I had the same experience with my '86 4kcsq. Replacing the
radiator fan relay was the solution.
You might enjoy(?) the whole story. I found the car at a
dealer. I checked out the car myself and also had an independent
import garage inspect it for me. There were a few things wrong,
but nothing major. The dealer dropped the price, and we made a deal.
I knew nothing about the radiator fan problem yet, evidently it was still
an intermittent occurrence and had slipped by everyone. Everyone except
the dealer that is, whose solution was to UNPLUG THE RADIATOR FAN on the day
that I picked up the car!!!!! Needless to say, I didn't get very far
before overheating and blowing out some part of the ac system (this was a few
years ago, I'v forgotten some of the details). I pulled over immediately,
found the rad. fan unplugged, spoke some french, plugged it in, spoke some
more french, and then went on my way. No engine damage occurred, just some to
the ac system.