I just installed a new blower resistor in my 89 B2200 and on fan speeds 3 and 4, there is a whistling noise from under the dash. I have gotten upside down on both sides and cant feel any air leaks but it's that kind of noise. Trying to avoid pulling the dash and the HVAC so has anybody else ever dealt with that kind of a noise? Thanks

 

I've had a 1988 B2200 since 1994 and have had to replace the blower motor several times due to noise/bad bearings. I've had to replace the blower resistor exactly once.

So I would discourage anyone from removing the dash unless absolutely necessary. Could something be stuck in the blower motor squirrel cage???

 

I actually replaced the fan motor at the same time I replaced the resistor. Old one was very hard to turn from sitting up for years. The replacement I got at pullapart and before I installed it I ran jumpers to it straight off the battery and it didn't whistle. So as of now that's the only thing I really can rule out. I'm gonna get serious with it this weekend. Thanks for your input Cusser!

 

You can actually pull the Mazda fan motors apart and saturate the felt washers with oil to help keep the brass bushings lubricated. You have to be careful with the parts as you pull it apart, but it will extend the life of the factory fan motor.
I have pictures of this.....somewhere!