The A/C and ACCE belts on my 2004 300M broke. Picked it up this evening and now the tachometer is making strange noises. There was NO issue with the tach before the repair work. What could be causing this?

Thanks for any guidance you can offer.

 

Tachometer as in inside the car where the cluster is?
A belt repair would not have a single thing to do with it Id check the noise else where. Plus a tech is highly unlikely to make any noise.

 

Check to see if the hood release cable is rubbing on the alternator pulley.
Should be routed to a clip on the upper rad support but have seen them rub on the alternator.