I was recently swapping to an electric speedometer in my 89 and discovered a circuit on the gauge cluster reading "SPEED SENSOR".

In the swap I am doing this circuit is no longer connected to the speedometer. My concern is it appears that this is connected to the power steering controller, cruise control and auto belts.




I'm not concerned with the powersteering as I have depowered my rack, I can worry about cruise control later, but I am concerned about the effectiveness of my restraints for safety reasons.

So on the autobelt side of things the wiring doesnt give much of a clue to its function.



I have driven the car this summer with no speedometer cable connected this summer with no apparent consequence, but then I have not been in an accident.

Does anyone have a more indepth knowledge of how this particular circuit functions?

 

Also looking at the autobelt wiring diagram there doesn't seem to be anything fancy going on. It appears to mostly just control the positioning of the autobelt in either the unrestrained or restrained position. Also it appears to sense the position of the door locks.

Could this speed sensor just be for sending a warning light if the belt is not in the restrained position while the car is moving?

 

I believe you are absolutely correct. My vert obviously doesn't have mouse belts, but I know for a fact that same G/R wire is at the buckle latch. My CPU failed and went psyco (pretty common) and I didn't bother fixing it. That G/R wire is positive trigger so you can just disconnect it and problem solved. It's just there for the seatbelt light and buzzer to bitch at you.

I know it just ends at a block in the diagram but that wire connects to the transistor on the left of the black labeled "Warning Circuit".

 

Thanks for the vote of confidence.

Does anyone have a firm understanding of the speed sensor function with respect to the auto belts?

 

I'm going to move forward without this connection made. I may tear apart a restraint module and see if I can see what is going on for sure. If I do that, I will report back here to document this information.

 

no, but i'm pretty sure its just to let the thing know you're moving so it can turn on a light or something like that. the belts work with the doors being opened or closed, and so the speed must be something else, and there isn't much that could be.

in 89 the system won't have pre tensioners or anything fancy in it either