Hard-start kit

A hard-start kit is a small add-on — a start capacitor plus a relay — that gives an AC compressor a bigger jolt of starting torque than the standard run capacitor alone provides. It genuinely helps when a compressor is struggling to start for a fixable reason: a weak run capacitor, marginal supply voltage, or a long refrigerant line set. The catch is that it can also just force a mechanically failing compressor to keep starting, masking a unit that's on its way out rather than fixing it — so the honest use is to diagnose *why* the compressor hard-starts first (test the capacitor, check voltage) and fit the kit only if the compressor is otherwise sound. Fitted blind on a dying compressor, it buys weeks, not a fix. It's a cheap part, but a stored-charge electrical component, so it's an electrician's / AC tech's job — see the fuller hard-start-kit discussion.