1998 V70R
The engine cooling fan does not turn when engine is at hot temperature. I checked the following: fan spins freely by hand, fan runs when I jumper 12v directly to the fan plug (both speeds), 12v is OK at input to fan relay, with engine running and AC on there is no ground signal to the input of the relay (either wire), with engine running at hot temp there is no ground signal to the input of the relay (either input wire), when I ground the "fan relay ground input" the fan runs (both speeds), and temperature gauge functions normally in instrument panel. At hot engine temperature, when the fan should turn on, there is a fairly loud "jet engine" noise for a few seconds then shuts off - but still the fan does not turn. I'm not sure where that "jet engine" noise is originating from. What resistances should the coolant temp sensor read at cold and at hot? Are there any tests that can be done on the engine computer to look for a ground signal going to the fan relay? Where is the engine computer located? Any suggestions would be greatly appreciated. Thanks!