92 GC heater fan - high speed only works

Just all of a sudden one day, only top fan speed works. Took out the controls from the dash, checked out the switch, don't think it's at fault. The fan I assume is just behind the dash, but taking off the dash is driving me nuts. Have all the screws out I can get at, and it's all loose but seems still to be held by something behind (?) the ashtray, which I can't get out.

Any advice much much appreciated!

It sounds like the blower module behind the glove box has shorted out. There are 2 small bolts that hold it in place, remove these and disconnect the wires and replace it. The part is not that expensive.