Posessed Tachometer

[afiser]

1995 240sx Base

Okay, first off. i have spent the last few months searching, using trial and error, doing anything i could possibly do to fix my tachometer. i have nothing to show for it.

I kinda have OCD when it comes to my gauges and with this one not working (the one i would use the most) it is really an upset.

But anyways, i have switched out clusters, checked the signal with a multimeter (this test seemed to have checked out, but this was a little while ago and im not 100% on the results i got), checked ECU codes, etc...

I guess my main question is where and how does the RPM signal get from the engine to the cluster? I know the cluster gets the yellow red stripe coming from the ECU, but from there im clueless.

i dont know what else to check but im determined to get this to work. so please, any help would be GREATLY appreciated.

[AS240]

my friend had that problem in his s13. turns out he has crap engine grounds. check all your engine grounds and you could even make a few more. its good to have a couple extra anyways

[slim_240]

i guess look up the pinout on the ecu. mines was doing the same thing and jumping around. i just kicked my ecu and it clicked back on. eventually i just fixed one of the pins.

[slider2828]

It could be ECU, but mine is an SR and it sends a pulse signal to the tach... its either the ecu or the gauge... BUT it goes to the white plug to the dash from the engine harness before the ecu.... I would check those wires.... Its a white plug to the right of the glove box...

[afiser]

thanks for the help

[5pecialist]

Any luck? My tach likes to do it's own thing.

[afiser]

nope not really shit, works more than usual lately but i didnt do anything for it to be that way.

still doesnt work 100% right.

[jasonb]

nope not really shit, works more than usual lately but i didnt do anything for it to be that way.

still doesnt work 100% right.

late to the party, but whats wrong with ur tach? i put a scope on tach signal coming out of my sr20 ecu while back and it was a 5v square wave. maybe your tach can't reliably read 0-5v square wave?

(i have a aim mxl strada and it can't read 5v tach signal so i had to use a pull-up resistor on it to get mine to work).

[afiser]

interesting, well i have tried 2 different tach's with the same results i dont think the tach is the problem. however i do think the ecu is not giving a good signal. either that or the signal between the tach and ecu or ecu to whereever it gets the rpm is borked. so much crap to go wrong and i have no idea how to check it lol.

[Slidin' Sam]

Check where the tach/ecu actually reads the rpm's. maybe the sending unit is bad. my friend had this issue on his r32 (had a grounding kit too) and his tach did whatever it wanted, it would work sometimes, then other times it would act like a clock and just go around in circles. He just hooked up a defi tach and called it a day...

[TFD]

I hooked up my datascan and it reads revs perfect where my tacho f*cks up. Now you know the ecu works and the problem is in the wires or gauge.

[Slidin' Sam]

Trace wires then or borrow a one from a friend and test. If the borrowed one works then its not wiring and you will know what you have to do.