My a/c works fine. Get cold on the copper line. But blower is not working. Light is blicking slowly. What do I do?

Check with a meter to see if voltage is being applied to the blower motor when it should be running.

Hopefully my recent $450 repair from a similar situation can shed some light for others with blower problems. My blower also stopped working suddenly. The heat and condenser were working fine, it was just the blower not working. The motor tested fine and was drawing 7.1 amps when the tech bypassed the logic board. He removed the logic board and found it had arced across the back.

The board from the front
http://blogs.theshanks.net/wp-content/uploads/2010/08/Trane-Logic-Board-Front.jpg

The back of the board
http://blogs.theshanks.net/wp-content/uploads/2010/08/Trane-Logic-Board-Back.jpg

Where it all went wrong
http://blogs.theshanks.net/wp-content/uploads/2010/08/Trane-Logic-Board-closeup2.jpg

The relay that failed (big middle one)
http://blogs.theshanks.net/wp-content/uploads/2010/08/Trane-Logic-Board-Relays.jpg

I ended up paying $319 for the replacement board and a $50 pickup fee since they didn't stock it. The repair was only $89. In hindsight, I would have ordered the $169 replacement from My HVAC Parts (http://www.myhvacparts.com/Catalogue/Printed%20Circuit%20Boards/Trane%20XE80%20Furnace%20Control%20Board.htm) and swapped the boards myself.

The technician was very nice and did a great job but I think I could have done it. In order to test the board, he disconnected the black wire from the LINE-IN (the one coming off the kill switch) and ran it through a 30-amp breaker he had rigged up, the then connected the other side to the COOL-HI, my blower fan came on without a problem.

I can't seem to edit my above post so I wanted to add this was part number 50A55-571, the replacement linked above works with a wide range of Trane units, refer to the site if it will replace yours.

As always, unless you know what you are doing and have taken appropriate safety precautions to disconnect the circuit before servicing the equipment, don't do this.