Before digging down to the blower, I would do a simple regulator trigger voltage test.
At the firewall . behind brake booster, is the blower 3 wire feed plug. [red/yl/blk]The yellow wire feeds a variable voltage from the Control Panel to the regulator. This is how they control the speed. So, voltage across yl/blk at this connector should be variable from approx. 2-9 V. , depending on CP setting. Voltage across red/blk is 12v.at all settings. If OK, then your problem is down at the motor/reg. and the next test requires digging down there.
The test there is to jumper a wire from the blu wire of motor to ground w/key ON...that will result in HIGH blower..if blower is still slow/dragging, then the problem is dry/worn bearings or bad brushes in motor. If OK w/jumper of blu wire , then regulator is bad.[ this jumper test simply takes the reg out of the circuit..ie..by-passes reg. ]. The Red + 12V. at blower is always hot, so, as you can see, the switching of the blower is done on the ground side..ie, blu wire... [switched ground].....
These sequenced test steps will diagnose the culprit w/o guesswork.

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A Dalton