 | Home > In Car Electronics > Trailer warning light |
 
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| custom90 Member Since: 21 Jan 2010 Location: South West, England. Posts: 19578  
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I assume you are running LED Defender lights and relay? And incandescent non LED trailer lighting.
If so, then I’d consider changing the Relay. Also try adding in a temporary earth, if that cures it then track down the rear lighting grounding point. I have had this before. Usually it is the grounding point that is loose, on mine it is on the sid of the transfer box and twice the stud had come loose despite being tortured correctly. So last time I solved it I used a little bit of low strength loctite. Hopefully that will solve it. Can’t guarantee that’s the culprits but it’s possible. The other issue could be water, in particular in the back of the tow socket. On mine I took it off, replaced it with an aftermarket one (which has test LED’s built in the socket) and silicone sealed all the connectors completely (once collected so connections were made and then wet reassembled so that there was no void any moisture could accumulate. I’ve not had any issue since. Hope one of these things might help.  Diesel$ Live$ Matter. ⛽️🛢️👨🔧🧰⚙️ RED, WHITE & BOOST! 🇬🇧 |
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1st Jun 2021 10:12pm |
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| barbel jim Member Since: 12 Dec 2012 Location: Northants Posts: 1411 
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Cheers Steve
No leds old school I’m afraid 
No water in the plug backplate it’s new and hasn’t got wet yet. Sounded like an earth issue, but I’m confused by the light illuminating ? |
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1st Jun 2021 10:29pm |
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| custom90 Member Since: 21 Jan 2010 Location: South West, England. Posts: 19578
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The light is triggered by load, increased load should put it on and decreased load keep it off.
If you had a Wipac or RDX Relay you can adjust the trailer light with them useless you already do? As far as I’m aware they are backward compatible too. It sound to me like there is an increased load on the circuits if it’s common then it is likely ground like you said but tracking that down is tricky. Have you tested the ground impedance and see what reading it gives? When I had this it was defiantly the rear loom ground, it tested out okay but in use under load caused problems. The multimeter didn’t find it as it only happened when there was a load on the ground line and there was only then highnresstanc din the ground line due to poor connection. I’d suggest an adjustable LED relay (check if they can be used backward compatible I believe they but don’t quote me on that). That should help solve the issue until you track down the culprit. Or you could disconnect it and use a buzzer I believe which is also legal. Diesel$ Live$ Matter. ⛽️🛢️👨🔧🧰⚙️ RED, WHITE & BOOST! 🇬🇧 |
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1st Jun 2021 10:57pm |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 16879 
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You have an earth fault on the trailer or coupling on the nearside lighting circuit (hence the brake lights earthing through the tail light filament).
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1st Jun 2021 11:11pm |
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| barbel jim Member Since: 12 Dec 2012 Location: Northants Posts: 1411
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Thanks for the pointers
The fault has to be defender side, as I do tow different things, and experience similar symptoms. Just need this find some time now |
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2nd Jun 2021 6:44am |
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| jeffersj Member Since: 23 Jan 2015 Location: Near Preston Posts: 431 
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Have a look at the wiring in the rear corners (inside tub) and clean up or tidy all of the earthing connections. I had the same problem so used canbus bars to connect several to a good ground. Jeff
Ex 1968 Series 2A Ex 90 TD5 Ex D3 Ex D4 |
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2nd Jun 2021 8:21am |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 16879
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In that case check the earth connection to the trailer socket. You definitely have an earth fault, it is the only thing that will cause the tail/brake light phenomenon. The odd behaviour of the indicator warning light will be because the earth path for the indicator lights also involves brake or tail light filaments due to the earth fault. |
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2nd Jun 2021 9:06am |
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| custom90 Member Since: 21 Jan 2010 Location: South West, England. Posts: 19578
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Might be worth cleaning all the pins and connectors with alcohol wipes too.
When I had the Earth fault I had it twice and found it to be the rear lighting ground stud on the RHS of the transfer box. I added an additional Earth on top of that too. And low and behold it happened again a few years later. Is the TD5 stud in the same location as the 2.4? Or where there changes. If it is the same it’s easy to get at. Funniest part is, when tested it would check out okay but that was because there wasn’t a load on it. Then I checked each rear indicator ground and found they had a vastly different impedance and that’s what led me to the rear lighting ground stud. It’s the same one that once had all my lighting and dash light up like a Christmas tree while left loose by LR after a clutch change.. Diesel$ Live$ Matter. ⛽️🛢️👨🔧🧰⚙️ RED, WHITE & BOOST! 🇬🇧 |
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2nd Jun 2021 2:16pm |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 16879
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If the fault was with the earth stud on the t-box it would affect the vehicle rear lights as well as the trailer. I think, from the description, that the fault lies within the trailer harness on the vehicle.
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2nd Jun 2021 2:54pm |
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| barbel jim Member Since: 12 Dec 2012 Location: Northants Posts: 1411
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 Click image to enlarge Well I thought I’d found it discovered at work between jobs. Was feeling smug went to drive home and ever time I used the brake all the sidelights came on . No worries stick the lights on and everything worked ok. Came home whipped of the wheel cut out damaged section and joint in another sorted ...... or so I thought   no change off for a cuppa and a look at the workshop manual |
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2nd Jun 2021 7:30pm |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 16879
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If it is doing it without a trailer, check the earth connection at the stud on the transfer box (offside of the vehicle). I had the impression from what you said that it only did it with a trailer on.
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2nd Jun 2021 8:47pm |
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| barbel jim Member Since: 12 Dec 2012 Location: Northants Posts: 1411
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The trailer warning light has been with and without the trailer at random points. Last 2 days was after indicating, but not every time, and again with and without the trailer. The sidelights is new fault, probably because I’ve wiggled wires
So latest update.... after the repair to the n/s indicator that didn’t cure the sidelight issue, I kept the brake pedal down and removed the trailer socket plug, n/s indicator, reverse and stop/tail. I then did the same on the off side, and when I pulled the stop tail all the sidelights went off (not that there was many left ) leaving that out I replaced all the other lights without issue, so at least I know it’s offside stop/tail which will be tomorrow’s job. There is an earth post according to the workshop manual in the wheel arch somewhere. |
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2nd Jun 2021 9:30pm |
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| barbel jim Member Since: 12 Dec 2012 Location: Northants Posts: 1411
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I’ve given it a wiggle seems solid enough made no difference when it was all lit up. |
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2nd Jun 2021 9:33pm |
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| barbel jim Member Since: 12 Dec 2012 Location: Northants Posts: 1411
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Click image to enlarge Taken from td5 workshop manual. Fingers crossed it’ll be obvious once I take the wheel off and can see |
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2nd Jun 2021 9:35pm |
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