97 Cars -- Tach signal from coil to Tach
Anyone have a schematic for this??? Reason I ask is because I have a 93 (the one that runs) with a 97 cluster in the car. Also had an MSD Digital 6+, and the tach worked fine. The Tach filter was still in the wiring harness. Recently, the MSD Died on me, so I trashed it and went back to the stock ignition. Knowing this, I removed the tach filter on the 93's harness to let the tach in the 97 get a signal.
However, it's not getting a clean signal at all. The tach is simply all over the place. It wouldn't move at all with the filter in the harness, so it's a step the right way, but what I need to find out is what kind of signal the tach is expecting to see so I can try to figure the right combination of resistors to wire into the signal like for the tach. From what I remember, in the 93's the tach gets it's signal directly from the coil, through the in-line filter. Aparrently in 94, this was changed to the coil sending a signal to the PCM which then sent a signal to the dash tach, with no in-line filter. I'm horrible with electrics, so don't laugh when I ask this: Would it simply be possible to measure the signal coming from the respective years locations (the coil output signal on the 93 and the PCM output signal on the 94+) and use resistors on my 93 to mimick the PCM output signal of the later cars?? If this is possible, would someone be willing to take a reading and get back to me?? Thanks for any help. |
Re: 97 Cars -- Tach signal from coil to Tach
subbing, b/c off my stock ignition I am not able to get any tach signal no matter where I try to get the signal....coil/PCM/etc.
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Re: 97 Cars -- Tach signal from coil to Tach
The coil doesn't send a signal to the PCM. The PCM reads the RPM off the Opti low res pulse signal, then sends a signal to the tach from pin A13. The connection from pin B5 to the ICM tells the system when to fire.
The signal is not a matter of "resistance"... its counting pulses. You would have to know how may pulses the PCM sends to the tach. |
Re: 97 Cars -- Tach signal from coil to Tach
Hmmm......that poses a problem then since I don't know how I'd replicate that signal on the 93. Maybe I just need to ante up and get another aftermarket ignition box.
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Re: 97 Cars -- Tach signal from coil to Tach
Originally Posted by Fastbird93
(Post 4169083)
Hmmm......that poses a problem then since I don't know how I'd replicate that signal on the 93. Maybe I just need to ante up and get another aftermarket ignition box.
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