G'day Fellas,

I was towing my Caravan (Trailer) recently with a mate of mine following behind with his Colorado & Caravan.
When we pulled over for a break he said 'don't you ever your brakes?'

He asked this because we always do a trailer light test after hitching up and before moving off.
Indicator Left, Right, Brake & tail lights checked all good.
So jumped in and tested again, All good? WTF
However it had started drizzling a little not long after leaving that morning, so I'd put on my headlights.
That being the only change from the check before taking off. So I put my headlights on and did the lights check again.
Indicator Left, Right ok, Tail lights on and good. However no brake lights came on
Turn head lights off and all good. Does the same if just park lights on.

So, has anyone encountered this odd issue.
That is; All lights and indicators work fine without head or park lights on. Put head or park lights on and you lose the 'Brake lights'???

Cheers
Reg
"Socialism is a philosophy of failure, the creed of ignorance, and the gospel of envy, its inherent virtue is the equal sharing of misery."fficeffice" /><O></O>
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Aussie spec Brazilian built 2005 (US 2003) F-250 Superduty 4x4 7.3Ltr Powerstroke: PHP FU2 6Pos on the Fly Chip, 6 x ISSPRO Promax Guages, Donaldson (AIS) Intake with Zoodad, Hutch'd n’ Harpoon'd, Cowl Hood, Billet Grill, AIH delete, DIY CCV & catch can, Straight Through 3½” Cummins muffler, MBRP Black Tip, RiffRaff FRx,OCR,HPx, JWVB, OME Suspension, Dual Tower shocks, Tough Dog RTC Steering Damper, ARB Air Lockers Front & Rear, V10 Tranny cooler in series with Stock Tranny cooler, BD Deep Pan, Extra Cooling rear diff cover, ARB HD Front Diff cover, ARB Bull Bar, Kymar Dual Spare Wheel carrier & Rear bumper, Edge Evo Dash Pod (used for PIDs/Codes only), Long Range Fuel Tank, OEM Style paint matched wheel arch flares, VMS in Dash GPS Street & Off Road Navigator, Toyo OPAT AT 305 70R 16” on 10” Rims. GVWR (GVM) Upgrade to 5,000kg(F350).

 

G'day M8!

I was a USN Avionics tech for 20 years and a month, so I know a bit about the weird things electricity will do. It was my job day after day to sort out what went wrong right down to individual transistors, resistors, and the like inside of very strange devices.

THIS to me, sounds like a wire was tapped into during the trailer light install that should have been left alone.

I also rather HIGHLY suspect that it isn't anything to DO WITH the headlights at all - the same circuit controls every one of your side and top marker lights. From what you have said, it is THEM that are messing things up.

You've got an incorrect wire cross somewhere in there... Most likely between a side marker or tail light and a turn and brake wire

It DON'T have to be a wrong installation either, it could be a pair of wires that have been cut into or shorted together some way, but the money is on a bad setup.

I would cut the entire trailer harness out (or at least the wire for the brakes, and do it over), and reinstall it carefully and by the numbers from scratch were I you.

~Hope something in there works to the good!

~Dutch J. from the USA

 

G'day Dutch,

Thanks M8, I'll check all this out when I get back home.
I've got 5 more weeks at sea to go.
I'll let ya know how it goes.

Cheers,
Reg

Ineptocracy <O</O
(in-ep-toc'-ra-cy) - a system of government where the least capable to lead are elected by the least capable of producing, and where the members of society least likely to sustain themselves or succeed, are rewarded with goods and services paid for by the confiscated wealth of a diminishing number of producers.

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Aussie spec Brazilian built 2005 (US 2003) F-250 Superduty 4x4 7.3Ltr Powerstroke: PHP FU2 6 Pos’n Chip, 6 x ISSPRO Promax Guages, AIS Intake, Zoodad, Hutch'd n’ Harpoon'd, Cowl Hood, AIH Delete, DIY CCV, BTM muffler, MBRP 4” Black Tip, RiffRaff FRx,HPx,OCR, JWVB, ARB Air Lockers Front & Rear, V10 Tranny cooler in series with Stock Tranny cooler, Deep Tranny Pan, ARB Bull Bar, Edge Evo (for PIDs & Codes only), Long Range Fuel Tank, VMS in Dash GPS Street & Off Road Nav, Toyo OPAT AT 305 70R 16”on 10” Rims, Moog Greasable Ball Joints, Tough Dog RTC Steering Stabiliser, OME Suspension & Dual Tower Shocks, GVWR (GVM) Upgrade to 5,000Kg.
<O</O

 

I would suggest a more conservative course, as there has not been enough diagnostics done so far to start cutting, in my opinion. I would start with a meter and take voltage readings at my seven pin with the headlights off and on to see if I have a complete absence of voltage or a significant drop at the pin for the brakes. I would also check the wiring on the trailer, which is very easy to do, to make sure everything is as it should be. That would be seven pin plug to junction box and then connections in junction box. Those steps will tell you whether the problem is truckside or trailerside, which so far does not seem to be clearly established.

I encourage folks to consider the simplest possibilities first, before moving on to other possibilities. Electricity is indeed funny stuff and always goes the way of least resistance. When you open a pathway to the headlights or marker lights, the brake lights go away. The interesting question is why. Is there a voltage drop so a weak pathway offers too great a resistance or is there no voltage at all which makes a crucial difference.

My thoughts,

Steve

 

Just thinking about what RV_Tech Steve said above.

Could be, ON THE TRAILER, if the brake light wire is connected/shorting to the taillight filament of a brake-tail bulb.

Try swapping trailers over with your friend (just for the test).

Does the problem follows the trailer? or,
Does the problem stay with the vehicle?

If all the lights work fine on his trailer when connected to your car that would prove that the wiring on your vehicle is OK.

If your friend's vehicle causes the same 'no brake light when lights are on' problem then the problem is on your trailer. Check the tail/brake light fitting first up and make sure the correct filament is lighting - the brake light filament should be brighter than the tail light filament.

If your vehicle makes your friend's trailer have the same problem, then the problem is on the vehicle side of the trailer plug. So you'll have to check the plug wiring to your vehicle.

 

I think this is an excellent suggestion as it is always better to know what the problem is before trying to fix something. I do my testing with a meter, but using a trailer known to be good certainly works just dandy!

Steve

 

Thanks Steve!

I better add to my suggestion,

before swapping trailers, make sure that all the lights, including brake light when headlights are on, are working on your friend's trailer when attached to his vehicle

- to make sure it's a 'trailer known to be good' before hooking it up to your vehicle.