Air conditioner makes heat, but fan is not acting right

LaRea

Probably a question for you Great Lakes boaters who actually use heat.  The main AC unit in the salon works fine for cooling, but it does something odd when set to heating.

For 5-10 minutes, it will create tons of heat with the fan running at medium.  Then the compressor shuts off and the fan turns on full blast for about about 15 minutes, blowing room temperature air.  It's not chilling the air, but the breeze is uncomfortable for anybody sitting near the vent.  Then the compressor comes back on, the fan goes back to medium, and it produces heat again.  Rinse and repeat.  

It's either full heat, or full fan with no heat.  Nothing in between.  

PickleRick

Is this a reverse cycle correct?   Wouldn't happen to have a pressure gauge on it would it?   A pressure spike could indicate an issue with the reverse valve 

TonyG13

I don't know if this helps, but this is from my Dometic controls manual (page 10):

"P-13: Reverse Automatic Fan Speeds During Heating The automatic fan speeds can be reversed during Heat Mode to improve heat output in cooler climates. The fan will speed up as the set point is approached. Lowering the fan speed when the cabin is cold increases head pressure and helps raise supply temperature. Increasing the fan speed as the set point is approached also reduces unnecessary high pressure faults. The fan switches to low speed when the set point is satisfied and the heating cycle terminates. The fan can be programmed to operate the same as in cooling by programming P-13 “nor” which represents normal fan operation during reverse cycle heating."

I've also attached the manual for reference.