C5 Cruise Control

fred1 · Unread post by **fred1** » 06 Apr 2006, 19:33

Any one any experience or knowledge of C5 cruise control problems/wiring/operation?

Mine has just started to operate intemittently. That is it works ok on one journey and then on a restart it does not. Obviously could be poor switch connection either on control or on one of the deactivating inputs (brakes etc) or an ecu problem ?

Any ideas or suggestions?

C5 is a 2002 2.2 HDI exclusive

AndersDK · Unread post by **AndersDK** » 06 Apr 2006, 20:58

The cancel input is taken from the brakes (stop) lamp bulbs +12V side.

When cruising the bulbs are not lighting up - and acts as a low ohmic path to earth. Only when +12V feed is applied by braking the bulb lights up and the cruise cancels.

Now say if you have an intermittent earth to the stop lamp bulbs - then the cruise control loses its earth and will most likely cancel. Same happens if the feed wire to the bulbs for some reason is intermittent.

My point is : start with the simple things

PS : could be a cancel switch too on the clutch pedal - donno - but have a look.

wheeler · Unread post by **wheeler** » 08 Apr 2006, 13:45

if its an early C5 then it will have a seperate brake pedal switch ( red in colour) for the cruise control only,later models have a dual function switch.they send an earth to the ECU to cut out the cc if the brake is pressed.the switch is located on the brake linkage behind the glovebox at the passanger side (assuming its a RHD),if that doesen cure it id replace the clutch pedal switch next.

fred1 · Unread post by **fred1** » 09 Apr 2006, 16:11

Thanks guys. Having a "way in" on how the system works is always a big help. I will investigate and report results

PowerLee · Unread post by **PowerLee** » 09 Apr 2006, 16:31

Not an C5 estate by any chance?

Water in the rear lights is worth checking for