MSgpio.com read only forums (Jan.15,2018)

So some history, Im converting a 700r4 to a 4l60e in my 84 corvette. All was going well, got it to the point where i ran through all the gears on the stands but i noticed a few things.

1. VSS is very jumpy, im going to change the wire to a sheilded one and raise the trigger voltage should solve that one

2. NonCAN Tach is not working, Now at first i reliazed i forgot to build the CCT, did that, still no tach, but it reads a steady 43 rpm with the random jump to a higher number and just stays there

3. My digital dash speedo is not working, so i did alot of reading and found that my old VSS goes straight to the cluster, then sends out the conditioned signal to the computer. For some reason the dash will not pick up the 12v squarewave from pwm1.

Now i cut the two wires for the old vss at the dash,
1. I have grounded one with the other hooked up to AMP31-no go,
2. Switched the leads-no go,
3. Cliped the pull up resistor and put 12v through a 1k resistor to the other side of the old vss imput-no go,

Then i start reading that the factory VSS input has to see a zero crossing event, how do i condition this CCT to work with my dash? Also just to make sure i took the old VSS put it on a drill and hooked it up to the two wires, works perfectaly so i have the right wires.

ysr,

For the VSS, see the tips here: http://www.msgpio.com/manuals/mshift/vss.html Many of the same tips apply for the tach input.

To force the the speedo signal to zero, you can try a weak 'pull-down'. To do this, put a 100k to 1M Ohm resistor from the VSS signal line to ground. However, you won't be able to get a zero-crossing, just to zero. That may not work with your speedo, I don't know. But it is relatively easy to try.

There are ways to convert a square wave to a proper sine wave, usually using an op-amp, see: http://alt.ife.tugraz.at/datashts/nsc/h7483.pdf You will have to keep in mind the frequency range of the VSS, which can range from as low as 1Hz to as much as 300kHz (see: http://forums.parallax.com/showthread.p ... post739083).

Or you could do what I did on my 84 Corvette and replace the dash (speedometer, oil pressure, coolant temperature, fuel gauge, etc.) with analog instruments - which aren't as prone to failure as the OEM gauges.

Lance.