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Old 09 December 2009, 06:01   #1
Country: UK - England
Town: Southport
Boat name: Qudos
Make: 5.4 Searider
Length: 5m +
Engine: Yam 115 V4
MMSI: 235068784
Join Date: Sep 2008
Posts: 3,930
Adding an earth wire

I've got a problem with my lights on the trailer. If I have the side lights on and apply the brake all the lights go off on the lighting board. Searching the net it seems it's due to the earth on the car/socket not being up to the job.
I've read a few times about adding an earth wire from the lights and bolted to the frame of the trailer. No need to say that this isn't really an option on my boat trailer due to having to remove the lights before launching. And I don't want to be unbolting stuff at ever launch.

Any one any ideas on running an earth to the car instead? Would an earth wire from the lights to the towbar frame work? Attached by some sort of small clamp a bit like the earth clamp on a welder.


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Old 09 December 2009, 06:24   #2
Country: UK - England
Town: Bursledon
Boat name: Mustard
Make: Ribeye 785
Length: 7m +
Engine: Yamaha 200/Merc 6
MMSI: 235068693
Join Date: Oct 2006
Posts: 618
If I may add my tuppenceworth to this...

Rewire the lot. If everything is wired propely, it all works. Any other solution is a bodge and only moves the issue along the line somewhere.

We are towing thousands of pounds worth of baot behind a car worth lots, all you need is crossed oindicators or faulty brake lights and you are in a very vulnerable situation.

Or buy a new one, for what they cost!

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Old 09 December 2009, 06:31   #3
Country: UK - Scotland
Boat name: Wildheart
Make: Humber/Delta Seasafe
Length: 5m +
Engine: Merc 60 Clamshell
MMSI: 235068449
Join Date: Apr 2007
Posts: 4,539
Yeah, the old "earth it to the body" trick works on a car brecause the battery is attatched to the car body. the fault is usually in the earth - body connection on the light fitting. Problem with a trailer is that the "body" connection to the battery is through a greased hitch.....

On your trailer board, the earth is via the earth pin on the socket. I;d suggest (in this order)
1) use a flat screwdriver to GENTLY prize open the split on the pins on both plug & socket.- not too far, just enough to get a good tight fit.
2) dismantle the trailer lights, check all connections are sound / not corroded. also check the pathetic bent bits of metal that hold the bulb haven't lost their spring, bend back as required.
3) dismantle the trailer plug, check all connections are sound / not corroded. If i n doubt, chop half an inch off the end of the cbale & rewire.
4) if that lot hasn't fixed it, repeat (3) with the socket on the car.

Thing with boat boards is that they generally are in the ~2m long category, so the "cheap'n'heerful ones don't normally fit, or have a huge 3m of cable on the end.
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Old 09 December 2009, 06:46   #4
Country: UK - Wales
Town: West Wales
Make: Vipermax 5.8, SR4.7
Length: 5m +
Engine: 150 Opti, F50EFi
Join Date: Sep 2005
Posts: 6,298
Agree with everything 9D280 says. The problem is usually in the bulbholder, but the 7-core cable is also prone to corrosion on the plug terminals.

The Roguester would recommend tinned wire for the 7-core
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Old 09 December 2009, 07:34   #5
Country: UK - England
Town: York
Boat name: Sugar Free
Make: Tornado
Length: 5m +
Engine: Yam 115
Join Date: Sep 2009
Posts: 118
I had problems with mine too. The resistance in the bulb is relatively low hence any additional resistqance causes problems.

The screw driver prising the pins out is a good recommendation, careful they don't break though.

A good electrical meter can help measuring the earth resistance from Battery to socket and then battery to light board. etc.

Cleaning all contacts makes a lot of difference. I bought a very small wire brush that goes into a cordless drill. (like a dentists)
Cleaning the plug and socket pins (ensuring you dont short the car socket side pins) got mine working perfectly. Any corrosion file it off.

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Old 09 December 2009, 07:38   #6
ashbypower's Avatar
Country: UK - England
Town: Salisbury/Poole
Boat name: Blue C
Make: XS 600
Length: 6m +
Engine: 125hp Opti
MMSI: 235082826/235909566
Join Date: Jan 2004
Posts: 1,439
Hi JSP it would be well worth Checking the Socket earth on the tow vehicle, some installers will earth underneath rather that inside, this resistance can also cause problems.......
Tip: I always fill the the back of the Socket & the PLUG with Silicone Sealant, helps take the Stress and Keeps the inside DRY.
As others have said seems a good time to revamp the wiring.

Good luck with it.
Brian C
Harbour Sea School & APS Marine Centre
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Old 09 December 2009, 09:41   #7
Country: UK - Wales
Town: Southampton
Boat name: DynaMoHumm/ SRV/deja
Make: Avon8.4, 5.4 & 4.777
Length: 8m +
Engine: Cat3126 Yam 90 &70
MMSI: 42
Join Date: Dec 2003
Posts: 6,533
Originally Posted by Downhilldai View Post

The Roguester would recommend tinned wire for the 7-core
If I could make the board last longer than a coupleof trips I would but Asbydeladouche's solution is what I do. I'm just renewing my tow connectors and building a new light board. ATM

I'm confident this one will last at least 3 trips
Here it comes again, I don't stand a chance
Soul possession, Got me in a trance
Pullin' me back to you - Deja Voodoo
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Old 09 December 2009, 10:42   #8
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Country: Other
Town: Principalite d'Chaos
Boat name: The Nashers Revenge!
Make: Ocean & Bombard
Length: 6m +
Engine: Suzi DT200EFI, DT9.9
MMSI: "Mmmmm SI" she said!
Join Date: Jan 2004
Posts: 4,142
I must be really lucky.

My cheap 3yr old towsure lightboard has only let me down once when a taillight bulb blew.
When I first brought it I extended the cable by splicing in an extra 4M of cable and refitting the plug on the end.
The soldered joins were covered in heatshrink then the whole thing covered in a larger Heatshrink.

Despite the care I take of the boat, engine, and trailer Iíve never really taken any notice of the light board.
Probably because I have a spare in the garage that somebody gave me soon after buying it.

The only care and attention itís had was a squirt of WD40 inside the bulb holders about two years ago because they had a little tiny bit of green inside that I noticed when the bulb blew.
I gave up removing it from the trailer when the boat is at the yard about 2 years ago, so itís outside in all weathers and all I do is dangle the plug over the winch where the cover protects it from the rain. Itís been up and down between Pompey and Dartmouth several times in horrendous rain at a steady 60mph, gets used all year round for journeys of @15miles at a time, and so far has always worked first time when Iíve plugged it in.

The electrics on the car were however professionally fitted when the car was 3 months old and all the connections are inside protected by rubber grommets and connected into the Mitsubishi loom properly, not with crimps or those silly Blue things.

RIBBED For extra pleasure.
Member of the ebay Blue RIB cover club.
Member of the Bombard 380 Aerotec club
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Old 09 December 2009, 10:48   #9
Country: UK - Wales
Town: West Wales
Make: Vipermax 5.8, SR4.7
Length: 5m +
Engine: 150 Opti, F50EFi
Join Date: Sep 2005
Posts: 6,298
Sounds to me like Nasher's doing the clever thing and taking the lighting board off, when launching.

Similarly, I've never had to replace a lighting board, due to terminal failure
but that's probably 'cos the boats live indoors all year round.
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Old 09 December 2009, 10:48   #10
Country: USA
Town: Oakland CA
Length: 3m +
Join Date: Feb 2005
Posts: 6,621
What kind of cable are you using on the trailer?

Here in the states, "standard" is a 4 conductor cable: Left turn, Right turn, running lights, and ground. Upgrade from that is a 5-wire system that adds a reverse signal (usually for locking out disk brakes.) Connector is a flat-4 or flat-5 (three or four sockets for the signals, and a single pin for the ground; reversed for the mating connector. In a bind, you can connect a 5-wire trailer to a 4-wire tow vehicle, but you lose the brake lock-out.)

On both those systems, the ground wire runs from the trailer's connector and is almost immediately terminated to the trailer frame. All lights are connected to their respective signal wires (either turn or running), and tied back to the frame. End result is a lot of connections to a piece of hot dip galvanised steel, which makes for a sketchy connection from the start; add in a bit of corrosion and problems become inevitable.

On my trailer, I've added a separate run of ground wire to each light fixture, such that each has a dedicated signal and ground wire (that doesn't sound right - what I mean is there is a ground wire down each side of the trailer that is daisy-chained to each fixture.) The ground wire is still tied to the frame, but it doesn't really do anything. I've had very few flaky ground problems (having the LED light fixtures flood is another story...)


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