I have a Trane heatpump that is about 12 years old. In the summer it
cools fine.
Last winter the house was about 2 deg cooler than the thermostat was
set for. Noticed the inside air handler was running,but the outside
unit was not.

Checked and had power. The relay that puts power to the compressor and
fan was not pulled in. The coil did not have any voltage on it. The
circuit board has a led that blinks once per second like the paper in
the pump says it should if everything is ok.

I cut it off by the thermostat and then 5 minuits later turned it on.
Everything is working fine now. The heatpump did that to be about 3 or
4 times last year. I don't recall the temperature then,but today it was
about 40 deg F outside. It was 66 inside instead of 68 like it was set
for.

I don't mind calling a man for service, but there would not be anything
I know of for him to find. Any ideas on why the outside unit will not
cycle off and on like it should ?
Maybe it goes into the defrost mode and gets hung up ?