ticking over erratic

First off, i have a 2004 SX 1.4 Sensodrive. Ever since i got my C3 last year, when the car is turned on and is left to just tick over, the car revs itself with out any input from me, and as it does so the lights go brighter as it revs and duller as it goes back down.

It just past its MOT again so i guess its nothing major, just wondered if thats what all C3s do.

when the car is turned on and is left to just tick over, the car revs itself with out any input from me, and as it does so the lights go brighter as it revs and duller as it goes back down. It just past its MOT again so i guess its nothing major, just wondered if thats what all C3s do.

They shouldn't do that.

The tickover is controlled by the ECU and its detected as too low, so the engine revs up. The lights brighten because with more revs, the alternator can deliver the power needed. When the revs drop down the lights dim because the alternator can't produce enough power because its rotating too slowly.

The MOT test checks for safety, emissions and some compliance, its not a check to see if the car will last the next 12 months.