Code 6 (code 12 on older pre-R3G fridges) is one of the most common complaints we get from dealers on our fridges. This is something that happens mainly on caravans but can happen on motorhomes too.
The issue is caused by a low supply voltage from the tow car and is often mistaken for a fault with the fridge, with a dealer usually assuming it's a rear power board problem. This however is rarely the case and in most probability the 12V supply voltage is low. This can be caused by various different things, such as:
- Dirty or corroded tow socket
- Bad connections on the supply wiring between the source (car/starter battery) and the back of the fridge
- Excessively long supply wiring (sometimes seen with horseboxes and large RVs
- Cable with too small a cross-sectional area
This fault can also be caused by the "smart" electronics on some tow vehicles. Some of these vehicles disable the alternator when the engine is running to save fuel. Unfortunately this has an effect of lowering the supply voltage to the fridge, which can cause the fridge to go into fault. Similar issues can also occur when the vehicle is fitted with start/stop technology.
To check whether the fault is actually a supply issue, we need to check the supply voltage to the fridge, specifically at the Red and White "High Current" terminals on the back. These terminals power the 12V heating element in the fridge. Please be aware that we need to check the "on-load" voltage when the fridge is switched on and drawing current and not the "resting" voltage.
The video below shows what we would expect to see in a good installation. We have a power supply providing a steady 13.8V to the fridge, as a typical alternator would provide. As we can see, the voltage at the back of the fridge drops slightly when the fridge is powered on. This is due to the resistance in the wiring and it's this voltage figure we are interested in. Our fridges will accept an "on-load" voltage of somewhere between 10.5 and 15V so the installation below would be considered normal.
In the video below, I have replicated a scenario which will cause a fridge to give a fault code 6. There is now a large amount of cable between the power supply and the back of the fridge. This causes a large amount of resistance which causes the "on-load" supply voltage to drop too low, triggering the code 6 fault. Note that when the fridge is switched off, the supply voltage appears to be healthy but when the fridge is switched on and draws current, the voltage drops significantly. This shows why the fridge must be powered up and running to check the voltage and confirm a wiring issue.
As you can see, it's important that when a dealer claims a fridge is at fault, we need to be sure they have checked the voltage under load. It's quite common for them to turn the fridge off, go back outside and measure the voltage. As the fridge is now switched off, the voltage will appear to be good which would make the dealer believe the fridge is at fault when this is likely not the case.
It's also worth noting that some installations an inadequate supply will cause the fridge to click on and off over and over again. Again, we would need to check the on-load voltage when this is happening. If it is a supply issue, we would expect to see the voltage rising and falling with the clicking, sometimes down to zero.
Lastly, it is worth mentioning that this fault is quite common on installations where a new fridge has been fitted in place of a failed unit. There are 2 reasons for this:
Firstly, the heating elements in modern fridges are more powerful that they were and draw more current. The factory-installed wiring loom in an older van would have been designed to power the original fridge but may not be up to powering the replacement. In this case, the only fix is to run a new wiring loom in the van in a thicker cable to cope with the extra current.
The second reason is, a lot of older vans had "dumb" fridges fitted which did not have on-board diagnostics. It's not uncommon for there to be a bad connection somewhere in the wiring loom but as the original fridge was not able to report this as a fault, it was not noticed until the new fridge was fitted. What normally happens in these cases is the customer will complain, stating something along the lines of "it was working before" or "it's only started since this new fridge was fitted" etc. In these cases we would need to check the on-load voltage as above to check whether it's an issue with the fridge or an issue with the vehicle.
Finally, and touching back on vehicles with "smart" electronics. Depending on the towbar installation, it's sometimes necessary to create a load on the vehicle's electrical system to fool the electronics into keeping the alternator running and the supply voltage up. The majority of decent towbar installations would allow the vehicle to sense the load from the fridge, but some (surprisingly some manufacturer-fitted bars) do not so a load would need to be created. This would be done by switching on something relatively power-hungry such as the headlights or rear window heater etc.
Thanks
Rich