Tach failure/quit
 

Had a battery go dead big time, jump to get home was tramatic on the system, lost the blower system and the tach. A new battery and the blowers work fine once more but still no tach. I checked the fuse and it was good, replaced it anyway, but still no tach. Does anyone have any ideas??

what kind of vehicle?

Tach
 

Sorry, not thinking. It is an 86 300SDL

afraid I can't be of much help.. the 124 cars have an OVP (overvoltage relay protector) that has a fuse that can burn out when a vehicle is jumped) you can perform search for more info. trouble is, I don't know if your car has an OVP, so maybe someone else can help you more than I have... sorry :(