Why did I know you were going to ask me that?
The blank switch plate next to the ECC unit has a grill in it. The temp sensor is behind that. BUT, it doesn't pop out. Pull out the radio and balance it on the shift knob, then grab the ECC unit from underneath and behind and pull it out - that usually takes a little force the first time. Unplug the ECC unit and put it on the floor, then push the radio back in.
Now you can reach behind the temp sensor. There are 2 small plastic tabs in the top and bottom of the round cylinder next to the grill. Push them in and pull towards the front of the car. Be very careful, the small copper sensor is very fragile and cannot be bent, and it sticks out of the plastic.
Clean the small fan blades, I used a round toothpick and q-tip, getting all of the dust bunnies out and the blades turning freely.
Putting the sensor back is a challange, there is very little room to work with. Once it is plugged back in, shove the ECC back in and start the car.
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My name is Klaus and I am a Volvoholic.