I just did an R&R on my van twice today so I thought I'd point out that the Four Seasons blower motor replaces clockwise and counter clockwise motors.

On my van the Green wire is power and the black is ground. I connected green to red (motor) and black to black and got weak fan output.

For the 1991 you have to reverse the wiring (green to black and black to red) to make it spin in the correct direction.

Be sure to check for proper rotation before putting it all back together. There is a rotation arrow on the back of the plastic fan.

Steve