I can switch two independent autopilots to the drive and have a spare drive that can be swapped in in a few minutes. I also carry spare course computers, spare control heads, and a spare compass for my ancient Autohelm 6000. I have swapped drives twice while crew has hand steered the boat.

A long time ago, before I carried a lot of spares I had a fluxgate compass fail. Not knowing what the problem was I sent the entire autopilot back to Autohelm. They returned it to me with the exact same problem. I ended up finding the problem myself just by tilting the compass. Found one of the fine wires to the fluxgate had broken. Just barely managed to fix the incredibly fine wire which lasted until I could buy a replacement compass. When I phoned Autohelm to demand a refund for the repair bill the technician told me that he doesn't have time to tilt compasses. I said if he tilted compasses mabe he could fix autopilots. They refunded the bill.

That is not a typo. This was before Raytheon bought Autohelm. Other cruisers told me they sent a course computer to Autohelm with a note inside. It was returned, supposedly fixed but the note was inside, untouched - and of course not repaired.

If you go to sea you must carry spares or be prepared to live without it.