Intermittent Cruise Control

[tobodestroyer]

Hi,

My Cruise Control only seems to work intermittently. I've narrowed the problem down as I've spotted that it only works when the computer is displaying the current MPG correctly. It tends to stick at say 5.0 mpg for a few days during which time I have no Cruise Control. Is this caused by a dodgy engine speed sensor? VAG COM tells me that G28 is working intermittently (with engine running) or am I barking up the wrong tree?

[madpugger]

I would suspect it is a speedo sensor in the gearbox as the cruise uses the speed as its reference, I know this as I changed gear without clutch or knocking off cruise to see if it used the rpm or speed, just out of interest.

The fact the MPG doesnt work right either would suggest the same....

[S2central.net]

Cruise control just modulates throttle position to maintain same road speed - it has no clue about engine speed.

A bad signal to or from your speedometer could cause funnies with cruise control... likewise that would throw off your trip computer.

[Tonks4x4]

Check the switches on pedals as if they are loose or not quite in the fully pushed in position it will cut the vacuum.

[mcandmar]

Pedal switches are troublesome, easy to test with a multimeter and length of vacuum hose. The vacuum diaphragm can also tear with age and cause this.

From reading above it sounds like a dodgy speed sensor if its effecting the onboard computer too. Its the vehicle speed sensor on the gearbox, not the engine speed it uses.