I have the factory radio with the extra 20 pin connector. It supports speed sensitive volume control, but it is not wired in on my vehicle. I believe that the needed signal comes in on pin 9 of the 20 pin connector, but I am not sure which signal to connect. Does anyone have a wiring diagram that calls out the Ford signal name for pin 9? Or does anyone have the pin connected and could tell me the colors of the wire?

Thanks,
Joe

 

Joe,

It is the vehicle speed input from the GEM to the radio. It is pin 14 off the GEM.

Regards


Jean Marc Chartier

 

In an attempt to try to NOT sound stupid, How did you determine that you have the speed sensitive volume control in your truck?

How can I (or anyone) check to see if they have it???? Thanks.

 

Thanks for the responses.
1. Unfortunately, I do not have a single "GEM." Instead, I have a door module, LCM, wiper, and chime modules. The only wire that I know for sure that has speed information is the VSS+ wire. It goes to the speedo, cruise, and engine computer. I guess it probably won't hurt to try it.

2. You can tell by turning the radio on, then hold down the on/off button. After a little while, "SPEED VOL 0" will appear in the display. 0 is off. You can adjust from 0 to 7 with the select buttons. However, it still doesn't work if the speed signal is not connected.

Joe

 

I'm kind of glad I don't have that. I like to have the radio cranked while I drive slow, and a more reasonable level when on the interstate. Kind of the opposite ,,,,98

 

Not knowing the year of your rig, I can only offer this:

According to my Ford CD, the 20 pin connector does use pin 9 for the VSS input. The wire should be Grey/Pink.

This was taken from a 2000 F150 diagram, but it should work for several other years as well.

 

Yep, my radio does have the speed volume control...I tried it and it works great...thanks for the help and input

 

Thanks B-man. That was exactly the information I was looking for. I'll probably try it this weekend, and will post the results.

Joe

 

Tried it, doesn't seem to be working.
Joe

 

Joe,

What year and model truck do you have?

JMC

 

Actually, I don't have a truck (at the moment anyway). I have two Mercury Grand Marquis, 1999 & 2000. The owner's manuals say the feature is supposed to work on both, but it doesn't. The radios have the speed vol setting, and I assume they are the same as the truck ones. I tried feeding a squarewave into pin 9 of the radio at different frequencies, but that had no effect either. At this point, I assume that I have the wrong pin on the radio, or that I need other connections, such as the SCP bus.
Joe

 

The radio uses the speed input circuit from the PCM. I traced the input back to the PCM. It goes from the PCM to the radio directly. It also goes to the Speed Control Servo and to the GEM. It is circuit # 679 on the trucks. Same color wire to all three units. Hope this helps.

JMC

 

If you can't get it to work, you aren't missing much, in my opinion.
I have that option tried it and was very irritated by it.
I turned it off.
The truck just isn't that much louder at speed than at idle.
I guess if you had a loud aftermarket exhaust it could be beneficial otherwise, it's like having an invisible kid in the cab with you playing with the damn ****.
I found myself constantly correcting the volume when driving in traffic. It eventually got the best of me and I ran off the road, leaped from the cab and collapsed in a heap, sobbing uncontrollably.

Go ahead and continue to try and hook it up if you want to but, if it was something I couldn't turn off, I would have sold the truck by now.

 

Raoul,

Train your sheep to leave the radio alone or make it sit in the back seat!

JMC

 

Thanks for the help. I think that for the moment I have gone to as much trouble as I want to try to make this work. It was just a minor thought while I was installing a cell phone anyway. BTW, that worked great through the factory radio cell mute and audio inputs (pins 10, 11, & 12).
Joe