I turned on the ac for the first time this year and was greeted by the blower fan running only half speed, and then turning itself off after about a minute. My first thought was to install a run capacitor for the motor, but it made no difference. The cooling fan for the condenser and the compressor are running when the blower quits.  

Any thoughts ?  

You are so fooked!

When the heat comes on does the furnance motor run full speed? The same fan (ought) to be the only one in the darn thing. Measure the voltage but I would assume its at 115VAC and that you've got a motor with some windings lost. Original motor? They're not exactly cheap but not too expensive if you've got the technology to install it yourself. A heating and cooling place ought to be able to test it if you bring it in and ofter to buy the replacement from them.

Or are you talking about the fan that helps pull heat out of the condenser's coils? Doesn't sound like it from your discription but this second fan sits outside on top of the coil stack.

Keep cool