Van stop lights working...then not working

[AddItUp]

Hi everyone

We have been having intermittent problems with the stop lights on our 2013 17.56-1 not working. Today I measured 13V across pin 3 (earth) and pin 6 (stop light) of the tug plug with the engine going and pressure on the brake pedal. I plugged the van in and the stop lights worked ok.

For some reason, I thought I would unplug the tug/van and then re-plug again. Guess what? The stop lights no longer worked. Then I measured 0V across pins 3 and 6 (with the van plugged into the tug). When I removed the van plug, the voltage across pins 3 and 6 was now 7V.

I tried spreading the van pins slightly but it didn't change anything.

Any ideas on what is going on and how I can fix it?

Van: 2013 17.56-1
Tug: 2010 Territory

Thanks, Wayne

 

[Capt. Gadget]

Possible a loose wire at the back of the plug on the tug ?

 

[Marv_mart]

Had a friend with a similar problem, they worked ,then didn't then worked then didn't.
Oops, indicator light. LOL
Sorry, know your issue is a serious one, only hint is a loose wire. Or bad earth somewhere.

 

[AddItUp]

Thanks @Capt. Gadget
...and haha @Marv_mart
I will have a closer look at the wires.

 

[cruza driver]

Have a look in the back of the plugs both the van and car also. There maybe a poor contact in there.

 

[Hubble80]

If all your other lights work I would say your earths are ok. Do the lights on the tug work everytime???

I would check for corrosion in socket on car and If so, replace the socket. Cleaning and the like only delays further failure in my opinion.

 

[AddItUp]

The tug lights work every time @Hubble80
I'll check for any signs of corrosion in the socket.

 

[Marv_mart]

Same thing happened on my boat, turned out the wiring loom from the car socket through the frame to the tail lights was corroded. At last service, they checked and completely rewired from front to rear. That was a boat trailer though and you would expect corrosion over time as the trailer gets dunked in sea water regularly. Still .....

 

[straydingo]

I had the same when going away for cup weekend last year - the connections inside the plug on the van was very corroded. Replaced and all good since.

 

[AddItUp]

Thanks @straydingo I'll take a closer look.

 

[Rockape]

Hi,
Do your tail lights still work? I assume you have led tail lights being a 2013 model. If your tail lights work, and your connections are ok, it could be your brake controller causing the issue. You can try applying 12 volts to the trailer plug direct. +12v to pin 6 and - 12v to ground pin 3 if you are comfortable. If not read on. Your brake controller activates the trailer lights and brake lights when you manually activate your brake controller. When you put your foot on the brake panel, your brake switch on the foot pedal actives the vehicle brake lights and the brake controller activates the trailer lights. Simply put manually activate the controller and then use the foot pedal and see what happens. I have also found that the screws that secure the wires in the connectors can work loose causing issues. I have a test plug that plunge into the trailer to check lights that you can use if you are located in Sydney.
Hope this helps.
Cheers
Nick

 

[AddItUp]

Thanks very much for your detailed reply @Rockape
Yes, the tail lights work. I thought the brake controller may be causing problems, so I unplugged it but the stop lights still didn't work.
I borrowed a test light last night and put it across the stop light pin and ground pin on the tug. It didn't light up even though the multimeter showed 12V. So I think that means there is a loose connection. I didn't have a chance to look closely but I will check the screw this weekend to see if it is loose. Or maybe there is some corrosion there?
Thanks for the offer of the test plug but unfortunately I'm in Melbourne.
Cheers, Wayne

 

[Rockape]

Hi,
I have just checked my brake controller and found that it does not supply the power to the brake lights on the trailer, but power to the brakes only. When the brake controller is manually activated it should light up all the brake lights as does applying your brake pedal. If your brake lights on your tow vehicle are working and not on your van then it is most likely an issue with the wiring to the rear of the tow vehicle or caravan connection. Sorry for the incorrect info, been a very long week! You can simply hook up a box trailer and see if that works to rule out the caravan.
Cheers
Nick

 

[AddItUp]

No worries @Rockape , I appreciate your help with this.
I'll see if I can borrow a trailer and eliminate the caravan from the equation.
Cheers, Wayne

 

[Glen Bundesen]

Your Brake Controller is using the Blue wire (pin 2 I think) for your electric brakes while your Brake Pedal is giving power to your Stop lights [red wire] (pin ?)

 

[AddItUp]

I had a closer look today and pulled out the stop light wire from pin 6 on the car plug...and low and behold water came out. Whoo hoo I thought, problem fixed. I sprayed some contact spray, cleaned the socket with a little brush and waited for everything to dry. Put it all back together and still only measured 7V across the stop light and ground pins when the brake was depressed.

Then I had a closer look at the wires they used to connect the brake controller to the car and guess what I saw? A Scotchlok. Whoo hoo I thought, problem fixed. I replaced the Scotchlok with a terminal block and still only measured 7V across the stop light and ground pins.

We purchased the car second hand and it appears to be factory wired for the plug. I'm not sure where they pick up on the stop light signal in the car but it appears to be somewhere at the front as that's where the loom heads off to.

Can I run a wire directly from pin 6 on the car plug and splice it into the positive wire which leads to the car stop light?

Thanks, Wayne

 

[Glen Bundesen]

My installer spliced all the plug wires into the loom for the back tail light (except for electric brakes and 12v power).

 

[AddItUp]

Thanks @Glen Bundesen I may have to look at that option.

 

[AddItUp]

I have solved the problem...fingers crossed.
I spliced a wire into the positive from the car stop light and ran it to the car plug. Now I have 13V at the car plug. Hooked up to the van just in case and the lights worked!

 

[seanparky]

so to the original problem did you find the fault. A lot of car dealers when wiring up trailer plugs use scotch locks. Basically to find the fault you need to follow the wiring loom from the trailer plug on your car to the end where it is joined. the fault will lie at the connection point at the end of this harness. If this is ok there is a break in the loom.