I am trying to find a source for a voltage output that is a function of speed. I would like to wire up a speed sensitive volume control for the stereo in the truck. In order to do this i need a voltage source that will increase as speed increases. My first thought i that most likely their should be some variable volatge output running the speedometer. If anyone know for sure or knows either what that voltage is or of another voltage source that is dependant on speed i would very much appreciate it.
Thanks,
Dan

 

It appears wiring diagrams for '04 can still be had on DC Bodybuilder site .

That's where I'd start.

HTH

Tony

 

The vehicle gets it's speed reading from a hall effect sensor mounted on the rear dif housing, so that wouldn't be the varying voltage you are looking for.

 

Very interesting mod. I completely understand the need. Plz let us know how it works out.

 

Is that anything like what they do on motorcycles?

 

mount a windmill to your hood

 

Hall effect?? Are you sure???????

I believe it is a PM generator that does deliver a variable A/C voltage.

 

I could be mistaken, but that's sure what it looks like?

 

windmill it is...
Thanks for all the replies. Ill check the above link and see if I can find anything for a voltage source there.
Ill post an update if i find anything

 

I have a '95 Z71 that has the variable volumn control. I have no idea how it works, but GM it might be a good place to look for info.

 

I think it's a super-neat idea, and let us know if you figure something out.

The Impala I drive at work has speed sensitive volume that can be set to off, high, or low. I'd guess the powertrain module gives the stereo some kind of signal?

 

From what I recall a speedometer works on the frequency that it is receiving. This is usually picked up from a hall effect pickup either in the transmission or somewhere on the driveline. This is really only varying the frequency and not the voltage to the speedometer. I don't know if you could use a type of pitot tube for an airplane or not. These usually have a plunger in them that moves forward or backwards depending on the amount of air pressure (speed) in front of the plunger. This would be a variable source, but I don't know if it would work for your particular application.

 

well pin 27 on the c2 connector is the vehicle speed sensor, and i have a couple of other possibilities as well. If i can fid my multi meter ill go for a drive and see what i can find.
thanks for all the replies so far as well.