Trying to fix our deck freezer

Archimedes came with a giant deck freezer on the flybridge when we purchased her. Since that time, the deck freezer has never worked. In fact, it could not have ever worked. Even for the folks that put it on the boat originally. The basic problem can be defined as this — it doesn’t get cold. With the thermostat set to its coldest setting, the freezer will get down to the mid 30’s. That’s makes it a serviceable refrigerator, but this is supposed to be a freezer. It also uses 5-6 amps all the time while the compressor is running.

From time to time I’ve tried to get it to work right, but without success. I’ve rewired the power (more on that later). We had the guts replaced (in hindsight, we probably didn’t need to). And it still doesn’t get cold. The compressor runs all the time and there is lots of frost buildup inside.

We took it to a reputable repair facility. They told us they added refrigerant and it worked right for them. But it still won’t get cold for us.

As it turns out, it took a fair bit of internet sleuthing to locate a likely solution, but I did find it. I think. Maybe. Of course, I could be completely wrong. And I am making a big assumption. I am assuming it can work properly as a freezer.


The solution is two parts.

First, a bit about the deck freezer. As I said earlier, it came with the boat. It’s up on the aft flybridge. The freezer compartment is around 4.5 cubic feet. The compressor and other guts are in a compartment on the right. We don’t know where it came from (perhaps Boat Electric) and we don’t know how old it is. It looks like it would be a handy thing to have if we can get it to work correctly.


The guts of the freezer are in the compartment on the right. The compressor is a Secop BD35. The rest is a cooling fan, wiring, and some tubing to connect it to the plate in the freezer section. That’s about all there is to it. Pretty simple.


As you can see in the photos, there is considerable frost build up on the coiled tubing. Everything I can find tells me this is due to too much refrigerant. This is also the reason it runs all the time and doesn’t get cold. Or at least that’s what I have been able to glean from the interwebs.


Because of the frost on the tubing, and the heat of the compressor, it drips water from the drain in the compressor compartment all the time too. An added bonus.

So the freezer runs all the time, doesn’t get cold enough to freeze, consumes too much power, and drips water onto the deck. That’s why the freezer is in the garage.

We brought the freezer home and plugged it in to a twelve volt power supply I bought on Ebay.


I made this gizmo a while ago to monitor power usage on the boat. The watt meter was about $15 on Amazon. Connect it between the power and the load and it shows voltage in, watts used, and amp draw. Useful information.


From what I have read, the right amount of refrigerant is very small. The capacity is measured in grams. Unfortunately, since most installations are different, there is no way (at least for me) to determine exactly what the right amount is for our freezer.

I bought some refrigerant and this valve gizmo to connect it up to the compressor. Automotive refrigerant is the wrong stuff. Don’t use that. The valves won’t connect to the compressor and the oil is the wrong kind.

Once I got it all up and running, I used the tried and true method of trial and error. I let refrigerant out of the system slowly. I shut off the power and let a small amount of refrigerant out. The valve is a standard Schrader valve like you would find on a bicycle tire. I opened it for one or two seconds, powered it back up, waited two hours or so and checked the temperature inside. With the thermostat set at 5, slightly below half way, I started at about 30 degrees and after two days of this, I was down to about 14 degrees. The compressor runs 15 minutes on and an hour or so off. And power consumption is down. 2.5-3 amps when the compressor starts, then slowly decreases until the compressor shuts off. Much better.

As noted in an earlier photo, releasing some of the refrigerant also eliminated the frost buildup on the coiled tubing and the resulting accumulation of excess water in the compressor compartment. My unscientific goal was to get it so that there was barely frost where the tubing goes into the freezer compartment and the cooling plate was lightly frosted evenly across its surface.

Using this approach, I was able to get the freezer down to eight degrees. As is typical for me, I wasn’t happy to stop there. I let just a bit too much refrigerant out and the temperature started to climb. So it was time to add a bit more refrigerant and start the process over. After more trial and error, I was able to get it down to 9.5 degrees. Time to stop.

The freezer now seems to be working well. At least in the garage. I figure if it can maintain 9-10 degrees in the garage, I can keep it 20 degrees or so on the boat when it is outside and the weather is warmer. That should be adequate for our purposes.

On to the second part of the solution, and another reason why I know the freezer never worked right. Power. According to the Secop manual, and other sources I was able to find, the compressor requires a very good power source. The manual recommends connecting directly to the batteries. The original wiring was 14 gauge. I had changed it to 12 gauge in the past because I didn’t know what I was doing. That happens quite often. According to the manual, based on the length of the run, I need 8 gauge wire.

This is where the project is now. When we get the boat back from Canada, and the weather improves a bit (or at least dries out for a day or two) I will take the freezer back to the boat and pull new 8 gauge wire. Then I’ll cross my fingers, power it up, and see what happens.

Here are a couple helpful links to the knowledge I needed.

There is more information about marine refrigeration there, these are just the two main pages I referenced.

To sum up, before the compressor ran all the time consuming 5-6 amps continuously, would not cool below 30 degrees, and dripped water onto the deck all the time. Afterward, it runs for 15 minutes or so every hour, and uses 2.5 amps, cools to 9 degrees, and doesn’t drip water on the deck. Counter-intuitivly, the solution was to decrease the amount of refrigerant in the system.

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