Tech- Inside a Dometic NDA1402
Last week, I attended a course on the “New Generation” of Dometic refrigerators. The 3 models we looked at are the RM3762/3962, fairly conventional top/bottom 2 door models with new control circuitry, including constant LED readouts of the temperature in the fresh food cabinet, the RM1350, a large 4 door model, with cold water through the door, the same temperature readouts as the RM3762, a “tag line” (ignition switch) hookup which both locks out LP operation for refueling purposes, and activates an automatic door lock, and the most interesting model (at least to me 
)- the NDA1402- a side by side model with the first true auto defrost in an RV refrigerator.
I thought it might be interesting to look “under the hood” to see how this model works….
The NDA1402 is a side by side model, with a small twist in layout- as you can see, the freezer portion is somewhat larger than normal, which- added to the vacuum insulation (meaning thin walls with good insulation) gives a fairly large food storage volume.
But… the most interesting part- both from a use and service point of view- is the automatic defrost.
The first thing you have to do when you first start up this model is to set the clock… yes, this refrigerator has a clock. “Why ?” you may ask- pretty simple. The clock lets the refrigerator go in to defrost mode at 1 AM every day, when the doors are likely to be closed, and the refrigerator will have plenty of time to recover from the added heat of defrosting.
“Added heat?”…. Yes, this model has 4- 12 volt heaters in it to do the actual defrosting, and to keep the drain tubes unplugged.
Here’s a picture of the fresh food heater, which is installed behind the cooling fins in the compartment. Notice there is also a fan to circulate air. There are defrost heaters and fans in both the freezer and fresh food compartments.
To control all of this, the unit uses 4 thermisters (temperature sensors)- 2 in the freezer, 2 in the fresh food compartment. 1 thermister in each is attached to the cooling coils, the other reads the air temperature.
In operation the defrost cycle starts at 1 A.M. First, the cooling unit is turned on for 1 hour to pull the temperature down (it will stop before freezing the fresh food, though).
Next, the unit is shut off for 10 minutes, to allow the cooling unit to “relax”, or equalize the pressures in the system.
The freezer heating element is energized next, along with the freezer drain tube heater. The defrost heater stays on until the freezer plate temperature reaches 41° (or 75 minutes, whichever is first). The fan in the freezer is shut off during this procedure (we just want to defrost the plate, not heat up the freezer), but the freezer fan is run for short periods to throw any water off of the blower.
After the freezer defrost cycle has completed, the cooling unit is started again, and the fresh food defrost actually takes place while the unit is cooling. Because of the slow recovery of absorbtion type refrigerators, the timing lets the cooling unit get a head start on recovery. The fresh food defrost cycle is until the fins reach 41°, or 20 minutes. The fan is also shut off for this cycle, and the drain tube heaters stay running for 30 minutes after the cycle is complete.
The defrost cycle can be started manually, and if it is started manually, and if the freezer door is held open, it goes in to the “drying” mode- which is used for storage. In the drying mode, both heaters are run for 3 hours. At the end of this cycle, the unit shuts completely off. This helps eliminate mold and rust from forming.
A couple more features this model has that I thought I would mention- it has temperature readouts for both the freezer and fresh food compartment, and it has ice and water through the door. The ice maker and ice and water dispenser are standard household models, and run on 120 volts, so while it will make ice running on LP gas, it will not eject or dispense ice unless 120 volt power is available- though the units now use 2 separate 120 volt cords, so the ice maker function can easily be run off an inverter.
It was interesting to me to see where the “state of the art” in RV refrigeration is headed, and it will be interesting to see if some of this technology gets in to the standard 2 door “top freezer” models.
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JUST HAD TO ORDER A DOMETIC, LAST ONE I PURCHASED
ABOUT 7 YEARS AGO FOR ABOUT 1,000 IS NOW 1700. WHY
CAN’T THEY LAST LONGER, ESPECIALLY NOT USING MUCH BUT
ALWAYS PLUGGED IN.
I WAS THINKING NORCOLD BUT DIMENSIONS A LITTLE DIFFERENT SO STUCK WITH THIS ONE THAT FITS IN THE HOLE.
J. THORNTON
Chris, I was wondering if Norcold is pretty much same as Dometic? Did you have to pull the fin in order to see behind? Is that where the fan blower is? I thought absorption does not have a fan like home refrigerator.
Hi Rickie,
This models is different than pretty much anything out there- it has a lot of home type features (like the fan), and the fins do remove from the inside, which they did in the 1970’s, but not other modern RV refrigerator does.
–Chris
Might be off topic but please help!I have a Dometic RM2652 refrig. with the auto on feature.Unit works fine,all fuses and connections good.My question is,How do you know when the unit is working on AC?The gas is always lit when shore power is on.Is this normal?
Thanks,
Ed
Hi Ed,
The gas should not be running when 120 volt power is supplied to the refrigerator. The most common cause of these not switching to 120 volt is a popped GFCI outlet in the rig, which is usually in the bathroom (though they are putting them in more and more locations).
You basically want to test the outlet the refrigerator is plugged in to and make sure it has power.
If it does have power there is a fuse under the cover for the circuit board (2 actually- a 3 amp fuse for 12 volt, and a 5 amp fuse for the 120 volt).
What a dummy I am!!Ipulled both fuses and visually checked them.They looked great.I then spent a couple more hours checking things out.No good, gas was still running the frig.Pulled fuses again,got my meter out.The 5 amp fuse was bad!!Moral to the story,always,always do a continuety check.So learn from this dummy.
Ed
Hi Ed,
I should have suggested that- it’s a fairly common problem with refrigerator fuses. What happens is the fuse holder gets a bit loose with a touch of corrosion, and the end cap of the fuse heats up, and the fuse element just comes unsoldered.
Glad you got it working!
–Chris
I’m getting a “Call” error 13 on mine (NDA 1402), drain tube heaters.
Do you have a picture of those? I’d love to know where to find the little buggers. This error 13 is intermittent and can probably be fixed by removing, cleaning and reinstalling them.
Thanks in advance!
Chris — I have the NDA1402 in a 07, Monaco Camelot — The Frig is in the road side slide-out, so the top vent is in the sidewall — My problem is, the ice maker does not dump very often, if at all — The freezer gets to about 10 & sometimes lower, depending on weather — The fresh food compartment in the high 30`s — I replaced the ice maker, but same results — I added a fan at the bottom vent to assist the 2 stock fans — I believe that the tray is not getting cold enough, but can`t find any way to adjust that temp — HELP —- Bill Willard
Chris, I have a Dometic RM1350 in a new DRV Select Suites and when I remove a container from the running water coming from the door, the water continues to run for 3 seconds or so making a mess. We’ve heard from other owners in the club that they have the same problem. A local rvia repairman called Dometic and they told us to hold the glass under until the water stops! They didn’t get the idea at all. At some point you have to remove the glass and then the continuation of water running happens. Have you heard of this problem on the RM1350? Also, how do you get the smell and taste from the ice maker in the freezer? We have santized the fresh water tank 3 times and dumped numerous trays of ice and still a taste and smell! HELP!!!! We think this new unit is definitely not an “upgrade”. Any input would be greatly appreciated. Thank you, Roger
I’m also getting a “Call” error 13 on my (NDA 1402), drain tube heaters.
The same problem as Thanks In Advnace described. I had the heater tube wiring replaced last year. Got another error 13 this year. After a few days on the road the code reset and is now ok. Is there someway I can reset the error?, or is this an intermittent problem in the new model.
Chris, dometic rm2852 check light on in ac auto mode any tips on this would be great .took the 5th wheel to dealer replaced the lower board and also the electrode. took the trailer home pluged in .the check light was on again the refrigerator works fine in gas mode. seems to be cold in ac mode too but the check light is always on (921 1461-28) thank you Don
I also have an error reading CALL 13 on my Dometic NDA 1402, where can I find a schematic of the electrical and the construction of this model refridgerator?
Is this a promblem with the drain heater inherit with this model?
Thanks Glenn
Hi Chris, I have a Dometic NDA1402 in an rv also. The problem I have is this: During normal outside temps, up to about 80F, the fridge works fine. On a recent trip the tempurature outside was around 100 degrees F and the temp inside the fridge climbed to about 59 degrees F. I ran the diagnostice and all was fine. I checked the vents from the roof down, the gas burner and electric element are working. I tried removing the outside vent cover with no improvement. Friends I travelled with had no problems with the fridges in their RV’s, one with a Dometic and one with a Norcold. Any ideas would be appreciated.
Thanks, Dick
I also have a problem with the NDA 1402 running warm in warm outside temps. I just spoke with a local repair shop and he indicated that the 1402 was not designed to be installed in a slide. Of course mine is so there is no roof vent to allow the warm air to escape. It does have the outside cold air kit with two brushless motor Rodale fans (similar to an oversize computer case fans). His solution was to maybe install additional fans to help circulate the warm air out of the frig outside compartment and run the additional fans only in warm weather above 80 degrees F. Think I will give this a try since all of my diagnostic codes indicate everything is working properly.
I have NDA 1402 model. I cannot set anything….clock or temperature. Holding the set down for 5 seconds or pressing the auto set does not work. Frustrating… Any suggestions. The “tech” in my area does not seem to know. Many thanks.
Hi Chris,
I too have an NDA1402 with error code 13. I have seen others mention this problem but have not seen your comments regarding a solution.
Can you offer any advice on what I can do to correct the problem?
Thanks,
Don
> This is the two door NDA1402 refigerator with ice and water dispenser on the door.
>
> Our 50a supply receptacle to the motorhome had a problem where the neutral conductor failed open. This condition burned up our central vac, which the wife was using at the time, and our bedroom clock.
>
> Once power was restored, I noticed the ice and water dispenser on the door were inoperable. Also the light did not work. Luckily the fridge and ice maker are still working. I removed the outside cover and searched for WHATEVER. I noticed that the 5A fuse was blown on the dispensor power switch (a control board). I replaced the fuse, it held, but, the dispenser is still inoperable.
>
> I’m asking if anyone has had a similar problem and what I can do myself short of taking the coach to an authorized Dometic Service Center. The fridge is on warranty until Jan 2010 for parts and labor, but, if there is an easy fix, I’d prefer to do the repair myself.
>
> Gary Graus
> 07 Scepter 42 PDQ
I also have an error code 13 on a model NDA 1402 I have been trying to find out what is the correct part to correct, (book says the drain tube heater is bad) I found a number 3850676010 but the product code on the parts manual is not correct.. My product code is 921 1484-15 Any help is appreciated.
Chris
I have a Dometic RM 1350 in Keystone Everest. The refrigerator is in a slide out.
The problem I am having is that the freezer stays cold but the refrigerator stays in the upper 40’s. I was told by a tech to add a 12 volt fan to the top vent, but that does not seem to do the trick.
Any advice?
my dometic model no. 1402 will not autodefrost and the clock is set correct, can you please help.
DOMETIC NDA 1402 NOT MAKING ICE ALL THE TIME OR ONLY MAKES A LITTLE MOLD THEROSTAT ?
what is the normal operating temp for a nda 1402 mine runs at -4 to 5 when set on 3 fridge is at 38-40
Hi Chris,
Dealer went under, code 13 on NDA1402, have heater 3851411011 and would like to replace. any advise on the easiest procedure?
Thanks
Clark
How do you reply to post?
I have a dometic 1402 and the ice maker blows the 5A fuse. I tried a 10 fuse and it blew too. It was working fine until I changed from crushed ice to cubes and thats when it blew. Hasn’t worked since can you give some ideas? Is it the switch? The auger motor works so I’m assuming that the motor isn’t the problem.
Still have no answers to my refrigerator problem. Has anyone had that same problem with their 2008 1402 dometic refrigerator blowing fuses. Sure could use some help as to what to look for.
Hi Pat,
That’s really not an easy one to diagnose remotely, as I don’t have a lot of experience with this model, but I will say the ice maker and dispenser are both standard Frigidaire parts, and are not RV specific.
I also have a 2008 NDA 1402 Dometic Refridgerator , and my question is , can this unit be modified not to defrost every 24 hours ? Maybe once a week would be enough . This thing is a bear on energy consumption , especially if you do a lot of dry camping ! With 4 fans , 2 heating elements , and then re-cooling to get it back to operating temps again , it seems like it never stops working . I live in Arizona and have to keep the temp setting at # 5 just to keep things cool . My solar panels are enough to keep up with it during the day , but when the sun goes down , this unit uses a lot of battery and propane . I’ d appreciate any comments or suggestions .
Thanks….
Dometic NDA 1402 Freezer Door Switch Problem
The 1402 works as it should except that the freezer temperature varies between 6 and 20 degrees for no reason.
What I know: I have never heard the freezer fan run in normal mode. In service mode it runs OK. All other service modes are OK except the freezer door is always open. When closing the freezer door I can hear a relay click in the back. The same click occurs when the refrigerator is running in normal mode and the freezer door is closed.
It certainly appears that the fan is not running as it should to keep the freezer temperature low. Any suggestions on what is causing the problem?