Ok, at lunch time I went out and played mechanic. I found two wires leading off the top of the A/C Receiver dryer (not the pressure switch), shorted them together and the fan switches on fine. I'm going to short them out for this evenings drive home and observe the temp. I think the main fan's fluid coupling might be ok but I may replace the whole thing with a plastic fan a different clutch (different, not new :-) . I'm betting the aux fan's going to be enough for me to manage the next two week's anyway. I did use a 50/50 mix of MB coolant and distilled water. when I flushed out the block and rad there was really no evidence of corrosion. Last summer the car ran fine even on very hot days. It will only go a tad over 100C. Even stopped in traffic it goes no higher. I'm going to perform a test on the sender and since it's cheap, maybe just replace everything.