Heat pump seems stuck in defrost during heating mode

by Frank
(Phoenix AZ)

I have an old Goettl (4.5 tons) packaged unit it had a shorted defrost board. I replaced the ranco dt2 with an ICM-307c. It worked fine during the day in heating mode but right around 9:00 PM it went into defrost mode and did not get out of it. Checked (OK) outdoor t-stat by sticking it in the freezer it had continuity and it would lose it at room temp. The reversing valve solenoid also seem to be working. I could hear RV clicking if disconnected while the unit was running. I may add that the unit works in cooling w/o problems (unit started acting up at the end of heating season last year). Any suggestions? Thanks

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