Rather than attempt to solve it through deduction, I would concentrate on one refrigerator (the one with the easiest access). Ignore the other one and troubleshoot the one you are focusing on. Power and ground is really all it requires to run on 12vdc. Once you find out what is wrong with that one, the same issue may or may not plague the other.

The temptation is to assume a common problem, but focussing on only common pathologies can prevent a useful diagnosis and make your head explode.

 

Makes a lot sense.

 

Ground Fault tripped?

 

Assuming you are on shore power, check the GFI receptacle in your head? Both AC’s are probably on the same AC circuit.

 

Reading the manual - it appears that the first place to start is to check the boat’s batteries a strong enough to run the refrigerators.

 

Batteries were my first thought--a refrigerator is a HUGE power draw, so low batteries just can't do the job. However, if a fridge is dual power and wired properly, it should bypass the batteries completely when you're on shore power. Have you confirmed what you have and how they're wired? If by some chance a fridge is 12v only--or its AC connection is faulty/has failed--low batteries may one of multiple problems. Check for inline fuses, too, most likely in a very hard to reach place. I doubt we have the same model fridge, but that was an issue for us once. I had to pull the fridge far enough out of its cubby to find it; the fuse holder had become worn and no longer kept a tight connection.

 

Marine refrigerators are designed to cut off when the batteries reach a certain low point of about 11.4v. Are you sure they both are hooked up to 110v? I have one refrigerator that runs only on 12v. I turned the battery charger off one time and accidently forgot to cut it back on before leaving the boat. It pulled batteries to a certain point and then shut down.

Bennett

 

The flickering light is a clue and could lean to the low battery issue suggested or poor connections. That light should just be on or off. If you can't make that work correctly, don't even think the compressor would be able to work.

 

The Dometic refrigerators operates on 12v DC or 24v DC. It uses a rectifier to convert from 100 – 240v to either 12 or 24 v DC. The rectifier senses when it is connected to shore power and rectifier automatically switches from battery to shore power. Since it is both refrigerators not working, I am wondering if they both share the same rectifier that is hidden behind one of the many panels.

 

No there is a black box (power converter) for each one. You need to pull the frige and check the voltages. Assuming that the inside thermostat is on highest cold setting.

 

This is what I think the problem may that the resting charge of my both my battery banks is only 10.8V. It could have been even lower but I started the boat while it was connected to shore power and let the engines run for awhile. It is my understanding that a resting battery charge should be 12.8V and 13.4 when the engine is running.

I purchased new AGM batteries from Sam's Club in January 2019; which makes the batteries 3-years-old now. My memory is telling that 3-4 years is lifespan of a marine battery.

 

This is what I think the problem may that the resting charge of my both my battery banks is only 10.8V. It could have been even lower but I started the boat while it was connected to shore power and let the engines run for awhile. It is my understanding that a resting battery charge should be 12.8V and 13.4 when the engine is running.

I purchased new AGM batteries from Sam's Club in January 2019; which makes the batteries 3-years-old now. My memory is telling that 3-4 years is lifespan of a marine battery.

AGM's should be good after 3 years unless they were abused. regular marine batteries i can see that being an issue

 

Questions: Do all of your other ac appliances operate properly. Air conditioner, hot water heater, stove, microwave, etc. When you turn them on can you see the amperage gauge go higher on the ac side of your electrical panel?

On the 12vdc side, is everything else other than the fridges working properly. Are your lights bright, does your windlass function (properly) or is it struggling, turn stuff on independently and in groups to see if you system handles the load.

 

Check out You Tube presentations on Marine Electrical by Pacific Yacht Systems. Jefe Cote has several seminars he presented on Marine Electrical to include battery behavior, maintenance, upkeep, etc. He is extremely knowledgeable in regards to everything Marine Electrical. You will not be wasting a single minute of your time and you will, as I did, gain a wealth of knowledge. I would say they are the best Marine Electrical presentations I have seen.

 

Argus, from the voltage it certainly sounds like your batteries need a charge or replacement, but that answers the DC side. Have you checked the GFCI receptacle yet for the AC side?

 

Argus, from the voltage it certainly sounds like your batteries need a charge or replacement, but that answers the DC side. Have you checked the GFCI receptacle yet for the AC side?

 

Very true - That is if for some reason unknown to us, some electrical expert (so to speak) changed something up. I once worked on a boat that lost power to the microwave. Owner was not electrically inclined at all. After removing the microwave I found that the receptacle it should have been plugged in to was empty and the microwave wire went through a hole to the left. The dedicated receptacle had no power. So I found the end of the microwave power cord. It had been cut off, spliced with wire nuts to another orange extension cord and was plugged into the outlet in the head. Yes - the GFI. The original outlet black feed wire had come off due to a loose connection which rendered it dead and also a safety issue. Ya just never know. Follow the circuit. Start where you have a full power reading and stop at every switch, plug, junction and test you are getting the same power (no significant voltage or amperage drops) on both sides.

One quick way you can gain some information is to plug your fridges 120vac into a non boat power supply such as a cord directly from an electrical source you know is patent (pier). This will tell you if it is your boats power (or lack of) or if it is the fridges issue. You can also try other appliances (i.e. electric drill, wet dry vac - something that pulls substantial amps) in the plug that your fridge would normally plug in to. This would also help to let you know where your failure might be. Thee are of course meters for all this testing, but you really just need to figure where your problem is - boat or appliance. That at least narrows it down.

For the dc side of this, I am with others on this post, your batteries are toast. Going down to 10.8 volts is non recoverable. It is not enough to power up the fridge compressors and hopefully they didn't burn up continually trying to start up. Aside from your windless, bowthruster (if you have one) and the like appliances, refrigeration is one if not the highest draw on your boats 12vdc system.

 

....Aside from your windless, bowthruster (if you have one) and the like appliances, refrigeration is one if not the highest draw on your boats 12vdc system.

Most fridges don't really draw that much current (5-8A typical, maybe 10-12 on larger ones), but they're nearly a continuous load, which makes them one of the biggest power consumptions on the boat. Spotlights, blowers and electric heads can draw much more current but are used for much less lengths of time.

Compare, for example, a 7.4L motor, which draws HUNDREDS of amps while starting but since it's only ~5 seconds would only use about 2-3AH of capacity each time it starts, or maybe a few times that each day for a total of 5-10AH. Now consider that fridge, which might draw 8A while it's running, but it's running 50% of the time over that same 24 hours and you come up with 96AH.

 

Wow - I am amazed with the knowledge here. I am going to try some simple things that I can know that I can handle. I did check all other electrical accessories, stove, microwave, etc. Everything but the refrigerators works. I do plan to replace the batteries this weekend. I will also check the GFCI in the head also. If I can't figure it out, then it is call to get MarineMax to look at it. I know that need to replace the batteries before I call MarineMax; three years ago they came out to check the alarms that I was getting and charged me $300, just to tell me the alarms were going off due to low voltage and the batteries need to be replaced.

 

Checked the boat this afternoon. Disconnected the batteries and checked each one with a multimeter, each read 12.8 - 12.9. I get 10.8V from the VesselView display on the dash. Not sure what to make of the difference, but it appears that the batteries are okay. The GFCI in the head does not control the refrigerator, it controls other outlets in the cabin but not the refrigerator. I noticed when the battery switch is turned off, the cabin refrigerator's interior light flickers and when I turn the battery switch back on the flickering stops. I pulled the cabin refrigerator out and disconnected it from the 110 outlet. The outlet has power, confirmed by plugging a dehumidifier into the same outlet. Used the multimeter to check DC power to the refrigerator and it read 13.1V. I then removed the AC cord from the refrigerator to check the fuse; fuse is good. I discovered the cabin refrigerator will run on DC if the 110 AC cord is disconnected from where it connects to the refrigerator. When I connected 110 AC cord back in the refrigerator stops running. It does not matter if shore power in connected or not or if the refrigerator circuit breaker is on or off. The refrigerator will run on battery only when if the 110 AC power cord is not connected to the back of the refrigerator. As soon as the 110 AC cord is connected the refrigerator stops running. Don't like giving up, but it now may be time for someone with more technical skills than me to look at it.

 

that’s weird that it quits if the breaker is off.


My guess would of been it was the rectifier that takes the 120v AC that converts it to 12v dc was bad…. But it shouldn’t matter if it’s plugged in if power is shut off to the receptacle. if the 120v receptacle is dead, it should run on the 12v DC….

did you do anything with the cockpit fridge?

 

I didn't want pull out the cockpit refrigerator because it was it is lot harder to get back in. Not sure if I pull it out that I will be able to diagnose and fix anything. I was thinking of connecting the cabin refrigerator to an extension cord connected to a 110v outlet outside of the boat to see if will run then.

I assume it’s a duplex receptacle. Put a digital meter in the receptacle to check the voltage. The while that is lit up (with the voltage reading) have a hair dryer plugged in and turn it on and see what happens to the voltage. It seems like the AC voltage is enough to make the fridge think it has power and not allow it to switch over to DC, but not enough to run the fridge though, that is the only thing I can logically think of as to why when you unplug the AC it runs on DC….

 

Did you ever state exactly which model(s) fridges we're talking about? In one earlier post you reference the CRX but didn't state a model. Do your fridges use the MPS35 rectifier module?

When you wrote "I then removed the AC cord from the refrigerator to check the fuse; fuse is good."... which fuse was that? There should be at least two... and AC and a DC fuse, but there could be a third.

If you are using the MPS35 modules, you could be able to check DC in and out of that module and whether there's DC out if there is the presence of AC in.

 

The cockpit refrigerator is a Dometic CRX-1050 and the cabin refrigerator is a CRX-1080.

Both units use a Danfoss 101N0500`controller. I confirmed that both units will work on battery power if the 110 AC cord is disconnected. When the AC cord in is connected, both units will stop and run again when the AC cord is connected. I also confirmed with a multimeter that both units have 110/120V going to the controller board.

Now I am under the impression that the Danfoss 101N0500 controller itself is bad on both units. Not sure how to test the controller to make sure.

 

 

Diagnostic LED. $10.

https://www.coastalclimatecontrol.c...l.com/shop/online/coastalcoolaids/Diagnostic-LED-Fault-Light-Assembly-p95699140

 

I may have misspoke about the "plug having no power." I will check again when I get back on the boat later this week and post an update.

 

I finally got both refrigerators working. After installing new Danfoss Secop 101N0510 controllers, they both started woking immediately. Installing the controllers was pretty simple. Before installing the new controllers, they both would run on battery power but the 120v AC had to be off. Now they both work as intended. It appears that these controllers are sensitive to power surges.

 

That’s awesome, glad you got them fixed. Thanks for the follow up!

I wonder if @speakrdude could fix those?