tachometer problems

[gotboost2jz]

95 240sx

My tachometer is completely wacked out. It does not read the proper RPM. I'll turn the car on and at idle it will bounce between 3k and 6k and continue to do so while I accelerate. Every once in a while it drops into range but eventaully resumes bouncing everywhere again. It's completely unpredictable. The speedometer also doesnt work but that's only because i have yet to change out the speed sensor to the US unit.

Is it bad wiring, or do I need a new dash cluster altogether?

[Rabboni]

I cant be sure, but it sounds like you have some crazy wiring gremlins to chase

[Dream240]

The tach gets it's signal from the ecu (terminal 3). So if you've got a tach problem, start tracing the wiring from there to the tach in the gauge cluster. If the wiring is good, then replace the tach unit.

The tach signal is not in any way connected to the speedo sensor. The only association is that they both use wires coming from the same harness connectors that plug into the cluster, but that's it.

[g6civcx]

What engine is in the car?

You can try connecting a service tach and check the output signal. If the service tach also jumps around then the problem is in the sender.

If the service tach works fine then the problem is in your wiring.

[gotboost2jz]

its an s13 sr
i'll just check the wiring when i return stateside. is it possible it could be a bad feed from a plug to the ECU?

[g6civcx]

its an s13 sr
i'll just check the wiring when i return stateside. is it possible it could be a bad feed from a plug to the ECU?

Either that or the ECU and/or cluster is bad.

[afiser]

i have the same problem, where is the rev sensor located? i wanted to check the wiring from the sensor to the ecu but im kinda clueless where to start.