Hello,
Not sure if this has been asked before, but why is my cassette type analog tacho showing an exclamation mark on the bottom line and flashing the clock?
Any help much appreciated!
The time has been adjusted, take your chart out, close the drawer and it will reset itself
if you have a blank chart in the bottom of the tacho (driver 2 chart) remove this also, close drawer and it will make a grinding type of noise then open and reinsert your chart hope this helps 
any probs just pm me
take the clips off 
And don’t leave a blank chart in position 2 of this type of tacho, it isn’t required and by not having one in there you won’t get this sort of problem.