Re-setting Service Indicator A-Class

Ive got a 2000 140 A and the service indicator has dropped to zero on a couple of occasions Ive had it checked and re-set but no fault was found .
The car is otherwise running perfect with 27000 mile on the clock any ideas
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file
Upload is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.