M-20 Perkins Tachometer Calibration

[JusDreaming]

I had to replace the instrument panel after a lightning strike. I found a new complete panel with all instruments. But now I need to calibrate the tach., as it only reads 2000 rpms at full throttle.
I have various literature for other tachometers but none for the one I have. It is a Volvo Penta/VDO analog tachometer. And I think I need to adjust the potentiometer and the dip switches, but not sure. The diagrams I have do not match the actual tach. exactly. Any input from someone who is familiar would greatly be appreciated.
http://www.egauges.com/pdf/vdo/0-515-012-044.pdf is the only instructions I have.

[CampDavid]

First off is it a VDO Tach, should be branded VDO.
Second how many poles on your alternator
Go to VDO Siemens, that have a good two page instructions on setting the dip switches and calibrating.
Get a infrared digital tach and check the engine rpm then adjust tach to match.

You can do it or as others say " Just Do It"