Thetford Caravan 12v electrics with new car

[Grahammy]

Recently bought a new Mazda CX60 diesel mild hybrid. Recommended by a number of magazines as a good tow car. It tows really well. But: when in transit with car hooked up the fridge won't work. I've had the caravan electrics tested. All OK. The mazda 13 pin electrics checks out OK, without being connected. We've followed the usual routine for cooling the fridge before any trip. My mazda guy is at a loss as to what the issue is. Has any one else had this problem or do you have any suggestions. Ps obviously I realise the fridge should only work when the engine is running, but even then it won't work. Attached is the model number etc.
Graham

 

[borderbilly]

Loads of posts on here on that subject. It is a marmite topic, some do bother to run fridge when towing, others dont. Me, i dont bother, not worth the hassle, i wait till im on site and hook up with EHU. Each to there own.

 

[Hutch]

The forum has had many people,stating their fridges don't work with modern cars.
Answers relate to "Smart Alternators".
I don't know enough myself, I think others will help.

 

[Grahammy]

The forum has had many people,stating their fridges don't work with modern cars.
Answers relate to "Smart Alternators".
I don't know enough myself, I think others will help.

Thanks Hutch, much as I thought. But are we to just accept this as insurmountable I wonder? As borderbilly says we may just have to give up on the 12v option. Which will be a shame.
Ciao.

 

[otherclive]

Thanks Hutch, much as I thought. But are we to just accept this as insurmountable I wonder? As borderbilly says we may just have to give up on the 12v option. Which will be a shame.
Ciao.

Might be worth using the Forum search using Smart Alternators, and you don't need to input a members name to say who said what. But as BB and Hutch say it is very car model dependent. Some have technical get arounds, others ways to load the alternator so it does put out the voltage, some rewire as the cars wiring isn't adequate and introduces voltage drops, others pre cool the fridge on house mains or gas, then pack it with cold/frozen stuff for the journey. One member reaching Spain and everything still edible/cool. I was in the later camp even though my fridge would work en route. No one has accepted it as 'insurmountable' and there are some very experienced and knowledge members on the Forum. It is a fact of modern technology mismatch between car and caravan. Some get it sorted others don't or have work arounds.

 

[RogerL]

Try the car with engine running and headlights + heated rear window on - with caravan connected, if the fridge circuit then works it is a smart alternator issue.

If this is the case, ask whoever fitted the towbar wiring to fit an ignition-sourced relay rather than a voltage sensitive relay - but even then you may need a voltage booster in the caravan fridge circuit.

 

[birdman101]

With engine running check voltage with meter on pins 10 and 11. If you haven’t got 14+ volts there, by the time it reaches the fridge with voltage drop ,Thetford fridges need 13+ volts for the fridge relay for the Element to kit in..When I had Hyundai I had to run a thicker cable to prevent voltage drop by the time voltage was at the Thetford fridge.

 

[Hutch]

With engine running check voltage with meter on pins 10 and 11. If you haven’t got 14+ volts there, by the time it reaches the fridge with voltage drop ,Thetford fridges need 13+ volts for the fridge relay for the Element to kit in..When I had Hyundai I had to run a thicker cable to prevent voltage drop by the time voltage was at the Thetford fridge.

As an Add on to Birdman. On my Santa Fe, the fitter of the towbar had wired all the earth's into the earth wing into the harness. The fridge and ATC would not work I had to wire separate earth's from the cars socket pins direct to the cars chassis. To get the fridge and ATC to work.

 

[Kevin M]

My van works fine on my 2025 Ford Ranger so not all vehicles have the same issues it seems.
As long as out fridge is cool, we can travel 7-8 hours with no issues of the fridge not being cool on arrival at our destination.

 

[Woodentop]

One thought: has the computer been told that the car is now wired for towing? On VAG vehicles for instance, when the caravan is hitched up, engine running and reverse selected the reversing picture on the Infotainment unit changes from an outline vehicle to one with an A-frame attached. Don't know about Mazda but its worth checking.

 

[IanB1485]

People often check if +12V is present , but forget the 0V .At the back of the fridge(lower vent gives access) there is a 4/6 way connector , there will be two thicker wires , possibly red )+12V volts and white (0V, or as some call batt negative), when hooked up to the car with the engine running check you have 12 volts between these two wires . Please note that modern fridges will cut power to the 12V heater element and flash up an error if the voltage drops below a certain threshold, can't remember what value it is off hand.





9

 

[garry campion]

Recently bought a new Mazda CX60 diesel mild hybrid. Recommended by a number of magazines as a good tow car. It tows really well. But: when in transit with car hooked up the fridge won't work. I've had the caravan electrics tested. All OK. The mazda 13 pin electrics checks out OK, without being connected. We've followed the usual routine for cooling the fridge before any trip. My mazda guy is at a loss as to what the issue is. Has any one else had this problem or do you have any suggestions. Ps obviously I realise the fridge should only work when the engine is running, but even then it won't work. Attached is the model number etc.
Graham

I'm sure you have already tried this, but the last two cars I have had the fridge won't come until the engine is running, sorry to tell you how to "suck eggs" but thought it was worth a try

 

[ProfJohnL]

I'm sure you have already tried this, but the last two cars I have had the fridge won't come until the engine is running, sorry to tell you how to "suck eggs" but thought it was worth a try

He Knows that. The OP covered this point in his penultimate sentence , which you copied into your post!

We don't know if the car has successfully powered a previous fridge?

We haven't been told for certain that the car has had the auxiliary circuits wired in - Many "standard" towing looms do not have the fridge and battery charge circuits included. It is wise to specifically state in your order documentation that these circuits must be included. See Birdman and Hutches posts #7&8

As Woodentop points out in #10 some cars need to be reprogrammed to accommodate towing and the Aux circuits.