Please Help me, car trailer wiring woes

[Roctoy]

this is how my trailer is wired up, there must be a problem with the earth return at the vehicle end because all the stop lights, turn signals etc work as they are supposed to when switched on one at a time. But when you turn the parkers on, they work ok, put your foot on the brake and the parkers go out, the indicators come on and the brake lights don't work. Turn the blinkers on while the lights are on and every thing flashes opposite, this is doing my head in.

here's a drawing of the trailer setup, i'm sure it's right.




can anybody offer any help?

if the problem is at the car end, where EXACTLY should the wires for the trailer be connected to?

Cheers Chris

[Toy80Diesel]

Ummm.... Firstly, Check that the trailer plug at the vehicle has an earth!

Looks like the trailer end is fine to me.

[Roctoy]

it does, but i can't tell where it is actually earthed to.

Where should the wire go? Silly question i know, but is there a 'best spot" to earth it? Tow car is a GQ.

Chris

[Toy80Diesel]

Just make sure the earth pin on the car has a good earth point. Somewhere on the chassis near the plug is fine. You should find some factory ones for the rear lights, maybe just unscrew one and put your earth wire on the same screw. Use an appropriate round lug on the wire.
Make sure its nice and tight.

Also, sometimes the pins in the 7pin plugs need to be opened a little to make better contact.

[Roctoy]

thanks for the reply, would having the earth from the trailer wired into an earth from say the tail lights on the car cause the trailer lights to go all fubar?

[-Scott-]

I don't remember the brand name, but there's a mob now who make plastic trailer plugs and sockets with LEDs built in. For $8 (from Sprint Auto) you can buy a commercial "tester" to tell you if the socket on your GQ is working properly.

They also advertised in the latest 4wd Monthly, if that helps.

Good luck,

Scott

PS I agree with the others - you have an earthing problem. Try jumper cable from trailer chassis to vehicle chassis?

[Toy80Diesel]

thanks for the reply, would having the earth from the trailer wired into an earth from say the tail lights on the car cause the trailer lights to go all fubar?

Could be the earth on the taillights isn't up to scratch and if so, its probably not good enough to run a whole bunch of trailer lights as well. Thats why a seperate, better earth is required.

Try the jumper cable idea, it couldn't hurt.

[Roctoy]

thanks for the reply, would having the earth from the trailer wired into an earth from say the tail lights on the car cause the trailer lights to go all fubar?

Could be the earth on the taillights isn't up to scratch and if so, its probably not good enough to run a whole bunch of trailer lights as well. Thats why a seperate, better earth is required.

Try the jumper cable idea, it couldn't hurt.

yeah i tried that last nigh and it didn't seem to make any difference, i ran a wire from the earth at the trailer end plug to the chassis and it still did the same thing...

[Roctoy]

yep, definitely an earth problem though, up until last night i never actually had the trailer connected to the tow bar, it was just plugged in through the plug. When hooked up to the car it all worked fine, so it passed roadworthy yesterday.

I will sort the problem out later, cheers

[Toy80Diesel]

yep, definitely an earth problem though, up until last night i never actually had the trailer connected to the tow bar, it was just plugged in through the plug. When hooked up to the car it all worked fine, so it passed roadworthy yesterday.

I will sort the problem out later, cheers

The tow ball creates a link for the earth so yeah, its definitly an earthing problem. Although tow balls don't create a perfect earth due to grease etc in there. So when you have more time to look at it more thoroughly, check the earth cables in the car. The one from your battery to the chassis in particular. Doesn't hurt to add another earthing cable somewhere else as the factory one is really only there for the standard vehicle, and we tend to accessorise..