Disappointing Prebuy

[Skymaster337B]

There's only one way to check pressurization...climb to FL200 and see what the cabin pressure is. This not only checks the cabin's ability to hold air, but the turbo's ability to make air and keep the engine's manifold pressure up.

I'd ask the sell if he's willing to discount the money you wasted ($1500) as a matter of good faith if he wants you to come out to see the airplane again...after everything is working for the second time.