240sx speedometer issues

[Jason062100]

Hello. I own an RB25DET swapped 1989 240sx and I've been having trouble with the speedometer. Whenever I'm driving, it seems to work, but it only works up to roughly 15 mph. The lights such as seat belts, fuel lights, door lights, etc. work correctly. The tachometer works fine as well. Any guidance will be greatly appreciated.

Thanks, Jason.

[GTSBoy]

What gearbox?

[Jason062100]

The stock r33 transmission.

[GTSBoy]

Do you understand how the speed sensor in that gearbox works? And how the speedo receives that and handles it and passes a different version of it to the ECU?

[Jason062100]

No not really.

[GTSBoy]

OK, so do some searching on here for the many words I have typed on the subject. Particularly you are looking for mentions of square wave and saw tooth and 0-1v and 0-5v and speedo and sender and so on.

What I have written is largely true for R32s and R33s. I do not know anything about the S chassis speedos. I am under the impression that they used electronic senders and so they should work similarly to the R33 type stuff. But they may not. You should use what I have written on SAU as a primer to help get you started understanding how these things can work, and should use it is guidance for what to look for in how the S chassis stuff works.

Edited September 10, 2019 by GTSBoy

[robbo_rb180]

You require a speed signal converter as the signals are different. Dakota digital do a converter or if you are keen to be covered in gearbox oil, swap in the original sender unit cog/drive onto the Rb25 sender as has been known to work on other Nissan gearboxes. 

http://www.nissansilvia.com/forums/topic/381889-rb-box-in-s13-how-to-get-speedo-to-work/

 

https://sxoc.com/vbb/archive/index.php/t-460010.html

Edited September 10, 2019 by robbo_rb180
Links added