I had my taxi meter fitted and they took out the dials to fit the pulse wire, then put everything back, last night and tonight I noticed that the left hand indicator arrow was dimly lit, this is with the lights on, and the low oil warning also, turn the light to side light they both go out, could the fitters have dislodged something???

I did check the oil level just inc case and its fine at the top mark

Take it back

yes defo take it back, mine works absolutely fine everything is illuminated and no warning lights except the washer fluid which was empty so filled it up and it went off, no faults here with the meter fitting