Trailer wiring....ARRRGGHHH!!!!

[bustednutz]

OK maybe y'all can give a little insight.
I have a small 4x8 tow trailer that I run behind my Mazda 3.
I have a 4 pin flat connector that joins the car wiring to the trailer wiring.
ALL the lights and signals work except for the brake lights.

What gives? Bad ground maybe and its not getting enough juice to make them brighter?
Any ideas?

 

[Rand]

has the trailer worked previously?

I know the one I was pulling has no rear running lights so I thought something was busted... but it wasnt.

how is it wired? any kit or just taps?

 

[ChrisW]

With four pins I suppose I'm having a tough time seeing how it would provide for 5-functions, right signal, left signal, parking lights, brake lights and ground?

 

[Gotch]

4 pin fine for all those functions...make sure the running lights are not hooked up to the trailer brake light circuit...if these are reversed you won't see the brake lights due to them being on the "running light" filament of the bulb...

 

[EricG]

If you have a seperate turn signal bulb instead of a shared brake/turn bulb, you need an adapter!

 

[bustednutz]

Originally Posted By: EricG
If you have a seperate turn signal bulb instead of a shared brake/turn bulb, you need an adapter!


I believe thats my problem right there. Seperate amber bulbs for the signals.
I'll have to look into the adapter.

 

[supton]

See if you can get a "powered" adapter. You have to supply it with 12V (perhaps there is a cig lighter in or near your trunk?) but it then reduces the load on your brake lights. Some cars need them, others might not care -- I was told I "needed" it on my car, but, knock on wood, it has been ok with an unpowered one (bought the wrong one by mistake).

If you're worried about overload, as I was, you could put the parking lamps onto a non-switched 12V circuit, and just leave the parking lamps on all the time. I think that circuit has the most current draw (the most bulbs, usually two in the rear and two alongside, perhaps more), and it won't hurt anything to have it on all the time.

 

[wsar10]

hard to understand in forum form.....BUT, it sounds like maybe your depending on "running lights" wire (brown) for brake lights ??
If so your brake lights function from green and yellow along with turns.
either way go to the plug and get a "chassis" ground with a DVM and test the yellow and green wires under brake function, if they work there than follow it back until they don't, you should have your light fixtures them selves grounded as well.
you could also go to WM and buy a tester, it plugs directly into the trailer plug and has LED's on it that illuminate representing every function it's like $5 bucks.....

 

[Bladecutter]

Originally Posted By: bustednutz
OK maybe y'all can give a little insight.
I have a small 4x8 tow trailer that I run behind my Mazda 3.
I have a 4 pin flat connector that joins the car wiring to the trailer wiring.
ALL the lights and signals work except for the brake lights.

What gives? Bad ground maybe and its not getting enough juice to make them brighter?
Any ideas?



Need to have the correct brake light module to convert separate brake and turn signals into something that the trailer wiring can handle.

You could go to etrailer.com and look up the right unit for your Mazda 3.

BC.

 

[Donald]

Now if you were handy, 4 diodes would do the trick.

If you come across a 5 pin flat connector, the 5th pin is for backup lights and a surge solenoid.

 

[bustednutz]

Do any of you think I could tap directly into the 3rd brake light and run a wire for the trailer brake lights?

 

[exranger06]

Originally Posted By: bustednutz
Do any of you think I could tap directly into the 3rd brake light and run a wire for the trailer brake lights?

How is tapping into the 3rd brake light any different from tapping into the left or right brake light? Answer: it isn't. No, that won't work. A 4 flat connector has the following wires: 1 wire for the tail (running) lights, 1 for the left signal AND left brake light, 1 wire for right signal AND brake, and a ground. So you have 2 wires going to each trailer light (3 wires if you include the ground). The light bulbs themselves use the same filament for the turn signal and brake. If your car used the same bulb for brake and turn, it would be wired the same exact way, making wiring simple. But you need an adaptor, plain and simple. There is no other way to properly connect it.

 

[bustednutz]

Originally Posted By: exranger06
Originally Posted By: bustednutz
Do any of you think I could tap directly into the 3rd brake light and run a wire for the trailer brake lights?

How is tapping into the 3rd brake light any different from tapping into the left or right brake light? Answer: it isn't. No, that won't work. A 4 flat connector has the following wires: 1 wire for the tail (running) lights, 1 for the left signal AND left brake light, 1 wire for right signal AND brake, and a ground. So you have 2 wires going to each trailer light (3 wires if you include the ground). The light bulbs themselves use the same filament for the turn signal and brake. If your car used the same bulb for brake and turn, it would be wired the same exact way, making wiring simple. But you need an adaptor, plain and simple. There is no other way to properly connect it.


Bought one. Thanks for the advice everyone.