Fan continually runs '90 80

[Al Streicher <zeus@ior.com>]

On a road trip last night, I noticed that the temp gauge kept dropping
back to cold some time staying there. When I got home the fan would not
come on the cool the engine, as it usually does.

Today I checked the cooling fan. It runs as soon as you turn the key to
run. I checked the relay but it tested OK. I drove the car to get to
normal operating temp. Gauge still reads low and the fan ran while the
key is on. However, it still does not come on to cool the engine when it
was hot.

What is wrong? There are two little sending units in the water housing.
I believe one is for the cold start valve. The other? Bentley manual on
order, but wouldn't you know. Will it hurt to drive with the fan on.
Outside temps in the 60's.

BTW, the fan/temp gauge worked OK on Sunday.

Thanks.
Al Streicher