During startup, does the fan start and then turn off? The ECC unit is smart enough that it will not turn the fan on until the coolant temp starts to rise. Of course, if you move the fan speed switch, that overrides the ECC and makes the fan run.
There should be codes in your B-1 slot. Check them and post back. Milage has nothing to do with a heater fan. Just dirt in the intake will make a difference. You should install a cabin filter if the car doesn't already have one.

Klaus
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The 164 has a new home, all I am left with are a 95 854T and a 98 V70R :)

You can easily remove the cover under the glove compartment and try tapping on the motor. The brushes tend to loose contact with the armature when they get worn because the wire gets tight and prevents them from moving in the holder. This may be agrevated by the cold weather. It's quite a hassle getting the motor out but it does come apart easily. The brush wire can then be unsoldered and slipped a little allowing the brushes more movement. Otherwise you'll need a new motor.

Pull the codes from socket B-1 and post them back. Do the A/C and REC lights flash when you first start the car?

...Lee

when its working, does the fan blower make strange noises - rattles, grinding noises, squeals, or squeaks? Are these noises only present during turns?
Is so you probably need a new blower. This is what happened to me.