On Jul 30, 8:17 pm, wrote:
Dear Uncle
If your altimeter changes indications when you open the vent, that
indicates your altimeter is not connected to STATIC. Best to check
you plumbing.

Or (dramatic pause) it means that someone (previous owner?) has chosen
the cockpit as the static source. If this is the case, I think Mr
Fuzzy just learned why it's an excellent BACKUP source and a poor
primary one (hint-use a pneumatic toggle to switch to cockpit static
only when your REAL static system is waterlogged/frozen) Use your
ships actual static system. It works better than the cockpit.

My 2 Pesos,
-Paul