guage swap question...89 guage cluster to 82 blazer????

[k5-newbie]

swapped TBI 350 and complete wiring harness, inside and out, runs fine...but there is a box on the back of the guage cluster that has 3 wires and has a circle with the letters "AC" in the middle of it. It comes off right next to where the speedometer cable plugs in. I dont' remember what wires I unplugged from it when I removed it /forums/images/graemlins/1zhelp.gif.
everything seems to work without this being plugged in, can someone tell me what this little box does??

Thanks in adavance,

Ben

 

[dyeager535]

It's the vehicle speed sensor, and it is used by the ECM to figure out a few things based on vehicle speed.

The wiring should be pretty easy to find. It also feeds the cruise control box, so you should have a couple of plugs that fit it.

 

[k5-newbie]

thanks...the only prob with that is that Im running a turbo 350 and of course the speed sensor is the only code im throwing now. Do I need a module or is there some way to "trick" the computer in thinking the 700R4 is still in it?

 

[dyeager535]

I don't believe (not positive, someone else with that vintage can comment) the 700 has any effect on VSS.

You don't want to trick the ECM with VSS, one of the results of not having VSS is stalling after a quick deceleration. Not always, but the VSS is used to "calibrate" the idle air control.

Anyways, the VSS takes its reading off the speedo cable in both 1982 and 1989, so there should be no reason you can't run it.

The box you described before is the VSS Buffer, and it only needs a ground and 12V ignition feed for wiring, plus the one wire to the ECM, pin A10 I'm sure.