matt1295 · Jul 12, 2014

just finished building my trailer and been and tested the lights

all the lights work with the engine running but if engine not running the brake lights dnt work on either the trailer or the car disconnect trailer work on car again connect it then nothing

any ideas

ZDomZ · Jul 12, 2014

Must be due to where the earth is taken from I would guess.

matt1295 · Jul 12, 2014

It's the earth on the plug no other as I bought a plug and play earth plus when engine off the rest of the lights work just not brake

Kizzeh · Jul 12, 2014

How often do you use the brakes with the engine off?

ZDomZ · Jul 12, 2014

I did wonder but I thought better of posting!

Most vehicles just require ignition on for brake lights to work. This is especially useful if you are being towed.

matt1295 · Jul 12, 2014

I just find it odd that it's only when the trailer is connected the brake lights dnt work unless engine running

Clearly it isn't right but dnt no where to start looking to fix the fault

longdog · Jul 13, 2014

Are you saying the brake lights work on your car with the ignition turned off?

Brack · Jul 13, 2014

My brake lights don't work with ign off

gstuart · Jul 13, 2014

something wrong there, my brake lights dont work either when the ign is off

sounds like youve wired the brake lights to a permanent live somehow , did u also replace the relay, not sure if possibly the old relay has become fused if it could cause a permanent live through to the brake lights

know the other more experianced guys will know more

??????

Kizzeh · Jul 13, 2014

I think a couple of people haven't read the original post properly.

Your brake lights only work with the ignition on. Matt is saying that his brakes lights work as normal unless the trailer is plugged in and they only work with the engine turned on but not with just ignition.

Have you tried to see if it's the same with another trailer?

matt1295 · Jul 13, 2014

I dnt have access to another trailer but my trailer is fine on a mates

GrumpyGel · Jul 13, 2014

Intrigued, I just went out in the rain - and can confirm that brake lights do NOT come on without the ignition being on - that's without a trailer, so can't see why you would expect them to with a trailer.

So you don't have a problem.

It would be expected that the other lights would work without the ignition on as warnings/hazards.

matt1295 · Jul 13, 2014

No car brake lights work when ignition off

I'm saying the brake lights work ign on and engine running but if my trailer is connected my brake lights only work when engine is running and dnt work if it isn't

Brack · Jul 13, 2014

If the bulbs in the trailer are a different wattage to the car brake bulbs - would this cause it?
:behindsofa:

englishbullterrier · Jul 13, 2014

Have you tested the trailer board on another vehicle with known good trailer electrics ?

dogsbody · Jul 13, 2014

Brack said:
If the bulbs in the trailer are a different wattage to the car brake bulbs - would this cause it?
:behindsofa:

No, that will only cause them to be brighter or duller.

matt1295 · Jul 13, 2014

cant be my problem as i have Freelander rear lights as my trailer lights

the wiring from the white connector to the socket is brand new replaced that yesterday as i bought a plug and play one

longdog · Jul 13, 2014

What happens to the cars brake lights if you remove the trailer bulbs?

matt1295 · Jul 13, 2014

We just had a huge down pour from no where so will answer that once it stops

GrumpyGel · Jul 13, 2014

matt1295 said:
We just had a huge down pour from no where so will answer that once it stops

Lightweight - I went out in the rain, at night, in the middle of winter and in my slippers to try and help you and your problem

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