Trailer wiring troubleshooting

JCB1

Hi,

I'm looking for some pointers on how to troubleshoot a trailer wiring issue, when I put on the lights individually - parking lights/brake and indicators are all fine but when I put on the indicators and press the brake or put on the side light - there is a slight flicker on the red light. The flicker is in synch with the indicator flash and happens on both sides. Any ideas ? Is it an earthing problem or a bare wire somewhere ?

Thanks

bbam

I'd say this an earthing problem.

See if you can improve the earthing on each of the lighting units and see how it goes.

JCB1

Thanks bbam, further update, it looks like the problem with the wiring on the Jeep side, I just tested with another trailer and the exact same problem exists. Could it be a simple issue with the socket on the jeep ? Or is it a wiring issue where the wires are connected to the lights ?

I've got my trailer test on Thursday so am starting to worry....

Muckit

Well at least you've it pin pointed to the jeep side

Lights are so finicky. The slightest bit of wear in a cable, poor connection coupled with rust and water problems this time of the year can all play havoc with trailer wiring...... and a person's sanity!

I'd say remove the panels behind the rear light clusters on your jeep and locate where the wires have been spliced into to wire the plug. Usually on the LHS, but could be done from either. These very possibly were done ad hoc and are now giving trouble. Ideally the splicing should be done inside the jeep here where there are no issues with water. Soldered and heatshrunk joints are always better than twisting wires together and using insulating tape.

I would also advise wiring on a new plug to jeep, one wire at a time. Things have to be right on the day.

The simplest thing is causing the problem.

Best of luck with the test!

pakalasa

'Switch Cleaner Spray' often works for me. Just spray it into the pins and sockets and presto !!! Gets rid of the layer that builds up to prevent a good connection.

bbam

Interesting.
Well I'll stick with a trailer problem.

If there were a problem at the light cluster or socket then it would be there with no trailer at all. I've seen that happen but you haven't indicated if there is any problem with the vehicle lights with no trailer connected??

If the problem only happens when there is a trailer connected it mist be the trailer.

JCB1

Thanks for all the input.

No - there is no problem with the jeep lights when the trailer is disconnected. But it is strange how the exact same problem shows up for 2 trailers ( I would consider the wiring and lights on both trailers to be in good shape), that is leading me to the jeep being the problem. But I see where you are coming from bbam, My plan is to replace the socket on the jeep but it will be tomorrow before I get to that.

reilig

Moisture in the plug or socket. On our jeep, if we haven't pulled a trailer for a few weeks then the exact same thing often happens. I keep a can of wd40 in the door pocket and a spray of it has always solved the problem so far!

JCB1

Thanks reilig - I will try wd40 this evening.

redzerologhlen

reilig wrote: »

Moisture in the plug or socket. On our jeep, if we haven't pulled a trailer for a few weeks then the exact same thing often happens. I keep a can of wd40 in the door pocket and a spray of it has always solved the problem so far!

+1 The lights on our trailer were flickering on and off with the last few weeks so I sprayed a bit of wd40 on the sockets the other day and its perfect since.

dzer2

A lot of trailer sockets are earthed to the hitch. On a lot of newer vehicles the hitch is attached underneath were anti corrosion paint is sprayed on the area where the hitch is attached this leads to a bad earth. you could try running a new wire to the earth pin and connect it to a defined earth place.

pakalasa

Serrated washer will help give a good earth connection too. They bite into the metal.

JCB1

Thanks for all the feedback.

Latest Update : I sprayed the sockets with WD40 but no joy. So I replaced the socket on the jeep side, I was sure this would be the problem as it was in bad shape when I opened it. But no - the problem still exists although it seems to have improved slightly in the the flicker is not so noticeabe but there still is a llittle there. So now I'm leaning back to the trailer being the problem again.

Muckit

Is it doing it still with the two trailers? It'd be great if you could try a friends or neighbour's trailer that you know is working perfect.

I'm sure you have already done so, but check the wire on the trailer side, especially around the hitch area. If it's a straight and not a coiled lead it could have dragged a little on the ground, torn the outer conduit and frayed wires inside.

For the few quid, I'd change the trailer plug. You could work a bit of sandpaper on the old pins, but this can be hit and miss.

At this stage, don't panic. You say the lights work fine when pressed separately. The instructor did not ask me to hold the pedal while working indicators, so he's not going to deck the problem. Anyways you say the your bit of tinkering has helped the problem, so no need to fret.

p.s. make sure to have a spare bulb kit with you in the glovebox. If an indicator or a brake bulb blows on your way there, you won't get out on the road. (oh, and don't forget the L plates!)

Again, best of luck!

F.D

best thing you could have around the place to test wiring is a cheap lighting board, even if its never used you use it to test off the jeep or tractor to see if the wiring is correct in the sockets, then you know straight away its the plug or wiring on the trailer or what ever your hitching up to is the problem, i agree with rellig too the wd 40 is a life saver

bbam

This is an earthing problem.
Check the earths on each of the lights, ensure they are good and clean with decent metal to metal contacts.

Failing this the system relies on the ground making its way back through the trailer chassis, through the hitch, to ground on the chassis of the vehicle.
You could ground the hitch to ye vehicle chassis with a separate ground wire. This would rule out and insulating of the hitch from the chassis with paint or under sealant.

I'd be 99.9% sure this is a ground problem.

JCB1

Again, thanks all.
My next step is to change the trailer socket and test with another trailer again.
As you say Muckit - if I'm sure not to press the brake while testing the indicators at the test I will be fine.
The flicker is almost not noticeable with the lense on so unless I'm very unlucky...
And good advice on the spare bulbs. Thanks

JCB1

Hi all,

Quick update - I've got to the root of the problem. When I hitched the trailer on to the jeep the lights are fine - no flicker at all, so it was most likely a combination of bad connections/moisture in the jeep socket and poor earth as the trailer was not hitched on to the jeep. Good advice on the earth bbam - you nailed it. Now to concentrate on studying the Ruls of the Road for tomorrow!
Thanks everyone for the sound advice.

bbam

Good luck with the test.

JCB1

Thanks bbam, good news is that I passed.
The tester will not check the parking lights if its daytime as they are not needed.
I can recommend a good instructor for Galway city if anyone needs one, I found the guy I used to be excellent. We did the exact testing route right before the test itself which was good.