blinking red light on Trane unit

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
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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

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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
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On my Trane there are two lights-red & green. The green light blinks relatively slow when there is no demand for heat and much faster when there is a demand for heat. Normally, the red light blinks about every 20 sec or so. When there is a problem it is the one that is used to interpert any diagnostic codes. This is spelled out in the furnace manual. Suggest you read yours or find it at the Trane site for more specific information. MLD

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