Relay failure ?

[Dave Conner <conner@cfm.ohio-state.edu>]

I'm puzzled by a recurring problem with the rad. fan on my 86 4kq.

Awhile back the the fan kept running until the battery died.
Later it seemed to be running too long again, and I got it to shut off by
tapping on the fan relay.
Sooo....I assumed it was a stuck relay and swapped it with another one.

The fan relay is the same one used for the horn, A/C, and a few other things.
I've tried swapping other relays from the horn, etc, but eventually the
same thing happens...the relay sticks.

All the other relays I've tried have been used, but I figured the horn
relay would actually have seen very little use.
Would a >new< relay solve this?
Or could there be some other reason more than one relay is exhibiting the
same behavior?
Any ideas?
Dave C.
Columbus, OH 

89 200Q
87 5KS 
89 100E 
86 4KQ