Break away cable getting red hot where it connects to the car

  • Thread starter Deleted member 27623
  • Start date
D

Deleted member 27623

I have a strange event, where when I travelled at night, and arrived at my destination, I was unable to unclip my break away cable as it was very hot. My first thoughts were the caravan electrics were earthing through the break away cable to the towing vehicle instead of the negative terminal wire on the multi pin. Or maybe the car exhaust has heated it in travel?

Has anyone seen this before?
 
Jun 16, 2020
4,623
1,828
6,935
Visit site
Welcome to the forum aylesage.

What a strange thing to happen. If it was acting as an earth, which I doubt very much, there would be insufficient amps to do that. Easy to check though, remove the breakaway cable and see if the van still operates as it should.

It is not normal for the exhaust to be anywhere near that close.

But you are right to be concerned. That should not be happening. Sorry that I can’t offer any constructive help.

John
 
D

Deleted member 27623

Welcome to the forum aylesage.

What a strange thing to happen. If it was acting as an earth, which I doubt very much, there would be insufficient amps to do that. Easy to check though, remove the breakaway cable and see if the van still operates as it should.

It is not normal for the exhaust to be anywhere near that close.

But you are right to be concerned. That should not be happening. Sorry that I can’t offer any constructive help.

John
Thanks John, the exhaust is approx 15" away from it, so I doubt its that, but i suppose it is possible as the car has a anti particulate filter which it cleans by burning off, this must generate some significant heat. But I still think its more likely to be electrical
 
Jun 20, 2005
17,263
3,486
50,935
Visit site
So your breakaway cable is attached to the caravan braking system and then the cars tow bar. Hard to see what current if any is trying to pass through it?? I’d your cable fully insulated with a plastic sheath?
 
Nov 6, 2005
7,341
2,046
25,935
Visit site
Welcome to the forum aylesage.

What a strange thing to happen. If it was acting as an earth, which I doubt very much, there would be insufficient amps to do that. Easy to check though, remove the breakaway cable and see if the van still operates as it should.

It is not normal for the exhaust to be anywhere near that close.

But you are right to be concerned. That should not be happening. Sorry that I can’t offer any constructive help.

John
I wouldn't dismiss the earthing suggestion so easily - despite being done by a towbar specialist, my previous car had a totally inadequate earthing connection - if the OP's earthing connection is absent, or disconnected, I can believe that it'll try to earth through the breakaway cable.

The tailpipe of modern exhausts don't seem very hot, not even warm in many cases, so I doubt it's that.
 
  • Like
Reactions: Dustydog
D

Deleted member 27623

So your breakaway cable is attached to the caravan braking system and then the cars tow bar. Hard to see what current if any is trying to pass through it?? I’d your cable fully insulated with a plastic sheath?
Hi Dustydog, yes the break away cable is connected to the brakes on the caravan and a fixed point adjacent to the tow bar on the car. The cable itself is insulated but the ends are steel so continuity is for certain between the caravan chassis and the car chassis. Paint and loose connection of the spring clamp, I was thinking could generate heat.
 
Nov 16, 2015
10,394
2,788
40,935
Visit site
Hi Dustydog, yes the break away cable is connected to the brakes on the caravan and a fixed point adjacent to the tow bar on the car. The cable itself is insulated but the ends are steel so continuity is for certain between the caravan chassis and the car chassis. Paint and loose connection of the spring clamp, I was thinking could generate heat.
Very interesting,I am not going to speculate as this needs a real hands on answer..
 

Mel

Mar 17, 2007
5,338
1,280
25,935
Visit site
Fascinating. As I understand it, ( and I may well be wrong) the connection of the brakeaway cable to the caravan brake is a fairly simple mechanical action? What I mean is that if the caravan detaches from the tow ball the cable then yanks on the underside of the handbrake causing the handbrake lever to shoot upward and apply the brake. Hence heat from the caravans brakes wouldn’t transfer to the cable??
If this is the case, I am not technical, but logically there seem to be only 3 potential sources of heat:
  1. electrical through the cars systems earthing or somehow ”shorting” ( don’t think that is the right word) through the brakeaway cable connections
  2. transferred heat from something hot on the car, such as the exhaust or something else that gets hot
  3. friction from the cable connections rubbing on something ( seems unlikely for this to generate as much heat as described.)
Do let us know what you find.
mel
 
  • Like
Reactions: Dustydog
Mar 14, 2005
17,557
3,051
50,935
Visit site
Yes this a very puzzling situation.

I doubt its earthing because that would imply there is a problem with the normal multipin connector, and if that were the case I suspect you would have had some warning lights telling you about thongs like bulb failures. Also there's likely to be an even better earth connection through the tow hitch and ball, so why the breakaway cable is getting hot is a real mystery.

This is a problem where someone needs to actually check things in person.
 
Nov 11, 2009
20,098
6,131
50,935
Visit site
Could the car have been in the process of a DPF regeneration cycle as you approached the site? I had a Skoda diesel that sometimes was part way through a dpf regeneration cycle and the exhaust was hot and engine fans would run flat out.
 
May 15, 2023
137
118
135
Visit site
To establish if it’s electrical, with everything set up as if you were towing but with the breakaway cable disconnected, put an ammeter between the breakaway cable and the vehicle chassis, if the fault is electrical you will see a current flow. If you don’t have an ammeter, touch the breakaway cable to the vehicle chassis and look for a spark.

I would echo previous comments, that if the breakaway cable is providing the earth, and everything thing is ok, I wouldn’t expect the current to be large enough for a chunky bit of metal to get hot.
This could suggest that there is an electrical fault that has caused the original earth to fail because the fault is drawing a high current.

If the initial diagnosis (meter reading) indicates an electrical fault, disconnect the electrics from the car and the caravan battery, whilst you track the fault down, if an electrical fault is causing the breakaway cable to get hot, there could be something in the caravan also getting hot.
 
  • Like
Reactions: Jcloughie
Jun 20, 2005
17,263
3,486
50,935
Visit site
Hi Dustydog, yes the break away cable is connected to the brakes on the caravan and a fixed point adjacent to the tow bar on the car. The cable itself is insulated but the ends are steel so continuity is for certain between the caravan chassis and the car chassis. Paint and loose connection of the spring clamp, I was thinking could generate heat.
Very bizarre as the insulated cable and the bare parts won’t be making a very good connection. A mystery and sorry to say I have no offers of a solution
 
Mar 14, 2005
9,703
602
30,935
lutzschelisch.wix.com
Have you tried all the usual 12v electrical functions in the caravan with the 13 pin plug connected, but without the breakaway cable attached? Maybe that would reveal something.
The breakaway cable itself has a relatively large cross-section, certainly larger than a 2.5mm² lead which is the biggest one in the 13 pin cable, so it would have to carry quite a massive current for it to get hotter than the 13 pin cable.
 
Last edited:
  • Like
Reactions: Dustydog
May 15, 2023
137
118
135
Visit site
To borrow a Sherlock Holmes quote; "When you have eliminated all which is impossible then whatever remains, however improbable, must be the truth."

All objects have a natural frequency or set of frequencies at which they vibrate; "resonate frequency", could it be that the conditions caused the breakaway shackle clip to resonate, in doing so creating heat? sounds a bit far fetched, but in the absence of anything else!

Thinking more about the "electrical fault" theory, as Prof pointed out the towball would provide a better earth..... unless the Al-Ko pads are providing insulation?
 
Nov 6, 2005
7,341
2,046
25,935
Visit site
To borrow a Sherlock Holmes quote; "When you have eliminated all which is impossible then whatever remains, however improbable, must be the truth."

All objects have a natural frequency or set of frequencies at which they vibrate; "resonate frequency", could it be that the conditions caused the breakaway shackle clip to resonate, in doing so creating heat? sounds a bit far fetched, but in the absence of anything else!

Thinking more about the "electrical fault" theory, as Prof pointed out the towball would provide a better earth..... unless the Al-Ko pads are providing insulation?
Or the OP's caravan doesn't have a hitch stabiliser and the towball is greased.
 
Mar 14, 2005
17,557
3,051
50,935
Visit site
Ukdave makes a very valid point about the conductor size, The current needed to heat the cable has to come from somewhere, and the most likely source would be the car, so its almost certain if the heating was cuased be electric current it very likely the 12V connection cable would be at least warm.

I have to say in my mind its highly unlikely to be an electrical fault, as with the level of current needed to heat that mass of metal would almost certainly have blown circuit fuses.

I also think it's unlikely to be resonant heating, but an interesting thought.

But as another out if the box thought, its been rather sunny recently, most of us will know how hot exposed metal can become, and I wonder if the cable has been in direct sunlight?
 
Jun 20, 2005
17,263
3,486
50,935
Visit site
Is the OP using a 13 pin connection or the older 12N &12S?
Another long shot but but if the latter system maybe pin 7 has burnt out channeling the return for the fridge via the breakaway cable??
 
Mar 14, 2005
9,703
602
30,935
lutzschelisch.wix.com
If the breakaway cable were an electrical conductor it would only be intermittent because the shackle or clip between the cable and the towbar anchorage point is loose and wouldn't always ensure a reliable electrical connection. Assuming that it would be carrying an electrical current strong enough to heat up, such a loose connection would be bound to generate sparks while the caravan is being towed. Consequently there would be signs of the metal being burnt locally.
 
Mar 14, 2005
17,557
3,051
50,935
Visit site
This problem is still perplexing me, I have re-read aylesage' posts, and he did say "at night" so my last post about sunlight seems less likely.

There certainly does need to be an elimination process, and as others have suggested, it seems logical to start with the electrical system. From a lifetime of experience, I know that one of the weakest points in electrical systems tend to be connectors, some wear through the number of times the connections are made or disconnected, some build up detritus or corrode with age, some have been incorrectly assembled, so check all the pins, especially the continuity of all the 0v pins to a reliable 0v point in the car.

And similarly do the same for the caravan wiring with reference to a reliable 0v point in the caravan, note, caravan chassis and body work can't be assumed to be a reliable 0v DC or earth point for AC wiring.

In some ways I hope this will show up a problem, but equally I hope it's all good.
 
Jun 20, 2005
17,263
3,486
50,935
Visit site
This problem is still perplexing me, I have re-read aylesage' posts, and he did say "at night" so my last post about sunlight seems less likely.

There certainly does need to be an elimination process, and as others have suggested, it seems logical to start with the electrical system. From a lifetime of experience, I know that one of the weakest points in electrical systems tend to be connectors, some wear through the number of times the connections are made or disconnected, some build up detritus or corrode withage, some have been incorrectly assembled, so check all the pins, especially the continuity of all the 0v pins to a reliable 0v point in the car.

And similarly do the same for the caravan wiring with reference to a reliable 0v point in the caravan, note, caravan chassis and body work can't be assumed to be a reliable 0v DC or earth point for AC wiring

In some ways I hope this will show up a problem, but equally I hope it's all good.
If Aylesage tells us which connection he uses we may be one step closer. Pin 7 burnout has been well explained for decades and solutions offered . Whilst I have experienced Pin 7 failure I’ve never had the breakaway cable heatup.

But as you say this happened at night. Pin 7 would fail at any time so maybe the plot thickens🤔🤔 . I d like to know the makes and models of car and caravan. Was the fridge left running on 12v? How’s the Leisure battery charge post trip?
Intriguing, the Mary Celeste.
 
Mar 14, 2005
17,557
3,051
50,935
Visit site
It is of course impossible to know the cause until its been more thoroughly investigated, but its such an unique report its far more likely to be a one off error and unlikely to be an inherent fault in a specific make or model of car or caravan.

Lets hope Aylesage reports back soon.
 
Sep 26, 2018
620
180
10,935
Visit site
There is one (relatively - and I mean relatively) cheap way to test. Try to find a DC Current Clamp multimeter. These are not too comon, and you have to check that when they say AC/DC that the DC Current is specified, many only do AC current. They are available for under £50 (cheaper than labour rates!).

Set the van up as if to tow with the car attached, open th jaws of the meter and stick them around the breakaway cable, and run the engine. If the meter detects current, that's your problem... Otherwise... It's something else!
 
D

Deleted member 27623

Finally solved it! thanks for all your help. It was dur to an isolated battery to battery charger fitted to the caravan to charge the lithium battery. Because it was an isolated Victron Orion, it was preventing negative ground to the towing vehicle, so it was using the break away cable instead. Fixed now! thanks for all your comments
 
D

Deleted member 27623

so if anyone fits a battery to battery charger, (normally only used for lithium battery charging from the car) don't use an isolated one, or you will use your negative ground to the caravan. Unless of course you link across the negative, so only the positive is isolated
 
  • Like
Reactions: Guzzilazz
Mar 14, 2005
17,557
3,051
50,935
Visit site
Thank you for keeping us informed.

I am amazed at how what you have described has occurred and especially how the route back to the tow vehicle for the DC to DC converters 0V line found the breakaway cable to be a lower resistance than the existing wiring harness.

It's correct practice to ensure that the mains earthing and the negative of the 12V system are hard wired back to the their respective sources. The metalwork of the caravan and its chassis may also be connected to both the mains earth in the consumer unit and the 0V of the 12V system, but becasue there are different parts of the caravans metal some of which may not make a secure reliable electrical contact to its surroundings, it cannot be used as the primary route for mains earthing or the 0V returns.

It sounds as though the DC to DC converter was not installed according to good wiring practice.
 

TRENDING THREADS

Latest posts