I just started to feel a vibration from the blower motor when set to the highest fan speed. You can feel on the brake pedal and somewhat on the dash. On the other settings its fine just on high i get the vibration. I always run the blower on high. Is it time for a new blower? thanx

 

I don't know much about the specifics of a truck fan, but I know PLENTY about vibration, expecially rotation induced vibration.. Squirrel cage fanes (likely kind in the truck) are factory balanced. If you ever take one apart you will see metal clips on various blade.

You may have tossed a clip, or got some bearing wear. maybe a fan motor mount is loose. I plead ignorance on the exact configuration.

One thing... If there is an obstruction, it can cause pulsations in the air flow emulating an imbalance in the fan.

Vibrations is my life ...my love.