Bottom line: life sucks when you don’t have a fridge. They’re incredibly important and painfully expensive to replace. Here are some tips and tests for Dometic RV fridge troubleshooting before hitting the service centre if your fridge is on the fritz.
Don’t you just love when you buy groceries and then they all spoil because your fridge decided to stop working? It’s my favourite. Not. We recently experienced a long, drawn-out fridge repair that was super stressful and held us back from travelling until we got it sorted. After tons of manual-reading and YouTube-watching, we tried about every different test we could find to try to isolate our issue and figure out why our Dometic fridge isn’t cooling. We have a Dometic fridge (RM 2351) and the manual makes troubleshooting quite simple: if your fridge stops cooling, take it to a service centre immediately. How helpful… With the wealth of information available on the internet these days, it’s worth at least giving it a shot before taking it to a professional. Save yourself some cash and maybe even learn something new with our guide to troubleshooting a Dometic RV fridge.
Full disclosure, we are by no means technicians; we’re just a couple of folks that did a ton of research, spoke to experienced professionals, and fixed our $1200 fridge for $7. Also note that this list only applies to absorption fridges. Do yourself a favour and watch a short video to understand how these things work so you can better understand where your issue might lie.
Before getting into the more technical stuff, check the basics. Absorption fridges rely on gravity to function properly so make sure that your fridge is always level. Unscrew the back panel on your fridge’s vent outside of your van/RV, remove the control board cover and check your fuses (side note: apparently it’s quite common for wasps and other insects to build nests in these vents, especially if you’re stationary, so be careful when removing the vent). Ours has two glass fuses, a 3A and a 5A, so be sure to inspect both. Next, check to make sure that your 120v outlet works: when plugged into shore power, plug something else into it (i.e. a string of lights, a cell phone charger, etc.) or get your multimeter and check for a current. Lastly, make sure you have propane and that it is in fact, on. If you’ve solved your problem by this point then rejoice, because your RV fridge troubleshooting days are behind you and you can move on to cool, refrigerated happiness. Also, remember that these things take a while to cool – 6 hours is the recommended time by Dometic to test the temperature. As the technician told us, every time you open the door to the fridge, you lose 1-2 hours of cooling.
CULPRIT: LP GAS (PROPANE)
First, bypass the LP system by putting your fridge on auto while hooked up to shore/AC power and see if it works.
Test the propane by removing the fridge’s vent cover while the fridge is off. Remove the metal cover under the flue tube. Make sure that your fridge is on gas mode, not auto, and have someone turn it on while you listen for the sound of the propane igniting. Once it lights, observe the flame – it should be a nice clean blue flame. If it’s not, there could be an air bubble in your line so bleed the line (turn propane off and light stove until the flame goes out and there’s no more propane in the line before turning the propane back on) and try it again. Next, clean your flue and flue baffle. These are very funny names for very important elements. The flue is essentially the chimney of your fridge and the flue baffle is a twisted metal piece that sits inside the flue tube. These should be cleaned periodically; buildup and dust can affect the performance of your fridge. Also, please don’t be daft and test for propane with an open flame – you’re just asking for it.
CULPRIT: ELECTRIC ELEMENT
First, bypass the 120v system by putting your fridge on gas while disconnected from shore power so it will only use propane and 12v DC power and see if it works.
With the fridge off, switch back to auto and make sure that you’re connected to shore/AC power. Turn it back on and check if the boiler gets warm. If it doesn’t, you may need to replace your electric element or always run on gas mode.
CULPRIT: CONTROL BOARD
Turn your fridge and propane off and disconnect from 12v and 120v power. To test if your control board is shot, which is very common and super easy to replace, you’re going to need to bypass it. Find an appliance you have lying around that no longer works (or get something from the dollar store) because you’re going to need to steal the plug from it. Cut the wire on your dud appliance (leave a foot or two in length) and locate the wires that power the electric heating element, which run from the boiler into the control board. Unplug them from the control board and you’re going to need to hardwire them to the loaner plug that you cut off from your spare appliance. Polarity does not matter so you don’t need to worry about which wires are positive or negative. With your fridge now having a direct plug that doesn’t require the control board or fuses, plug it into your 120v outlet while connected to shore power. Alternatively, you can plug it directly into the shore power source. If it gets cold after a few hours then you’ll need to replace your control board. In theory, if your control board is broken then your fridge should be frozen if you leave it overnight. These run about $100 but are as simple to replace as unplugging your current wires and reconnecting them to the new board. Here’s a link to a video to watch it being done.
CULPRIT: COOLING UNIT
First, check to see if there’s any crusty yellow liquid inside or anywhere on the back of your fridge. It’s possible that ammonia is leaking and therefore, the cooling unit can’t operate properly and needs to be replaced.
Next, since you’ve been such a good reader and attentively watched the video on how absorption fridges work, you know that the cooling unit is powered by a series of chemical state changes and the only way these state changes can occur is if the tubes are clear for the ammonia to flow through. It’s possible that there is a blockage, which is either past the point of no return or can be “burped” by turning the fridge upside down. Sounds odd but this is an old school trick that can work shockingly well and costs no money – AKA the perfect solution. You’ll need to make sure your propane and AC/DC power is off and then disconnect your fridge completely. Take a photo of the back of the fridge first so you can see where all your connections go and then label and take photos of each piece as you unhook them so you can easily hook them back up in reverse order. Remove the fridge from its housing inside of your RV and carefully turn it on its side and then on its head and listen for the sounds of liquids flowing. I’ve read a lot of mixed information about how long you should leave it upside down and there doesn’t seem to be a definite answer so we rotated it 2-3 times consecutively and then left it upside down (and level) for about 3 hours. We could hear the liquids moving through the tubes as we turned it so we knew that was a good sign. After 3 hours, turn it right side up and leave it to sit overnight before turning it on. It’s important to leave it turned off and sitting upright for longer than 3 hours to let everything settle again. Carefully hook everything back up, turn on your power and propane and turn the fridge on. Test the temperature in 6 hours. Cooling units can be replaced at home but are a little messier than upgrading other elements. If you can find a replacement at a decent price then go for it but be aware that these are usually $500+.
Most RV fridges are equipped with a clip on the back fins that allows you to control the temperature slightly. The sensor inside that thermostat is called a thermistor. In a nutshell, as the temperature drops, the thermistor increases resistance and sends more ohms through to the control board. Once it reaches a certain temperature (usually about 1°C/34°F), it’ll reach an ohm rating (usually between 7-10k Ω for Dometic fridges) that sends a signal for the fridge to turn off. It won’t come back on until the temperature rises to a point where the ohm rating is below the shut-off level and requires cooling again. Anyway, if the thermistor is broken then either A) your fridge will cool slightly then stop because it thinks it’s cold, or B) your fridge will always be frozen because it thinks it’s warm. To test your thermistor, unhook it from the control board (follow the wire coming out of the back of your fridge beside the drainage tube) and turn your fridge on. Within 6 hours, it should be cold and if left overnight, it should technically be frozen, depending on what your ambient temperature is. You can replace the thermistor by buying the kit from Dometic, buying a temperature control dial with a built-in thermistor or buying a generic thermistor from an electronics store and connecting the wires to those of your broken thermistor in order to reuse the plug specific to your control board. This ended up being our culprit, so we bought an epoxy coated thermistor that came with a tiny resistor and wired that into our existing plug. You must make sure that it is an NTC thermistor (negative temperature coefficient) so that the resistance increases as the temperature drops. The ohm rating is key here, ours is 10k Ω, which is a pretty standard one. Standard, but not suitable for this purpose (see below).
*JAN 2019 UPDATE:
Although the 10k thermistor we swapped in got our fridge working again, now that it’s winter and we need far less cooling power, we’ve noticed that the fridge never shuts off. As mentioned above, the thermistor should send a resistance of 7-10k when the fridge reaches temp telling it to turn off. Turns out the 10k resistor isn’t our answer because it doesn’t send that ohm rating until it reaches +25°C, AKA not a temperature you ever want your fridge to be. With some research, we’ve found that you’d actually want to buy a thermistor with a 2.8k rating instead of 10k (data sheet for further reading here and product link here). Send us a message if you find yourself needing to replace your thermistor with one of these bead ones and need some direction on how to do so – you’ll need to solder it onto your existing wire and coat it in an epoxy or liquid electrical tape to assure it’s waterproof.
All in all, RV fridges can be pretty intimidating but are really not as scary as you may think. It’s worth taking some time to troubleshoot your Dometic RV fridge on your own before taking it in for repair or replacing it altogether. Just make sure to be careful when dealing with all electric and gas connections and to give your fridge enough time to cool down. They are said to take 12 hours to fully reach temperature but factors like the outside temperature and humidity can slow this down and leave your fridge working overtime. The ambient temperature in an RV parked in the desert is going to have a huge effect on the performance of the fridge in comparison to a fridge sitting in a 10°C/50°F room. Be patient, be careful and keep that fridge level!