heat pump fan reversal

Bryant 517E inside and 661CJ024-B outside unit.
i have observed that;
when fan is blowing air down, there is frost on the outside.
when fan is blowing air up the coils have less frost. this lasted about 15 minutes, so I suspect this is the defrost cycle?
is this correct for this unit?
Thanks! -Giles
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Frost is usually a good sign that you need to call an a/c guy. Condensers will frost when over charged and under charged. Call some one soon.
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Actually, frost build up is normal on the outside unit of a heat pump. The defrost control will defrost if the coil temperature is below freezing for more than a predetermined time (1/2 to 1 hour). The outside fan should be OFF during defrost. The inside resistance heating should be ON and the inside fan should be on during the defrost cycle.

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Down?
Frosting is normal, depending on humidity and temps. When a heat pump is running, many people assume wrongly that the frost indicates a low charge condition. Not so. Its the reversal of the fan thats getting me....somethings out of whack there...
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