Caravan Fridge

[birdman101]

The 12 v display control panel must be working or the gas or mains voltage would not of worked. But unless they applied a voltage to the fridge via the caravan 13 pin plug of 13 +volts,the fridge element cannot work on 12 volt setting, as the fridge relay for the 12 v element will not operate.

 

[Martin_E]

They usually use a test box I mentioned this in post #8 some have amp meters on so you can see what is being drawn. I think workshops use a test box that is mains powered a lot of mobile workshops often have a battery power test box.

Like https://www.ebay.co.uk/itm/15649602...586&gbraid=0AAAAAC5ena0_A9H46w61TppfP3n4LUWZz

 

[ProfJohnL]

Thank you, no tow car is the same, it’s just the service people said when the van was serviced that the 12v fridge wasn’t working. I’ve not yet tried it when connected to the car. All the other electrics work fine through the tow bar.

I find it hard to justify the dealer quoting you £70 to investigate.

With the right standard workshop gear and a well informed technician it would take about 2mins to establish if the fridge does not work in the 12V aux wiring. And 5 mins to follow the wiring to the vicinity of the fridge checking for problem connections.

In my opinion based on the comparative simplicity of the fridges 12V circuitry the charge a charge of £20 would be more realistic, and it should be refundable if the fridge or the caravan wiring is found to be at faulty caused by manufacturing.

Assuming the wiring is correct and the fridge does not work, the fault lies with the installation of the fridge or the fridge itself, both of which are manufacturing errors and should be dealt with under either manufacturers warranty or the your statutory rights established by the Consumer Rights Act 2015 by the retailer.

You will probably find the caravan manufacturer defers a warranty claim on the fridge to the Fridge manufacturer.

 

[birdman101]

The test boxes only test road lighting as I have watched dealer check. Does not check fridge on 12 volt for towing

 

[ProfJohnL]

The test boxes only test road lighting as I have watched dealer check. Does not check fridge on 12 volt for towing

That will depend on the design of the test box. I'm surprised if they don't have a battery charge and fridge tester, they certainly should if its a caravan workshop!

 

[birdman101]

Tests wiring but does not put enough voltage on to operate the fridge as the tow car does

 

[Martin_E]

The test boxes only test road lighting as I have watched dealer check. Does not check fridge on 12 volt for towing

You are wrong there, I have seen one being used, it showed the amp draw when the fridge circuit was being used via the towing electrics

 

[Martin_E]

That will depend on the design of the test box. I'm surprised if they don't have a battery charge and fridge tester, they certainly should if its a caravan workshop!

The two I have seen do have both.

 

[Martin_E]

Tests wiring but does not put enough voltage on to operate the fridge as the tow car does

They definitely can (the ones I have seen, anyway)
as an example https://tow-tester.com/product/powered-remote-control-caravan-electrical-tester/

 

[IanB1485]

Most caravans use wire with a conductor size of 1.5mm CSA this has a resistance of 0.012 Ohms per metre With a current of 10A that means it will cause a voltage drop of approx 120mV per meter length.

Err the fridge heater wires in a caravan aren't 1.5mm2 , they are 2.5mm2 which has a resistance of 0.00798 Ohms per metre, so the voltage drop will only be 66% of the value you calculated. It's still a factor though , the other one being the 12V heater wattage compared with 240V heater wattage is lower. On a tall RML8230 fridge/freezer its 170W compared with 190W for the 240V heater. On smaller under bench fridges like the RMS8551 its closer 12V= 120W, and 240V = 125W ,small differences, but they all add up.

I wonder how they went about checking the 12v supply from the car battery to the fridge? Not quite the same, but the fridge requires 12v to the control panel for the fridge to work on 240 or gas. however that 12v comes from the caravan battery? Confusing isn't it.

I have a free standing battery and control unit I can plug in to the 13 pin socket and run the fridge for about a minute on 12V , just to check the element and control system is OK. To run it for longer I have recently purchased a 280A.hr Li PO4 battery. Also I have an extension 12 core lead so I can plug it into my car if pushed, Motorhomes are so much easier -just start the engine!

 

[Buckman]

I have a free standing battery and control unit I can plug in to the 13 pin socket and run the fridge for about a minute on 12V , just to check the element and control system is OK. To run it for longer I have recently purchased a 280A.hr Li PO4 battery. Also I have an extension 12 core lead so I can plug it into my car if pushed, Motorhomes are so much easier -just start the engine!

Excuse my ignorance. How would that work as surely it would be the same as if using the caravan 12v battery especially if the car has a Smart alternator? Would you connect the 12v battery up at source i.e. the plug connector for the car? Surely if you are doing that you would need to run the fridge for at least an hour or more to test it the load the fridge would be drawing as the fridge will be "warm" and be drawing a lot more amp before the thermostat kicks in. As said a numpty regarding caravan electrics etc.

 

[ProfJohnL]

Err the fridge heater wires in a caravan aren't 1.5mm2 , they are 2.5mm2 which has a resistance of 0.00798 Ohms per metre, so the voltage drop will only be 66% of the value you calculated. It's still a factor though , the other one being the 12V heater wattage compared with 240V heater wattage is lower. On a tall RML8230 fridge/freezer its 170W compared with 190W for the 240V heater. On smaller under bench fridges like the RMS8551 its closer 12V= 120W, and 240V = 125W ,small differences, but they all add up.

Standrads have changed since I last had to deal with car/caravan connector, some 25 years ago, when cables seemed to 1.5 csa as defined by the NCC 's electical compliance notes. A 1.5mm csa is acrually rated to 20 A but its resistance might cause enough volts drop at 10.8 to produce a problem.

Even though standards may have changed there are still reports which could be volt drop related.

 

[birdman101]

How does 12 volt actuate the fridge voltage sensitive relay to power the element when the small Orange wire on Thetford fridges, is only getting 12 volt feed. The relay wire needs a higher voltage as it gets when the Engine running and Alternator putting out up to 14.2 volts.