02 hvac fan/blower acting up?

[57chevyragtop]

3400 02 imp...heater blower started acting funny early cold morning yesterday vibration mostly. Then this morning it started working ok then quit on setting 5 (hi) but would work on 1,2,3,& 4 and intermittant on high. After full warm up I parked for an hour at my appt. And on restart all worked fine. It had been rainy for 2 days prior to below 30 degree day of yesterday Dec.3
Any of you have an idea what this could be, I know all the air comes through the outside filter in that setting. Frosted filter maybe?? (blocking air flow) filter is new this year and no leaves or trash blocking. All thoughts welcome

[maxwedge]

Sounds like 2 issues the vibration is debris in the fan or the motor is going bad, the speed issue is usually the resistor relay pack mounted on the blower case behind the glove box area.

[57chevyragtop]

Sure hope it's not the blower motor $170&change... at the dealer. Probably less at other suppliers...salvage if I must. But seems to be working ok now. Thanks for the resistor relay pack info. I was thinking something like a overload resistor in the circuit. I will look for debris tomorrow if we don't get the snow called for here tonight & tomorrow and check the filter as well.