I just bought an F700BT, and I'm reading up before I try to install it this weekend. In reviewing the installation instructions and this forum, I learned all about the VSS connection and what it's for. But in the installation manual that also covers the F900BT, it says, "Pink (CAR SPEED SIGNAL INPUT) This connection is unnecessary for AVIC-F700BT....Always connect the vehicle's speed detection circuit. Failure to make this connection will increase errors in the location display."

So I'm happy that this is one less step for me, but I was wondering why the F700BT doesn't need this connection, while the F900BT does.

Also, is there any reason why I should make this connection anyway?

The reason you shouldn't make the connection is because you can't make the connection. There isn't a wire coming out of the 700BT for VSS be it used or not.

It makes the unit slightly less accurate but I can't really see how much more accurate it could be.

It has to do when gps sensor data is lost, going through a tunnel long tunnel or in any other area with low gps signal. This allows the unit to keep better track of where your at and how far you traveled. Without it I am assuming it will correct itself when a signal is reaquired.

There is a video on the D series that explains the concept of gyro's and accelerometers in the navigation units and the vss wire. I am sure its on youtube.

Prior to installing my F700BT I used TomTom 720. I went to Boston and driving in the tunnels there it was very accurate. Given that speed wires were not hooked up to it, my guess the 700BT won't miss it as well. Makes you wonder though, if it didn't provide any benefit, the 900BT wouldn't have it, maybe in low reception areas it works with satellites to improve the accuracy, but my guess the results are only marginally better.

A VSS connection is used by the nag system to perform dead-reckoning. Along with the internal gyroscope, the system can calculate current location based on the pevious known locationl and instantaneous velocity.

It mostly comes into play when there is no GPS signal, and all portable nag units make do without a VSS connection.

We went though this same discussion 2 weeks ago when I bought my F700BT.

http://avic411.com/forum/viewtopic.php?t=18791

The wire is indeed missing from the harness.

The accuracy is OK... But nothing like my old Kenwood with a VSS wire.

The nav software pretty much sucks anyway so you won't notice it.

The reason you shouldn't make the connection is because you can't make the connection. There isn't a wire coming out of the 700BT for VSS be it used or not.

Doh!

That will teach me to ask questions before looking at the cables themselves.

Thanks for the info.