You will probably get a check engine light soon. When the ECM sees a problem with the thermostat or temp sensor, it runs the cooling fan as a failsafe measure. Replaceing the t/stat and sensor will probably fix your problem.By the way, volvo thermostats usually crap out shortly after 60k.To quick check the ECM side of things, unplug the temp sensor (located in the thermostat housing) and start the engine and measure the voltage across the harness side of the conector. You should get 5 volts. If so, the wiring to the ECM is probably ok. Most of the time, the t/stat sticks open, causing the problem you are having. I usually recomend replacing the t/stat and sensor together as you have to remove the t/stat to get to the sensor anyway.