Rich wrote:
: Tach cable is relatively cheap to replace, but difficult to thread
: through the firewall and behind the panel. New tach is easy to replace
: but more costly, and will add confusion to future record keeping in the
: logbooks.

If you do decide to replace the tach, any reputable instrument shop will be
able to reset the tach hours readout to what you specify. I wouldn't be
concerned about confusing the records in that manner.

I would try to borrow a known good tach, perhaps from your mechanic, and
plan an early flight on a cold morning to see if the problem changes.
--
Aaron Coolidge