Dometic fridge ok on LP, not on AC

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Sandgrubber

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Nov 11, 2012
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Gainesville, FL
My Dometic RM 3663 goes directly to LP in AUTO mode and will not operate on shore power.  The fuses are all ok.  As I understand it, this is most likely a failure of the electric heating element.  Questions: 1. Could this be something other than the 120 V heater ?  2. I'm pretty mechanical as old ladies go, but I'm still something of a nervous nelly.  Is replacing the 120 heating element easy?  3.  I can't find any local rv mechanics.  If I'm not up to a DIY job, how do I find someone to do it for me?  P.s.  I've found the installation and user manual but can't find a technical manual.
 

waroland

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Feb 28, 2009
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Mount Juliet, TN
What kind of RV? The frig needs 12 volts DC and 120 volts AC to run on AC. It only needs 12 Volts to run on propane. If it goes immediately to propane you may have a breaker popped not a fuse.
 

s2kskibum

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Feb 19, 2010
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Mine does the same - I'll follow this thread, but I am useless for help - sorry. I am guessing the heating element is easy to replace, these are not complicated machines!
 

Sandgrubber

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My fridge seems out to prove me wrong.  Last night it kept going from LP to CHECK.  Then in the early am it switched to AC and stayed there for a few hours.  Now it's back to LP.
I'm staying at a funky fish camp campground whose idea of providing power is stringing a long extension cord from the office/house.  I'm beginning to suspect that the fridge is fine ....but doesn't know how to operate with a dirty power supply.
 

Greg H.

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Apr 20, 2012
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Maryland
I had the same problem with my 3663... the problem is not necessarily the element.  I recommend that you take a look at the service manual: http://gasrefrigeration.net/dom_techdata/2707_2811sm.pdf; it lists six possible causes for that type of failure. 

I followed the troubleshooting process provided in the manual for my system and found that the lower circuit board was not functioning, my heating element was fine.  I purchased a replacement circuit board for about $100 (http://www.pplmotorhomes.com/parts/rv-refrigerators/dometic-refrigerator-dinosaur.htm) and that resolved my issue. 

If you're not up to DIY, I'd find a reputable RV service center and have them diagnose and resolve the issue.
 

pixurit

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May 16, 2010
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If you suspect dirty power, or perhaps a voltage drop because of the "long extension cord from the office/house", I'd eliminate that possibility first.

Recently I had a problem with dirty 12V power to my Dometic RM 3862.  The symptoms were similar but not identical to yours.  When on shore power the indicator lights would switch from AC to GAS every couple of seconds (function set on AUTO).  If I manually switched from AUTO to GAS the burner would fire and then shut down after a couple of seconds, wait a few minutes and then try again, over and over. I finally realised that this problem only occurred when the kitchen fluorescent light was on.  I checked the 12V fuses and found that the light and fridge were on the same circuit.  My trouble shooting started with checking and cleaning all wire connections in the circuit ... no change.  The fluorescent light worked the same as ever but I did notice a slight discoloration in the finish around where the ballast mounted.  I replaced the still working fluorescent light fixture with a new one.  That was a tough decision for a frugal guy who believes in finding and repairing problems, not throwing new parts at them until they finally go away.  The new fixture did solve the problem.  I figure that even though the light worked fine, the failing ballast was "dirtying" the 12V power on the circuit and confusing the Dometic's circuit board.

If you do get to the point where you suspect that the Dometic circuit board is the problem, you can remove it and have a local RV dealer's service department do a bench test before trying a new one.
 

Alfa38User

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Oct 4, 2007
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Are you aware of the 3 fuses in the back of the Fridge??? On most Dometic models, by looking through the access panel, you will spot a small black box with wires going in and out. Remove the box cover (1 screw) and check glass tube fuses found underneath by using a meter (not just looking at them). Replace the blown 5A fuse (F7 if my memory is good).

Whenever this fuse is blown, the fridge will always go straight to LP as this fuse is supplying the 120 Volts AC to the electric heater.

Norcold's also have these fuses in a box in the back.
 

Lou Schneider

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I'd eliminate the funky incoming AC as a possibility first.  You can have some amazingly dirty power and not know it - all of your lights are 12 volts and the batteries and converter do a remarkable job of taming power problems before they get to your lights.

It may just be that the AC voltage is falling out of the refrigerator's operating specs, and when it does it switches over to gas mode until the voltage comes back up.

There's nothing wrong with locking it in Gas mode as long as you're at that campsite.  Refrigerators use a surprisingly small amount of LP gas.
 

Gary RV_Wizard

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Your refrigerator is actually plugged into a wall outlet, usually located behind the fridge and accessible from the outside access door. Next time the fridge won't run on 120vac, unplug the fridge and plug a lamp or something into the same outlet and see if that works. Better yet, use a VOM or outlet tester to check the outlet.

It sure sounds like your power source is flaky, either intermittent or perhaps low voltage.
 

Sandgrubber

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Nov 11, 2012
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Gainesville, FL
Thanks, everyone , for input.
Update:  I've moved away from the site with funky power supply to a private site that needed a bit of work, but has dedicated power, accessible without extension cords.  Last night the site wasn't very level, and I could only get LP.  After some tractor work I now have a level site, and, bingo, the AUTO select went right to AC.  Conclusion: the system is working fine, it's just particular about voltage and leveling.
Now on to figuring out why the water heter is shutting off before the water gets hot.  I may have this rig shipshape by next summer!
 

Molaker

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Springfield, Mo.
Sandgrubber said:
Now on to figuring out why the water heter is shutting off before the water gets hot.
Are you sure the water in the tank is not hot?  You may have the winterizing by-pass vavle(s) in the wrong position.
 

FocusTom

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Mar 18, 2017
Posts
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I found this topic while trying to figure out why my Dometic fridge suddenly stopped auto switching to ac. After checking the fuses in the back of the unit and checking the breaker box with no luck I pressed the reset button on the gfci outlet...and the problem was resolved. Hope this helps someone.
 

voyaginator

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Aug 25, 2015
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FocusTom said:
I found this topic while trying to figure out why my Dometic fridge suddenly stopped auto switching to ac. After checking the fuses in I pressed the reset button on the gfci outlet...and the problem was resolved. Hope this helps someone.

Thank you for posting this, we recently purchased a Dometic https://goo.gl/UTRKgN and got a bit concerned about DC to AC switch when back home  :( Anyway, so far so good we like this portable cooler/freezer    :)
 

Trivet

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Oct 27, 2012
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We just had the same thing happen on our Norcold.  Removed the circuit board and part of it was all charred, so we replaced it and that fixed the problem.

The circuit board may still be bad even if it isn't charred, but if it is, you can be pretty sure it should be replaced.
 

NIBGA

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Oct 26, 2017
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My 1998 Dometic 110v heating element shorted in 2017 taking out the glass fuse. I ordered a new element from Amazon.

When I tried to replace the element, it was frozen to the tube that it was in. I broke the l shaped top off. Grump!!! Once that happens there is no way to get the element out short of pulling the fridge and drilling out the tube. 

I had replaced the cooling coils with an OEM version a few years before by JC Refrigeration in Shipshewana IN . Their cooling coils have TWO tubes for the 110v heater. The new heater went there, replaced the fuse and bingo, fridge again works on 110v & gas.

Why did I replace the cooling coils? A friend of mine with the same age fridge had the coils leak and had to buy a new fridge. When that happened I decided mine wouldn't be far behind and replaced the coils. The Dometic NDR1062 is the largest interior double door ever made for an RV. The replacement is 2 cu. Ft smaller as my friend found out.
 

Gary RV_Wizard

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The Dometic NDR1062 is the largest interior double door ever made for an RV.

Two-door, as in top and bottom?  The NDR1402 is a side by side double door, and the Norcold 1200/1210 is a side by side double, and those are 14 cu ft and 12 cu ft respectively. There are other 12-14 cu ft models too.
 

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