directly off the cas wire.

[Naloos13]

I started testing for a signal at the ecu, and there was no signal, so i traced it through the harness to see if it was broken/see where it went. granted i skipped the joints because i saw the opposite end of the yellow/red which is seen in the pics. Im going to rip apart the harness again tonight

[hpmachine]

I gave up and assumed the tach driver in the ecu was dead. I also have those weird little gray connectors on my harness. I tested them and got nothing

[Naloos13]

I know its not the tach driver in the ecu, cuz i have 2, have tried both of mine as well as a friends. Also, that shouldnt matter because you splice the line before the ecu.

[hpmachine]

well if you find the problem make sure you post it up cuz it sounds like mine is similar

[Naloos13]

Still looking, im gonna finish going through the wires tomorrow. Im using the cas 180deg sensor to run my defi tach as of now. But as soon as i hit like 4500rpm it slows down. Basicaly its accurate until 4500, and then slows down, so when im at like 7500rpm it says like 5500. Anyone have this problem?