Problem solved loose fitting 4-way connector at check valve before firewall. Car is a 83 300TD, sorry I thought that automatically came up when I posted.

I borrowed back my FSM and found test procedure for the master switch:
block off locking and unlocking line connections and then connect tester to middle, suction line. If it holds vacuum unit is ok -- which mine did.

Next I tested suction line from after check valve to driver's door (line plugged) -- held vacuum so the hard to get at check valve under the dash was OK. I reconnected lines to master switch and was able to actuate locks by applying vacuum with tester and moving the plunger on switch in and out on both sides of the check valve.

So I figured problem must be before check valve. Tested connection at brake booster line -- plenty of vacuum. Tested for vacuum at the 4-way connector -- very weak vacuum. Since I didn't have a spare I was able to get vacuum back through check valve and get locks to work.

Now, I need to order some connectors. I noticed that the car in the ifixit tutorial that cooljay mentioned has two yellow check-valves before the firewall. I only have one with two outlets but am wondering if there should be another one for the ignition vacuum lines (brown and green on my car)?

Thanks for your help everyone.

Jim