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gavinwibrow
12th January 2021, 12:57 PM
Weird Trailer Wiring

Considering the various wiring bits were done by 3 separate electricians, guess I should have expected something like this - maybe Tim @ Traxide has a logical answer/explanation?

1 - about a year ago after purchase, had connections fitted including ESC to the D4, to enable towing the van.

2 - just recently, had resistors added so the car would recognise the van with its all LED lights arrangement.

Pre last trip, I was travelling home after picking up the van from storage, and a kind motorist told me that both L & R indicators came on when I indicated to turn left (I won't know about right turns until I check later today, because I forgot to check at the time after resolving the initial problem as below).

I then turned on the forgotten to do "in car" over-ride switch to activate the resistors and bingo all is well/indicators working perfectly - (all of my towed bits are now LED lights, hence the in car switched resistors approach, with still the ability to tow non LED by switching off the resistors).

I doubt the "all indicators on" scenario is intended to occur when the LED control switch is in the off position, so presumably there must be a wiring error somewhere?

Tombie
12th January 2021, 01:15 PM
Sounds like either a diode has failed (if they did common earth) or they wired incorrectly on the resistor pack.

GIL
12th January 2021, 01:17 PM
Hi Gavin,
I'm going to guess here.
When the 2 resistors were installed the ground ends were commoned then wired through the (single pole) switch to ground itself.
When NOT switched the Left and Right Indicators are effectively connected together and the resistors are not connected to ground.
When switched the resistors are connected to ground and work fine.
(Ask me how I know).

The solution: get a double pole switch and use a pole for the Left resistor and the other pole for the Right resistor. You can the common the ground to the other side of the 2 poles.

Now , when NOT switched each of the left and right circuits are still independent.
When switched the resistors are connected to ground and will work fine.

Also check a diode is installed to block feedback to the CJB from the trailer brake system.
See this the D3-D4 Electric trailer brake sticky.
D4 Electric Trailer Brake Wiring (https://www.aulro.com/afvb/the-d3-d4-sticky-zone/97935-d4-electric-trailer-brake-wiring-69.html)

Hope I,m right 'cause its an easy fix.

Regards
GIL

kelvo
13th January 2021, 08:49 AM
Hi Gavin,
I'm going to guess here.
When the 2 resistors were installed the ground ends were commoned then wired through the (single pole) switch to ground itself.
When NOT switched the Left and Right Indicators are effectively connected together and the resistors are not connected to ground.
When switched the resistors are connected to ground and work fine.
(Ask me how I know).

The solution: get a double pole switch and use a pole for the Left resistor and the other pole for the Right resistor. You can the common the ground to the other side of the 2 poles.

Now , when NOT switched each of the left and right circuits are still independent.
When switched the resistors are connected to ground and will work fine.

Also check a diode is installed to block feedback to the CJB from the trailer brake system.
See this the D3-D4 Electric trailer brake sticky.
D4 Electric Trailer Brake Wiring (https://www.aulro.com/afvb/the-d3-d4-sticky-zone/97935-d4-electric-trailer-brake-wiring-69.html)

Hope I,m right 'cause its an easy fix.

Regards
GIL
I’ll put money on a single pole switch being fitted is the reason it’s bringing both indicators on.

gavinwibrow
13th January 2021, 10:29 AM
I’ll put money on a single pole switch being fitted is the reason it’s bringing both indicators on.

Thanks all for replies. Will check with the installer in a couple of weeks when we go past in our travels. I'd bought a double pole switch, but could not find it on the day, so they fitted one of theirs, so quite possibly a single. Will feedback once resolved.