Vehical Speed Sensor This is the back of an instrument panel from a 1985 IROC. I found this image on the Third Gen Tech Boards. The Third Gen website has been a hugh help in converting my 1977 camaro to throttle body fuel injection.
Vehical Speed Sensor This is an optical buffer and optic head. Often referred to as a Vehical Speed Sensor (VSS). This was the sensor GM used from 1982 to 1991. This sensor has an infrared emitter and sensor in the optic head. When the infrared light is reflected into the sensor the buffer creates a pulse to the engine control unit (ECU).
Vehical Speed Sensor You can see the part number here (25007318). This part has been discontinued by GM. The newer versions are green with a mounting tab and have a four pin connector. Although discontinued they can still be found new or used from the usual sources. They range in price from about 20 to 80 dollars depending where you find one. I got very lucky and found this one on eBay for $8.95.
Vehical Speed Sensor This is the optic head. Although it has a part number I suspect it's for GM only as I could not find any information on it.
Vehical Speed Sensor As you can see there is not a lot of components in the buffer box. I originally planned on building my own optical VSS but when I found this for $8.95 I bought it. Three reasons: 1) Already assembled, 2) TOO cheap to pass up, and 3) Cheaper than the parts to build my own. I couldn't find any information on the buffer box pinout so I opened it up. Very carefully drew a schematic and determined which pins were power, ground, and signal.
Vehical Speed Sensor Here you can see the mounting hole and the three connection points. The mounting hole is connected to the optic head signal line into the buffer. So if this hole is used to mount the buffer box make sure it is not a grounded metal connection or the buffer box will not generate pulses. Only use this hole for mounting to a plastic post.
Vehical Speed Sensor Here is the pinout for my TBI computer (1228746). Note my ECU originally used an AC generator with buffer that provided 2000 pulses per mile to the ECU. When completed this optical buffer will also create 2000 pulses per mile. On to the pinout: the pink with black stripe is power and is hot when in run, the black with white stripe is ECU ground, and the signal lead is brown pin A10 at the ECU connector.
Vehical Speed Sensor I have not removed my dash yet so I am using this generic picture of a cable driven speedometer. I found this image of a speedometer at Waltech Systems. This is where the idea began. I remember thinking this VSS is simple and effective. So the the hunt began to build a better mouse trap and thanks to eBay I found a great deal on the parts I needed.
Vehical Speed Sensor This is the rotating element from inside the speedo (image from Waltech Systems). Notice the two black and two white segments. The optic head with look through the hole in the speedo case and see these segments. Since white reflects infrared light and black does not the optic head and buffer will create 2 pulses for every revolution. Since speedometers are calibrated for 1000 revolutions per mile the VSS will generate the required 2000 pulses per mile for the ECU.
Vehical Speed Sensor I found some information at the Jags That Run website that helped this VSS project. Here's a link to more information on VSS from Jags That Run. Thank you Jags That Run.
Vehical Speed Sensor This is a pass through VSS from Autometer. It creates 16 pulses per revolution. If this sensor were used, a buffer would be needed to divide the output to get the desired output for the the ECU. In my case I would have build a circuit to divide 16000 pulses per mile by 8 for an output of 2000 pulses per mile that the ECU needs.
Vehical Speed Sensor Another example of a VSS this one is for a Ford or GM but that is all the information I have. Basically do the research and find what works for you and your ECU. Good luck with your projects.
