Hello All :Some time back I posted a query about my Roadster overheating due to fan not coming on. Thanks for all the helpful responses. Now that the problem has been fixed I thought I would relate my experience as it might be helpful should anyone else experience a similar problem. (Reminder: I am a mechanical novice). So here is an update:
Bottom line is that, through a process of elimination, I figured out that the rheostat that measures the air temp behind the radiator had failed. Tried to find a replacement at several local auto parts stores without success. (None even recognized what it was).
Then discovered that there is a very small part number (I am talking about getting out the magnifying glass) under the coil on the back side, along with a similarly small Ford logo. Took the part to the local Ford dealer who had never seen one before but checked their inventory and had one. Walla! Apparently it is quite an obscure part.
So, if you ever have this problem here is the Ford part number: F5RZ*8L603*AC, described as a “Resistor A”. And be sure to save the pigtail from the old switch as it will have to be soldered to the new one and then sealed.
Oh, one last thing. After installing, when I ws running the engine to test the switch I could not get it to turn on. I stood there for 30minutes watching it (watched pot etc.). Finally figured out that because it was measuring air temp I needed to close hood (oops; bonnet) to increase temp. Closed hood and within 60 seconds it turned on.
Again, thanks to everyone for all the feedback. Next project, the oil pressure gauge.
John Stanley, Deland, Fl.