Recently fixed my home AC, pretty sure the contactor was screwed and the capacitor was done for. Just poor maintenance by the previous owner. Bought the parts, rewired the thermostat because it was a nightmare of cables in the furnace, and in the process blew a fuse and messed up the transformer in the furnace. I didn’t have a replacement fuse so I jury rigged a bypass for now, got a new transformer that I tested and validated the output on, along with everything else in the chain, new contactor, new capacitor, and a completely rewired thermostat. Took a few days to fix.
In the process, I picked up an extra contactor, and capacitor, for the next time these parts inevitably fail. I need to go back and re-test all the parts, I suspect some may be ok, given that the wiring was such a mess, but I have no idea. I know the cap was definitely bad (bulged and leaking), but the rest might not be broken, they may have been malfunctioning by proxy of the bad fuse and wiring in the furnace.
Apart from fuses, I have everything and spares, so if I can validate that the transformer works, or the contactor is fine, then I’ll have extra spares. No worries.