Wacko AI

My XP Hawk didn't have a filter upstream of the pump until I had to overhaul
the AH and DG, with carbon found in each instrument. I had a vac 'pump'
failure some time previously. Hopefully the filter doers the trick during my
next vac failure.

--

regards
Ron



"Morgans" wrote in message
...

"Mike Noel" wrote in message
. ..
OK, we now know the problem was a pinched hose, but there is some
speculation that a failed vacuum pump can actually blow dust backwards
into the vacuum instruments. The idea is that residual vacuum at the
instruments allows the higher pressure at the failed pump to push the
dust into the vacuum instruments. There is an STCd filter that can be
placed between the instruments and the pump designed to prevent dust
backflow if the pump fails.

I thought vacuum systems had a check valve that prevented backwards moving
air. No?

If not, it sounds like they should.
--
Jim in NC