tach and speedo update - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

240S15DETE6K · 12-13-2001, 08:39 PM

OK, so I've determined that the gauge cluster is receiving a variable voltage signal from the ECU to drive the tach and speedo.  The ECU generates this voltage porportional to the frequencies it receives from the speed sensor and the (?) for the tach.  The weird thing is that the FSM makes reference to this voltage being AC?  Does anyone have any idea what the frequency of this AC signal may be?  I know this is a long shot, but once I determine this, it'll be easy to make a circuit to drive the factory gauges, from any frequency, be it a ABS sensor, flywheel sensor etc.  I'll include these circuits in my "S15 drivetrain into S14 chassis kit" :-)

gfisch · 12-13-2001, 11:16 PM

Just run it to an osciliscope if you have access to one. It'd be real easy to see the freq. of the AC signal.
It makes sense its an AC signal, they do that to reduce the effects of interference. we did that on some industrial machinery i was wiring over the summer.
If you have questions, jast ask me. I'm a senior Electrical Engineer at RPI, so I could probably help you out.

Greg
[email protected]

240S15DETE6K · 12-14-2001, 09:45 PM

Cool, I'm a EE too.  The problem is that I don't have a functioning ECU now that the swap is done.  If I can locate a willing 240 in the area that's exactly what I'll do.  Thanks, I'll let you know what I find out.

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12-13-2001, 08:39 PM	#1
240S15DETE6K Leaky Injector Join Date: Oct 2001 Posts: 95 Trader Rating: (0) Feedback Score: 0 reviews	OK, so I've determined that the gauge cluster is receiving a variable voltage signal from the ECU to drive the tach and speedo.  The ECU generates this voltage porportional to the frequencies it receives from the speed sensor and the (?) for the tach.  The weird thing is that the FSM makes reference to this voltage being AC?  Does anyone have any idea what the frequency of this AC signal may be?  I know this is a long shot, but once I determine this, it'll be easy to make a circuit to drive the factory gauges, from any frequency, be it a ABS sensor, flywheel sensor etc.  I'll include these circuits in my "S15 drivetrain into S14 chassis kit" :-)

12-13-2001, 11:16 PM	#2
gfisch Zilvia Junkie Join Date: May 2001 Location: Warren,NJ / Baltimore,MD Age: 44 Posts: 576 Trader Rating: (0) Feedback Score: 0 reviews	Just run it to an osciliscope if you have access to one. It'd be real easy to see the freq. of the AC signal. It makes sense its an AC signal, they do that to reduce the effects of interference. we did that on some industrial machinery i was wiring over the summer. If you have questions, jast ask me. I'm a senior Electrical Engineer at RPI, so I could probably help you out. Greg [email protected]

12-14-2001, 09:45 PM	#3
240S15DETE6K Leaky Injector Join Date: Oct 2001 Posts: 95 Trader Rating: (0) Feedback Score: 0 reviews	Cool, I'm a EE too.  The problem is that I don't have a functioning ECU now that the swap is done.  If I can locate a willing 240 in the area that's exactly what I'll do.  Thanks, I'll let you know what I find out.