A certain passenger, (who shall remain nameless for fear of me having my hard won bank of house points confiscated) has a habit of fiddling with the radio, heater/AC controls and the fascia air outlets when she is riding shotgun.
On two occasions, during her finger safari across the dash controls, she has somehow managed to reset the computer trip. Fortunately, it was showing distance Trip B at the time and not the fuel economy trips which I keep records of.
I have therefore mounted a guard around the vulnerable button, which is made from a back delete key off on old computer keyboard with the centre removed. This is glued to the dash with a temporary adhesive.
It is now necessary to make a deliberate effort and poke a finger within the recess to operate the trip button.
Job done
