Hi there,
I have a 1986 SE with a F328 rebody kit, and a Ferr@ri style interior, and I have been trying to get the speedometer to work. The instructions that came with the kit were incomplete about which wire to use, so I did a search here, and found an article about using a VSS buffer chip from a GM car (can't find the thread anymore - sorry). The thread described the problem, that the signal coming from the trannyis analog, and needs to be processed into a digital signal, 4,000 pulses per mile. So I got a VSS buffer, and I am trying to install the correct wires to it. this is what I tried so far, but it doesn't work.

from Fiero connector pin | to VSS buffer pin
S (VSS high) | 1
T (VSS low) | 2
N (to ECM) | 4

Does anyone know the correct wires to run to the VSS buffer?

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I guess I'd rather be a smarta$$ than a dumba$$

Which speedo are you using? Brand, model, etc. Maybe someone has done this swap already.

Thanks for responing, Hudini, the speedo is a VDO Visions programmable speedo. I currently have it programmed for 400 pulses per minute, which I was told is the correct setting for the Fiero. I'm not sure about which wires go to which pins on the VSS buffer. Anyone ever use this type? It is a Delco, #213225. I have a pic of the buffer and a schematic, how do I add them to this reply?

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I guess I'd rather be a smarta$$ than a dumba$$

Hey ktthecarguy,
Saw your car in your other post. Looks very nice (but a bit too high )

The Vss buffer puts out 4000 pulses per mile. As for posting images, at the bottom of the page there is an icon for the PFF image poster. Click that and follow the instructions.

Bob

I just read these instructions: http://www.egauges.com/pdf/vdo/0-515-012-051.pdf which state it is a programmable speedo so you do not need any buffer. You just set the speedo to 4000 pulses per mile and off you go.

"If you know the exact calibration value for the vehicle and type of sensor you are using (pulse-per-mile or pulse-perkilometer), you may use that value to manually calibrate the speedometer."

So, what to do? The wiring diagrams I have looked at show the VSS with a 2 wire output, VSS high and VSS low. This is like the inductive pickup 2 wire output that VDO describes? Just hook the wires up as per the inductive pickup instructions. Then take it for a test using the VDO instructions to check pulses per mile.

"VDO Programmable Speedometers can be used with inductive, hall-effect, reed and on manual transmissions, with OEM sensors."

[This message has been edited by Hudini (edited 06-09-2007).]

Where did you get the GM VSS buffer? I'm looking for an inexpensive source of those.

Hi Hudini,
Thanks for the info. I couldn't figure out from the instructions from VDO if it allowed the analog signal from the tranny, so I was trying to setup a digital signal. Can you tell me which wires in the Fiero console are the VSS High and VSS low? I thought it was the "S" wire for VSS high, and "T" for VSS low, but the colors didn't match what I was told.

Also, it seems like if I can get the speedo to work this way, I still will not have a digital 4,000 PPM signal going to the ECM. (I still get code 24 - no speed sensor).

JScott, try www.buy-oem-parts.com for the buffer, part #25071437. You have to register with them, but it doesn't cost anything. Price was higher than others at $78.00 but it was the only one that could obtain a buffer.
Is this what you mean?

Here's a pic of the speedo buffer from my 85SE; I removed it from the factory instrument pod where it was mounted near the factory speedo :



I'm using an ISSPRO programmable speedo and THE ONLY way it will work is by tapping off the small pins as shown. I don't remember if I had it programmed for 4000 or 8000 - 4000 I think. I have checked it using GPS and traffic radar signs and it is right on the money. Hope this helps

[This message has been edited by PaulJK (edited 06-12-2007).]