Hello.
I bought a house with central air, tried to start it up the other day, it ran, but the condenser fan would not shut off, only way to stop it was to pull the disconnect outside.
I removed the cover and found the contactor, it looks to be in pretty good shape. Someone tie-wrapped something to keep the contactor closed or pulled in, and upon further examination, found that the 24vac wires from the air handler were not connected to anything at the condenser. I have spent about 14 hours looking on line trying to figure this out, with no luck yet.
Please help

What's the model and make of the units? Manufacturer's Installation Manuals are sometimes available on line and include wiring diagrams.

If the 24V cables are out then there's no control communication between the air handler and the condenser. It's usually a simple job so try and get the manual.

Check out how much for a service engineer to fix it. It shouldn't be too much and he'll set the whole thing up for you.

An important thing to check is the refrigerant you're using. Is the condenser R22? This is nothing to do with the wiring but has to do with the use of R22 which, in the UK, is outlawed from 2015.