New member with marker light problems

[jseaman]

We have a Burstner 500 TS, our first caravan and we're about to take it out on it's first trip. I fitted a tow bar to my car this weekend and tried it out, all is fine except for the marker lights. It's a sinlge 7 pin arrangement and I was finding that only one marker light was visible but none of the others.

If I use a power supply to fire ground and 12V into the pin on the 7 pin connector (removing the car from the equation completely) it still does the same thing. Upon further investigation I'm getting 2-3V at a couple of the lights so they are not getting enough power to light up properly.

I've tried putting +12V on the front marker light and that lights up the 2 front ones perfectly. Similarly if I put +12V on the side marker lights on either side, all 3 (the two side amber and the rear white/red) light up just fine.

So my question is, are there any fuses or wire links I should know about? I imagined it would be a straight wire run from the 7 pin connector to the lights but have only followed through to the point that the lighting connector enters the floor at the front of the van and appears to go under the door way.

Any thoughts would be welcomed!

James

 

[ProfJohnL]

Hello James,
First of all the caravan is not of British origin, so some of its wiring may differ from common practice here in the UK.

But the telling comment you make where you can only get "2-3V at a couple of the lights" suggests you may have corrosion on some connection that produces a high resistance with voltage drops.

On UK caravans all light fittings must have a wired 0V connection so it does not rely on the chassis. these often corrode or rust and may need some TLC to clean them up and make a good connection. I suggest you open all the light clusters, and clean the bulb contacts and spade connections. If there is no wired 0V return I suggest you add some wiring to make sure of a good complete circuit.

 

[jseaman]

Thanks, I couldn't figure out how a bad connection would cause it when putting 12V into a light directly lit them all. I figured it must be wiring between the lights. That said, I wanted to follow your advise and cleaned up every light and fitting on the van. Before I started to clean them up, the two front lights came on brighter than before, almost looking correct actually. I checked the others and they magically started working too. They haven't wavered since, I've wriggled every wire I can find and nothing to indicate a bad connection. Very odd indeed.

I cleared everything up, I found one earth screw which wasn't tight but otherwise fine. Note that there wasn't the typical white build up you identify with bad connections anywhere. How do people wire the external lights, they appear to go into a fibreglass hole of doom all around the vehicle?!

Following the clean up, no change to the front two lights. I can see about 10V on the pins but can't deliver any current to the bulbs. I opened up the 7 pin connector and re-made every connection to no avail. At the moment I have both side markers and the rear white/red light plus number plate on both sides. There must be something wrong though for them to come and go like this but I don't think there's a fuse and can't see most of the wiring. I just have the two front lights to sort now but that can wait for daylight!

 

[ProfJohnL]

Hello James,

Can I point you to a useful page about the UK approved road lighting schemes.

http://uisalumnisage.org/enclosed-trailer-wiring-diagram/enclosed-trailer-wiring-diagram-5/
I must point out that continental practice and colours may vary. though the outcome should be the same. In particular you should note the side markers on each side are fed from different pins in the connector.

Because you are still reporting low voltages at different bulbs I still strongly suspect you have a poor connection somewhere, but it could be an actual wire that is corroding and presenting a high resistance between the plug and the lights. I have seen some wires that look fine, but have actually corroded inside the PVC jacket rendering them a high resistance.

I would remove all the bulbs, and using a multi meter. I would check the resistances of the wires from the plug to their respective light bulb sockets. I would expect a good circuit to exhibit less than 1 Ohm. resistance. Any circuit that shows more then 1 Ohm is suspect, and connections should be rechecked. If cleaning and remaking connections does not resolve the reading, the wire its self must be suspect. In practice I would expect a 12V circuit in a caravan to show a resistance of less than about 0.5Ohms, but not every one has access to meters with that level of sensitivity.

 

[jseaman]

Thanks, I agree with the wire being suspect, I'll do a resistance check next

Assuming the diagram is correct on the link you provided then it's got to be earth related for the front as they are both fed from the two lives which I am putting +12V down so at least one should light up

 

[ProfJohnL]

Hi James,

Please don't assume your caravan conforms to the UK wiring standards shown in the diagram. I recently worked on a foreign van where the wiring was a nightmare. The colour of wires was not maintained through junction blocks, and some of the blocks were totally inaccessible having had furniture built over them.

Metal surfaces such as the cooker hob was not grounded, so the ignition spark had no direct route back to the ignitor, instead it had to jump between the hob's base plate and the fridges control circuit, damaging the expensive circuit board!

So please don't assume, check with your meter.

 

[jseaman]

I fully expect the same issues with access based on what I have seen so far! Of course will check with the meter

 

[Beachball]

Welcome to the forum James

 

[Craigyoung]

But could it not possibly be bulb connections that are a bit old and rusty where they push/twist in ?

 

[chrisn7]

You followed the cable from the 7 pin plug to the van, and this should end in a road lights fusebox. (at least it does on UK vans). Might be worth finding the end of the 7 core cable to see if there any faults or corrosion there.

 

[jseaman]

No sign of a fuse box as far as I can see and no mention in the manual