Originally Posted by Yak

Unless you're going to replace the seats, I can't really think or a way to re-connect the actuators to a mechanical lever. I didn't think fixing the vacuum was that big a deal. I agree on the safety aspect, though. A folding seat in a collision seems bad.

For troubleshooting mine, I started at the seat itself with a Mity-Vac: do the actuators move with vacuum applied? If no, fix them; if yes, move upstream. Then under the hood, with the window open and the doors closed: using the Mity-Vac on the check valve on the blue line only (and a lot of pumping) do the locks engage? (You need the window open in order to check without opening the doors since that dumps vacuum; I forget if the ignition needs to be on, but I don't think so.) If so, then the leak/problem is probably in one of the other systems - A/C or central locks - and those systems are preventing forming enough vacuum; if not, then the problem is in the blue line. It might be a sticky door switch, since that electrically dumps the vacuum relay, or the relay itself (you could remove the relay completely and the seats would lock, but not conveniently auto-unlock when you open the door).

My seat backs didn't work except in defrost, until I fixed that A/C pod. I had a little routine of starting the car, selecting defrost and waiting for a screech of the seat back springs rotating, then selecting normal. Once they're locked they stay locked via the check valve unless vacuum is dumped by opening the door, pushing the seatback button, or it leaks out.