I need the groups collective wisdom. My DG quit adjusting and I got a good used DG ( Sigmatek) 4000B30, the identical unit that was in it. I switched them out and now the used one is doing the same thing ,and the one I took out will now adjust by the knob as it should. I ran up the plane and suction is at 4-5 and the DG is stabilized, just not able to turn the knob to match up to Magnetic compass. Not exactly sure what going on here. don't think I did any damage to the newer one installing it. Pretty straight install with the two vacume lines. I guess i could have two bad units, but the fact that the one I took out will now adjust has got me puzzled. The newer DG was adjusting before installed. Any thoughts other than just going glass and being a lot lighter in pocket book. This is for VFR flying by the way.
