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What is wrong with my fridge?

What is wrong with my fridge?

Monday morning the phone runs hot with travellers alike that have a broken down fridge or freezer. whether it be out in the bush or out on the water.

This section applies to 12/24 volt DC Danfoss/Secop BD series compressor fridges. See below for 3 ways fridges.

The first thing that should be done when it is confirmed that your fridge has failed is “Turn it OFF” then you can call your local repairman or technician to discuss the problem. If the fridge has broken a line somewhere and has lost its gas or the cooling fan has failed and the compressor is cooking, the worst thing you can do is continue to run the fridge. It will not magically repair itself and can damage the compressor beyond repair.

The most common problem with a compressor fridge is “LOW VOLTAGE” When testing the battery voltage on your fridge, it must be done at the compressor control module. + & -. The fridge will not even try to start unless it sees 12 volts. The fridge will stop running at 10.7 volts. I know your batteries have 12.9 or 13.5 volts but what voltage does the compressor have when it's running? All travellers should have a voltmeter on board and a basic one can be purchased for under $10.

Voltage drop is a huge problem and many installers are guilty of running insufficient cables to the fridge. 6mm twin core is the bare minimum. If 4mm cable is run for a length of 10 meters, you can expect a voltage drop of around 1.5 to 2 volts, that is a lot of lost power. This also causes the current consumption to go up, the fridge to run longer and hotter draining the batteries even faster. Short cable runs. Thick cables. Less joins. all this will amount to better performance from your fridge. A simple test will tell you if your cables are adequate for the job. Start the fridge. Test the batteries when the fridge is running. Next, test the power cables in the fridge + & – If the batteries are 13.5v and at the fridge 12.5 v, then you have a 1 volt drop.

A great addition to any compressor fridge is a “Fault Indicator Light” In most cases, this will tell the repair tech what is wrong, and make it easier to get the right repairs done. In many cases, I find that out there most fridge techs have very little experience with caravan or boat fridges because they are used to working on domestic fridges, not boat and caravan refrigeration. This can lead to a massive, unnecessary repair bill. Look at the fault code, check with you favourite repairer, tell the fridge repairer what the problem is and get it fixed, simple.

The fault light is easy to fit, it connects to the + for the fan and the for diagnostics. There is a few small exceptions to its accuracy though. when the control module itself fails it can give you a compressor start fault signal. I have listed the fault codes bellow and some other errors that do not show on the fault light.

One Flash= Low voltage. To prevent the batteries from being totally discharged, the compressor will be stopped if the voltage at the terminals on the Module falls below 10.7 volts ( 23.4), & will not re-start until the voltage rises above 11.7v (24.3) volts.

Two Flashes= High voltage. If the voltage exceeds 17v, the Module stops the compressor & switches into 24v mode, but will not attempt to start the compressor until the voltage reaches 24v.

Three Flashes= Compressor non-start. If the compressor does not start, the Module will stop the starting process, &attempt a re-start every 60 seconds.

Four Flashes= Compressor speed too low. If the compressor speed falls below 1500 RPM the Module will stop the compressor.

Five Flashes= Module overheat. If the heat sink on the module exceeds a preset temperature, the compressor will be stopped & will be re-started when normal operating temperatures are resumed.


There are a few things to also be aware of when troubleshooting your Compressor fridge.

  • LED will not signal if thermostat circuit is open. (broken Thermostat)
  • LED will not signal if compressor is running continuously with poor or no cooling. (Broken Fan)
  • LED will not signal if system is low on refrigerant, the compressor will run with little or no refrigerant and still show no LED signal. (lost gas and must be shut down)
  • LED will flash 3 times every 4 seconds if there is way too much refrigerant in system. (or it might be hot)


Brands of fridge that a fault light can be fitted to are anything with a danfoss BD35 or BD50 compressor. Vitrifrigo, Waeco, NovaKool, Isotherm, Evakool are all suitable fridges. DC Fridge sells a 2m after market kit for $35 and it can be fitted by anyone. Many units have them fitted as standard. If you are shy about adding more electronics well this is well worth the trouble and could save you hundreds and hundreds of dollars.

3-Way fridges