Cessna 340 pressurization problems
 

My 1978 340 just came out of annual inspection and pressurization won't go higher than 1.5 psi. Any ideas? Was fine before.

Take it back to them so they can ground pressurize it and find the problem. If it was working properly before the inspection, then something probably either got put back together wrong or was damaged. 1.5 PSID isn't gonna help much!

If you are interested in doing a bit of troubleshooting yourself start with the right side emergency window hatch. This is supposed to be removed at every annual but is notoriously hard to get back in with a good seal.

You can check it in flight by placing tissue around the edges. If there is a leak it will get sucked into the crack