Hi all, new to forum so just testing the water. I wonder if anyone can help, I have a A class 160 cdi 2006 and on tick over the engine speed fluctuates between 700 and 900 rpm and get a slight vibration from engine. This only happens if under load, I with lights and or heater on. When I switch load off it returns to normal. I have had battery check at Halford witch came back all good. I would appreciate any help with this matter as it's driving me crackers. Thanks in advance.