Dometic RMDX21 Fridge – Mods and Repairs

In our 2017 Essential Exceed Caravan we a standard Dometic RMDX21 3 way manual switching fridge/freezer. Very happy with it, though it has had a few issues over the last year, all so far solvable!

Beeping for no reason

Some of the parks we have stayed at the fridge will start beeping for no apparent reason. Obviously check the door is closed to start.

However after a while we realised it’s a power problem. The RMDx21 appears to be quite sensitive to mains voltage and the beeping in our case was from low mains voltage. Unfortunately it doesn’t tell you this anywhere, even the manual.

At the last site it was doing this it was while the aircon or even just the toaster was running, other sites it would just do it randomly all day.

The quick and simple fix was to switch over to gas until we moved to the next site.

Slow running Drain:

Over flowing drain tank:

Freezer door jammed:

When running on gas, the condensation that builds up around the door locks can then freeze and jam the locks in place. This is why whenever you arrive at site you should disengage the locks, especially on the freezer door. On 240v power this is not an issue as the frame heater keeps the ice melted. On our particular fridge there may be a little more play in the hinge than others, because when the lock jammed up I was able to lift the latch end of the door about 3mm which was enough to lift it over the latch!

If you can not do this, you can use a hairdryer (if you have one) on the side of the door where the latch is to melt the ice. You can also turn on the Cabinet Warmer (read the instructions!) however this uses a fair amount of battery so you don’t want to run it too long when not on power.

Door Latch not holding

We arrived at site today to find the contents of one shelf all over the floor… That shelf had the glass jars like beetroot, tomato salsa, mustard, pickles etc. So it took about an hour to clean up the mess of food and glass, that thanks to the rather rough South Australia roads had ended up covering most of the floor.

Mess cleaned, now to work out why. Turns out the latch was not latching, felt like a spring was broken. First pic I am holding the latch down, second I have let it go and you can see its lifted up.

So we pulled it off and pulled it apart. Pretty easy really, peel the white sticker off the latch, undo the two screws and take it apart.

Once removed, on the back is the catch holding it together, prying gently with a small screwdriver to pop it apart, and yep, spring in two pieces. I tried to stretch the larger part of the broken spring, but as soon as I lifted the latch the spring was compressed back to being too short. Pulled apart a pen and used the spring out of that. Opened up one end to fit on the latch the stretched it a bit to wrap around in there. Seems to be working well for now, might try to find a proper fitting replacement if it starts to loosen again.

When refitting the latch, just make sure the lever goes under the rod coming down from the button. It’s not spring loaded, so will have dropped down below the latch. You need to insert it at an angle to get it under that rod, the when in position screw it in and refit the white cover.

Power issues:

Some of you may remember last year I accidentally turned off the main battery battery switch momentarily, but when it switched back on the fridge did not power up. Long story short – 24 hours later with the fuse removed it finally turned back on and I put tape over the switch to never turn it off again! I was thanking my lucky stars thinking the main control board was borderline terminal.

Anyway, fast forward 6 months and the fridge is now turning off randomly while driving and running on the car battery. The car power only runs the element in the fridge, the main computer is powered from the van batteries. So I check all wiring assuming a bad connection, and yes the main power leads (push on spade type connectors) are not very firm at all. So a quick squeeze with the pliers to increase the pressure and job fixed or so I thought. Next drive upon arrival the fridge was off again. It got to the point that closing the door firmly or moving stuff around in the fridge to hard would shut it down.

I played with the wiring and fiddled for ages with it turning off all the time but just not able to work out exactly what wire was causing it. Then when looking at the wiring closely (couldn’t find a wiring diagram) I realised the thermal circuit breaker on the flue is actually inline with the incoming power to the fridge control board, so if it failed, no power to the fridge at all. Close inspection found it was in a bad way with the terminals rusted and the rivets holding the terminals rusted as well, resulting in the terminals being quite loose. As a temporary fix I have pulled the connectors towards each other under pressure with some Velcro to stop them moving until I can buy a new one (currently in Lichfield National Park – not too many refrigeration repair centres around here!). UPDATE: Tried everywhere and ended up back at my favourites Everything Caravans… A new one is on its way.

UPDATE: replacement arrived, this is the old one after removal, you can see why power dropped out over bumps!

Stopping the bugs!

Our previous van’s fridge stopped working on gas at one stage so I had to take it down to get looked at. Turned out the lovely QLD mud wasps had decided to make a nest inside the flue system blocking the airflow. Time and $$ later I decided to put fly screen mesh over the vent to prevent this. Just normal fly screen, not midge screen as I didn’t want to reduce the airflow too much. I placed the fly screen over the back then dobs of hot glue to hold it in place. Working well. I did not do the same on the top vent as ours is a roof mounted upper vent and the screw holes had been filled with silicone so was too hard to remove in the time I had. Working on the premise that the wasps are too lazy to fly all the way down the bottom to make a nest!

Lost the vent cover!

Well not us, but on our travels over the last year I have seen plenty that have lost the standard Dometic outside fridge vent cover. Ours is missing half of one of the lugs that hold the front in place and with it fitted over the ribbed aluminium it was always half popping off. Was thinking of a few options then saw what Bob had done and copied (Travelling Oz Our Way). Simply remove a middle screw from each end of the vent frame, drill a matching hole in the vent cover, refit the cover, put in the screw. Very simple and that vent cover is not going anywhere.

Auto shut off on car battery:

Our power feed from the car for the fridge is run directly to the car battery via a 50 amp auto resetting circuit breaker. I separated this from the 12pin trailer connector so I could unplug it when we stop for lunch somewhere to avoid running the car battery flat (the fridge draws around 13 to 14 amps continuously). Since I keep forgetting to unplug and was worried I was going to be stuck somewhere, I decided the easy way out was to install a VSR or Voltage Sensitive Relay. I picked up a 50amp KickAss branded one and installed it behind the fridge, plenty of room. Simply cut the main 12v fed from the car, put a ring connector on the cut ends and bolt them on to the VSR. A small black wire off to the negative connection and works like a charm. Once it detects over 13.2v for more than 15 seconds it turns on, when it detects less than 12.8v for more than 15 seconds it turns off.

Defrosting:

The fridge seems to defrost itself fairly well when on 240v, but the freezer ices up and needs cleaning out once every 2 to 3 months depending on the humidity. Once the freezer ices up too much it stops keeping things cool. A quick job assuming you have a hairdryer on hand. Empty the freezer, remove the shelf, place a plastic tray under the fins and a towel to soak up the water, hairdryer on low fan high heat and aim at the first fin at anywhere you can see the aluminium. If you cant see any, pick the part with the least ice. Once that’s been in the heat for around 10 seconds the sheet of ice will simply pull towards you and off the fin. Repeat for all fins, stopping to clean up the ice and water as you go along. Takes no more than about 10 minutes and the ice cream hasn’t even had a chance to start melting!

That’s it for this post, any other great ideas you have for these fridges let me know and I will add them in!