Steve- we just returned from a trip in upstate NY on our 1981 56 Hatteras MY. The mid stateroom air seemed to work properly the first night, less so the second and virtually not at all the third. What is odd is the air flow out of the discharge was virtually non existant by the third night. These look like original Hatteras units, either Cruiseair or Marineair. When I pulled the screen off of the air handler under the starboard bunk in the mid stateroom this morning, I got much better air flow although the screen did not look dirty to me. Also, it seemed to be cooling just fine when I did so. Does this make any sense at all?

Steve – thanks so much. My guess too is that it was icing up. The first night, the temps in the stateroom got down to 62 or so. If the unit is to be run fairly constantly, is there a way to prevent it from icing up assuming it is otherwise running properly? I have a big trip coming up this summer and I do not want my kids to be without the air for a month.

JLR said:

Steve – thanks so much. My guess too is that it was icing up. The first night, the temps in the stateroom got down to 62 or so. If the unit is to be run fairly constantly, is there a way to prevent it from icing up assuming it is otherwise running properly? I have a big trip coming up this summer and I do not want my kids to be without the air for a month.

The only way to prevent it is to set the thermostat so that it does not run (cool) in temps below 68 degrees…Do the kids need it colder than that ?

The trick to those manual t-stats is:

Set it to full cooler (clockwise) Then when the cabin temp gets to a point that you feel it's cold enough…Rotate the dial counter clockwise (towards warmer) until you hear a click…Leave it there….The system should maintain the cabin within a few degrees of that temp either way…Meaning it will switch from heat to cool to do so…It's called Automatic Changeover, and works for cool nights & hot days…If the cabin temp does not get more than a couple degrees colder than where you set it, the compressor will remain off till the cabin warms…Where it will come back on in cool mode.

You can test if the T-stat is operational by doing as above…Then with the compressor cycled off…Wrap your hand around the sensing bulb which should be in the return air path (usually right in front of the a/c coil) by warming that bulb the compressor should re-start in cooling…If not…The T-Stat has failed and needs replacement…

Steve~