I have a FIAC Airforce 3phase AF17/200 compressor.
About 2 months ago it would not build pressure above 2bar (it usual runs at app roc 10bar), this was sorted as i got a service pack and replace the gaskets and seals.

Its been fine since then but now it gets to 11bar blows the relief valve down to 9bar and then just keeps running like that. It won't hold pressure at 10bar.

Does it sound like the relief valve is faulty or something else?

Cheers