Hi, Art - You are quite right about the driver's door switches being the prime suspect in central locking failure...in fact that is what is plaguing my son's 81 right now. (I'll get around to it once I unearth the right box of PnP treasures). Good to know the wiring colours and layout stayed the same over so many years.

My suggestions above were based on the OP having been under the dash to repair a blower motor, which led to the thought that he may have disconnected a wire. A quick check would be to unplug the connector shown as "S" in your P105 diagram, and check for 12V with a voltmeter on the Red and Green wires coming from the relays (not from the door). No voltage means something has come adrift under the dash, or fuse has gone (does interior light work?). If OK, briefly short, with a paper clip or such, the black terminal in that connector to the red, then to the green. If the door locks operate, the problem is then isolated to the driver's door switches or wiring.
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Bob: son's 81-GL, dtr's '94-940, my 83-DL, 89-745(V8) and 98-S90. Also 77-MGB and some old motorcycles.