after the capacitor, whart next?

OK, so I've changed the capacitor for Farnell 1781894 (325v), tried a 400v 1uf capacitor, swapped the relays round, no difference. It may run the compressor, often doesn't. When t odes, it only runs for a few minutes, then cuts out. What am I meant to do to get consistent action from the compressor relay?! Fan relay circuit works fine, I even swapped the two relays round on the pcb, but the compressor still won't fire. Is there a rogue component before the capacitor that's messing this up?

many thanks (in anticipation!)