2005 S80 Vent fan won't stop nor vary speed

[donf]

I'm not talking about the fan continuing for a few minutes after the engine is shut down.

The fan first started blowing only on high speed. tried turning it manual, no change. Stopped, continued. removed key, continued. waited 30 minutes, continued.
This lead me to remove the fuse. The next morning I replaced the fuse (key out of ignition) got a spark, fan ran at high speed for a few seconds then slowed down and everything worked perfectly for a few minutes. Then it started running at slowest speed but otherwise the symptoms are as above.

it's 106 in Dallas - I need working AC!

I see some posts referencing a 'resistor' but am unsure if it is on the blower motor or fan speed control. Doesn't seem to be a consensus. Also - is the fan under the dash behind the glove box or in the center console? (just did the same repair on wife's acura in the console - 15minutes! Don't expect to get lucky twice though)

Please help - need to repair this myself cheaply so I can keep my son's S70 on the road!

[jimmy57]

The fan power unit is mounted to the blower motor. It is a transistor circuit and either the transistor or the control circuits do fail on occasion