blinking red light on Trane unit

[B]

In my attic there's a Trane central heat/AC unit. There's a round "window" the size of a quarter, and peering into that window I see a blinking red light. Whats up with that?

-B

[B]

I wasn't very specific, ... It's a Trane XE90, three years old, seems to be working fine (right now), and the red light blinks 2 times per second. -B

[TURTLE]

This is Turtle.

It is a diagnosis lite to blink and tell the tech what is wrong with it if there is a problem. If the lite is blinking about every 1 second apart and no changes in the pattern. It is saying Leave Me Alone - Leave Me Alone - Leave Me Alone.

TURTLE

[MLD]