Air Conditioning Problem

Robert Sprott

New Member
Jul 1, 2017
2
New Baltimore
Boat Info
340 Sundancer
Engines
7.4
I have a 1999 34 Sundancer. The AC works great for about 4 hours and then the fan motors turns off. The AC unit continues to work and a very light flow of cold air comes out of the vents. I turned the system off for a couple hours and turn the AC back on and it works great.
What would cause the fan motor to turn off after 4 hours? Thank you.
 
Check the unit. You might be icing up and shutting down.
 
The run capacitor on the fan could be bad. I'd start there for a measly $10. If that doesn't fix it, I'd look at the fan motor next.
 
If you are freezing up, make sure filter is clean and there are no obstructions to the air intake area. We once had a cooler setting in front of our intake and ours froze up. Moved the cooler out just an couple of inches, problem resolved. Also make sure someone didn't stick something in a compartment and close off one or more of the ducts. Restricted flow out will limit flow in. Also, stat may be slowing fan down. Make sure it is on manual and highest speed.
 
I've had mine freeze up a few times and each time it was on a very humid day and I had the set point at <70 degrees, so it ran a long time.
 
If it does freeze up again, set it to run the fan only without the compressor engaged.

This will thaw it out in just a few minutes.
 
I've had mine freeze up a few times and each time it was on a very humid day and I had the set point at <70 degrees, so it ran a long time.

Agreed.

The unit has to cycle on and off in order to avoid freezing and shutting down.

If you arrive at a 110 degree boat and turn the AC on at 70 degrees it will run continuously for hours and will probably freeze.

Best to chop the temp down incrementally allowing it to defrost between cycles.
 
Good advice so far. Just to amplify...

To avoid icing, make sure your air filters are clean and consider increasing the minimum fan speed for better airflow. Also, if the unit freezes, put it in heat mode. It will thaw quite quickly.
 
The one time I had freeze-up on a NEW dometic unit it was because 1) I had a large number of people sleeping on the boat overnight (heat load) PLUS 2) I reduced the fan speed to be set as low as possible instead of automatic. Make sure you let the unit manage the fan speed, or set it high enough especially during hot days.
 

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