Update - was able to solder on the new regulator to my old harness today. Takes a pretty strong iron to do it but I guess it was ok. Plugged it in a tested it on a "new" motor from a late w124 - smaller diameter from mine. Plugged it in and it ran full speed all the time. Reckoned the regulator was bad after all and said some nasty words. Then for some reason, I had the idea I should test it with my old (almost seized) motor. And it spun in different speeds. Ok - regulator works. Hurrah! Need to look for a new (similar) motor tomorrow! Regulator is back in the car - much easier getting it back in. I have connected an extra set of long cables so I can test motors directly without having to take anything apart.

Here are the two regulators
Old one - 1248202710 at the top. New one 9140010153 at the bottom. New one had only 4 cables but was made for 5 - one extra red cable
https://www.dropbox.com/s/v0q38owadbny5qj/File%2003.08.2016%2C%2023.28.13.jpeg