Sub Zero freezer temp inside salon

My sub zero freezer temperature is only going down to 10 degrees. Do these freezers sometimes need an additional Freon charge. Its been like that the past two years (maybe more) but thought it should be closer to zero. This freezer works off 120v power no saltwater cooling. The boat or generator has not been running when temp is checked.

The SZ freezer is one unit about the size of the two drawers. My SZ refrigerator has two drawers. I cleaned the coils underneath the unit this morning and not seeing any temp drop. The seal seems to be good but not sure how to check that. The fan your speaking of is it up top close to the thermostat control inside the unit. Not sure if the fan is working as I don't hear it. If the fan was not working would that make a difference in the temperature?

Just went out and removed enough to see that the fan is not working as the unit had already started icing up. Not sure how to replace the fan as not much room to work in. Where do you recommend ordering parts for Sub Zero? The seal looks fine and there is a slight suction when opening the door. So may have two issues could need more Freon and fan motor definitely will need to be replaced.

I removed the fan tonight and checked it with 120v power. It worked so something else is not sending it power when its suppose too. Trying to find a wiring diagram. Could be the fan door switch. I'm guessing.

Anyone know off hand what Freon the SZ model 249FF uses. The unit is a 2005.

Yes got the evaporator fan working but evaporator coil area is frosting up and freezer temp starts climbing. I've ordered a defrost timer and defrost terminator from southerncoastalparts out of Jax that should be here on Monday. Hope this will fix the issue. Talked to a couple of appliance repair companies and that was their suggestion. You are correct there is no schrader valve its a closed system. Will post the results.

Based on a few your feedback & some online videos I decided to replace the defrost timer and defrost terminator which I ordered from southerncoastalparts.com. Lucky guess on my part but they fixed the problem. Freezer is on #3 and 0 degrees. First time I ever remember it being this cold.

Well so much for that short lived success. The past two days the freezer temperature has been 18-20 degrees. I ordered a new thermostat control and replaced it thinking it could be the culprit but it wasn't. Going to find service technician tomorrow.

If I could find one in this area that would be great. Only one and he's tied up through the month of May. Subzero recommended I find an appliance repair person and they would talk him through the diagnosis since no marine sub zero person available.