This fan is a adjunct to the new (at least back then) refridgerant system in the '92 (maybe '91) to '93 cars.

You need to know that it is NOT controlled in any way* by coolant temperature. The sensor that controls it, a pressostat, is solely affected by line pressure in the A/C system.

Also realize that it rarely runs: you will only see it turn on if your stuck in stop-and-go traffic on a really hot day, and your A/C is going full blast -- then you might hear the roar of the fan trying to lower the A/C system pressure.

But to test the system (pressostat, relay, etc.), you can take the electrical connector off the pressostat and jump it with a paper clip -- the fan will roar to life. I don't know where it is in your '92, but in my '93, you'll find it beneath approximately the oil filter and somewhat behind the alternator, at the level of what looks like a frame rail (Volvos are really unibody, but it looks like a frame) -- if you take off the splash pan and look up, you'll see the A/C lines and a short branch off the line ending in a plug with an electrical cable attached. That's it (but as I wrote, I can only attest to the '93 cars).

[ * I wrote an article, published in Rolling (the VCOA's magazine, "Improving the Auxiliary Radiator Fan", 25(4):25, July/August 2007, pg 25.) that shows how, for only $7 in a short Volvo cable and about 15 minutes of your time, you can also make the fan turn on at high coolant temperature but ONLY IF you have the Nissen radiator with the temperature sensor built-in. Otherwise, it's too much work to be worth modifying the OEM radiator.]