Caravan wiring problem

Submitted: Thursday, Apr 25, 2013 at 11:54
ThreadID: 101873 Views:3533 Replies:7 FollowUps:10
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Hi all, We picked up our new Newlands Onyx last June and love it. We have used it about six times now and I have been impressed with the build quality and haven't had any problems at all until our last weekend away, a couple of weeks ago. We had only been on the road about half an hour ( with our headlights on ) when I heard a click under the dash and the dash lights went out. The clearance lights on the caravan were also out and my mate following behind cofirmed the tail lights out as well. Everything else was working fine. I unplugged the van, replaced tail light fuse, everything fine. Replace plug, lights on and out she goes again. Replace fuse again, left lights off and finished our journey to the caravan park. While there I had a look at the plug to see if anything was amiss, all looked OK. There were a few electricians in our mob so it didn't take long before a multimeter came out. There was a reading of about 5 ohms across the Tail and Earth terminals of the caravan plug. I have done a bit of wiring on cars, boats and motorbikes over the years but I am not and expert by any means. I have checked what visible wiring I can but cannot find the short. Has anyone any ideas or have had a similar problem? Have rung dealer, manufacturer can't look at it until early June. Any help will be appreciated.
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Reply By: Notso - Thursday, Apr 25, 2013 at 12:18

Thursday, Apr 25, 2013 at 12:18
Have you pulled out each globe one at a time to see if the OHM reading changes? I have seen in the past an internal short in the globe has occurred.
AnswerID: 509741

Follow Up By: On the Run - Thursday, Apr 25, 2013 at 12:57

Thursday, Apr 25, 2013 at 12:57
follow the wiring and see if anything has rubbed while travelling
FollowupID: 787734

Reply By: Member - John and Val - Thursday, Apr 25, 2013 at 13:25

Thursday, Apr 25, 2013 at 13:25

Assuming the taillight bulbs are incandescents (not LEDs), I'd expect to see about 2 to 5 ohms at the plug. That's roughly the cold resistance of all the bulbs in parallel. Suggest remove all bulbs and I think you'll find the 5 ohms goes away. (ie goes to infinity.) It would be worth leaving the meter connected, with no bulbs and shake the wiring around to see if you can create the fault. Worth having a look especially at the connections on the back of the plug - if a wire comes loose in there, and is free to touch a neighbour, it can create an intermittent connection/short that will disappear under Murphy's Law when looked at then reappear when maximally inconvenient.



J and V
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AnswerID: 509746

Follow Up By: Member - Geoff P (VIC) - Thursday, Apr 25, 2013 at 13:55

Thursday, Apr 25, 2013 at 13:55
Thanks for your quick replys. Sorry, I should have mentioned that all lights are LED and there are heaps of them! Two at the top of the front, three down each side below window height and four on the rear ( two at the top and the tail lights ). They are difficult to remove from the van because they are screwed and stuck on with self adhesive backing. I managed to get one of the clearance lights off with some carefull prying and face pulling. I would love to have the wiring diagram to get an idea just where the wires run. Sorry about heading you all down the wrong track. I'm trying to get out of taking it to the factory, it is on the other side of Melbourne, about 90 k's each way.
FollowupID: 787740

Reply By: Dust-Devil - Thursday, Apr 25, 2013 at 16:53

Thursday, Apr 25, 2013 at 16:53

The first thing I would 'attack' is both the socket and plug of the car/caravan connection as there is usually 7 different cables in each one with a zillion little copper strands in each insulated cable. every now and again one of these little strands gets loose and cause a problem or two.

Easiest way to check, is to get one of your mates who has a matching plug setup to yourself, to bring his vehicle around and plug it into your van. If all is okay then you know its in your Tow Vehicle. If not and it blows his fuse as well, then its in your van somewhere from and including the plug and the rest of the van.

Happy hunting.

AnswerID: 509760

Follow Up By: Member - Geoff P (VIC) - Thursday, Apr 25, 2013 at 19:05

Thursday, Apr 25, 2013 at 19:05
Thanks DD, I was so focused on the caravan I never thought it could be the car. My son has got a Cruiser so it would be interesting to plug that in. Worth a try. Thanks.
FollowupID: 787761

Reply By: awill4x4 - Thursday, Apr 25, 2013 at 17:15

Thursday, Apr 25, 2013 at 17:15
Geoff, what tow vehicle are you using?
I'd say it's not necessarily a van wiring issue.
Sometimes the sheer number of lights overwhelm the vehicle fuse and it only shows up when you are driving at night or when your lights were on as yours obviously were.
I know on Pajero's which I have, the hazard light fuse is a common issue (10amps) once the fuse is changed to 15 amps the problems no longer occur.
Perhaps change the vehicle fuse that blew and put in one 5 amps heavier and see if the problem re occurs when driving with all your lights on.
Regards Andrew.
AnswerID: 509761

Follow Up By: Member - Geoff P (VIC) - Thursday, Apr 25, 2013 at 19:19

Thursday, Apr 25, 2013 at 19:19
Hi Andrew, I will give this a try. I have got a 2002 4.8 lt Patrol which I, would have thought, would have reasonable wiring to handle extra loads. I am at the stage where anything is possible so everything has to be checked. As DD said, it could be in my car wiring, so will check bigger fuse first ( easier to do! ) and if no go, then get my son to bring his car around. I have dismantled the plug and checked resistance again and it is unchanged.
FollowupID: 787762

Reply By: Ross M - Thursday, Apr 25, 2013 at 21:13

Thursday, Apr 25, 2013 at 21:13
Geoff P
Because caravan makers just "cause" holes for light wiring instead of creating holes properly there is a high likelyhood one of the holes has a jagged edge and the wiring which supplies that light has been moving and rubbed through the thin plastic insulation, hence the sudden shorts sometimes.
First you have to make sure it isn't just a loading and heat issue which is blowing the fuses.

Since your lights are LED's the loading shouldn't be too much. Maybe fuse size.

If you solder wires onto the ears of a blown fuse and connect the ends to a 50w globe approx, it should run all the tail/side lights and if suddenly the big globe comes on brightly it will indicate a sudden short is happening. These are hard to detect and requires most of the lights to be removed and checked to find the fault which the maker "built in" as a feature for you to enjoy finding. They don't like looking for them. Once you check the integrity of the light fitting you will know they are good, which can't be said for anyone else doing it, that is trust.

Ross M
AnswerID: 509785

Follow Up By: Member - Geoff P (VIC) - Thursday, Apr 25, 2013 at 22:16

Thursday, Apr 25, 2013 at 22:16
Hi Ross, I have taken one of the side clearance lights off and it was covered in plenty of silicone where the wires go through the cladding. The wires from the fitting had an outer sheath on them as well. The short has to be somewhere and I agree with you that it is most likely this. I also agree that if you do it yourself, you know it is right. The warranty has nearly run out so I suppose that will remove one worry if I stuff around with it myself. How do I remove the stop/tail lights to check them? No visible means of support. I like the idea of the fuse tester thingy.
FollowupID: 787789

Follow Up By: Ross M - Thursday, Apr 25, 2013 at 22:52

Thursday, Apr 25, 2013 at 22:52
I haven't seen your rear lights, but i would imagine if they don't have obvious holding/fastening screws they may clip in like many side and running lights do.
You probably have checked for stray wire strands in the plug and also if the cable has been squashed between something.
The fuse/globe unit on a length of cable allows driving with the problem and saves fuse after fuse.
No danger with the use although the lights may be a bit dimmer than normal while the test fuse/globe unit is in place.
You should be able to see when it happens ie over a bump or turning and that gives some ability to trace the fault.

If over bumps, look for wiring which is loose and floppy where it goes into chassis holes etc. Maybe just worn through.

I once saw brake wiring which had been looped through the coil spring of a suspension. Professionally installed of course and still working at that stage.

Best of luck
Ross M
FollowupID: 787793

Reply By: Member - J&R - Friday, Apr 26, 2013 at 10:25

Friday, Apr 26, 2013 at 10:25
You mention your 'new' caravan.
Why are you playing with the problem?
You may do more damage or partially void your warranty.

The problem will be up inside the skin where the loom travels through struts and reinforcement/braces. In all probability, it will need the skin removed in areas where the harness runs to locate the problem.

As you have mentioned, you have checked the obvious places. Now give it back and push them. Shorts inside caravans are terribly hard to trace. And time consuming.
AnswerID: 509821

Follow Up By: Member - Geoff P (VIC) - Friday, Apr 26, 2013 at 18:13

Friday, Apr 26, 2013 at 18:13
Hi J&R, I connected the caravan plug to the car today to do further tests and the darn thing is working OK again. I am convinced it is either the plug wiring or a short in the wires leading up to the plug, the caravan hasn't moved and they are the only things I have touched. I know you are right about it being their problem but if it is something simple that I can fix I would rather do that than loose two days work and tow the caravan all over Melbourne. If I can't find anything I may not have the option and will have to take it to them. Thank you everyone for your replies, you have been very helpful. Geoff
FollowupID: 787855

Follow Up By: Dust-Devil - Friday, Apr 26, 2013 at 19:14

Friday, Apr 26, 2013 at 19:14

I was helping my brother in a an Alice Springs caran park a couple of years ago when this guy he new asked if I would have a look at the wiring on an old caravan he had just bought that had an intermittent fault.

Long story cut extremely short - in total frustration I cut the plug off approx a foot from the plug itself, purchased a new plug (aluminium Hella) and wired it in.

Bingo! He hasn't a problem since.

My brother and I virtually destroyed the old plug in an attempt to identify the fault, with no luck at all.

Another thought for you to ponder on.

FollowupID: 787858

Follow Up By: Member - Geoff P (VIC) - Friday, Apr 26, 2013 at 22:07

Friday, Apr 26, 2013 at 22:07
Hi DD, This whole thing has been fustrating for me because I'm pretty sure the problem is in this area, BUT it could be anywhere in the van. Even though the plug is near new, I will change it and see if this helps ( won't hurt to have a spare anyway ). I will be having a very close look at all the wires that come out of the plug and disappear into the "A" frame. Thanks for the point to ponder.
FollowupID: 787874

Reply By: KenInPerth - Saturday, Apr 27, 2013 at 12:25

Saturday, Apr 27, 2013 at 12:25

Late reply but just another bit of input.

An old trick (with a bit of fiddling) is to wire a 12V globe in series with the wire for the lights that are causing the problem (I assume it might be brown wire on pin 7 for a 7 pin pug). You could use any old lamp housing you might have - one terminal to the plug and other to the wire disappearing into the van such that it is in "series" with the wire.

You may then be able to wander around the van (with someone watching the test globe) and if (as you push / pull / prod / bang things the light comes on or shows signs of lighting up) then you would at least perhaps locate the area of the problem.

As others have said, the problem could be anywhere and that is the real nasty bit - including a faulty LED globe (or lamp assembly) - at least with the test globe in series you can push and poke and tap all the things you can get to without blowing fuses (the test globe will light up instead).

AnswerID: 509888

Follow Up By: Member - Geoff P (VIC) - Saturday, Apr 27, 2013 at 18:06

Saturday, Apr 27, 2013 at 18:06
Hi Ken,
It looks like I will have to do a test like the one you suggested ( Ross had a similar set up, but at the fuse ). I have inspected the lead and the 7 pin plug and they seem fine. Everthing still working OK, shaking and banging lights and anything else to do with it. No blown fuse yet. I will have to take the caravan for a run over some rough roads with a globe set up in the tail light circuit and see what happens. Thanks for your input Ken.
FollowupID: 787919

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