VSS - vehicle speed signal

[Bowlerwell]

"vehicle speed signal - commonly found as white/blue cable"

Can anyone tell me what voltage output correlates to what speed?
I want to test my cruise control system.

THanks.

[johne]

It doesn't directly. The VSS signal is a set of pulses of constant +5volt amplitude, the greater your speed the more pulses per second.

John

[rs200]

99% of problem on cruise control are 2 vacum swiches on clutch and brake pedal.. or vacum pump on throttle .. forget on VSS.

[Bowlerwell]

Thanks John.
So it's a PDM signal where frequency varies with speed, rather than DC voltage changing with frequency.

Thanks!

[S2central.net]

I did some brief tests on it in the past to get an idea of pulse frequency vs speed. Cannot remember any of it but posted results here somewhere. I'll help you look for it if you cannot find it.

[Bowlerwell]

Thanks Paul.
I'll search more.

[4WheelDrifter]

There's a magnetic/plastic ring on the output of the front diff, that runs by a reed switch in the transmission speed sensor (VSS). The reed switch is either open or closed, hence the 5V pulse. The pulse will be linear to wheel speed.
It's a long time since I looked at the magnetic ring, so I can't say whether it's 1 pulse/rev or 2... A multimeter on the VSS while you turn the wheel should tell you.

But as said above, you should check that the vacuum switches on the pedal are located properly, and are working first.

[Bowlerwell]

The CC is not on the car, I want to test that it is fully working before I fit it.

[mcandmar]

In my experience the control stalk is the cause of most problems, but its easily disassembled to clean the contacts. Test each function with a multimeter to be sure its all working as it should.

[Bowlerwell]

Yep, will do.
If I want to replace the rubber tubing, where's the best place to get new tube?

[mcandmar]

Any old vacuum tubing will do, just go to your nearest motor factors and buy a length of it. I had to do that myself as the kit came from a LHD car and needed extended.