Pulling the cluster on a 126 chassis is one of the easier models.
If you decide to do this, you might take it a step further. We find that almost all tach failures are either bad solder connections or bad capacitors (available at radio shack). Just replace them all. If you are planning to chuck it you might as well give it a try.
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician