trailer lights behaving weird

Forums › Home Workshop DIY › trailer lights behaving weird - advice wanted.

CokemonZ

1047 posts

Uber Geek

#311499 21-Jan-2024 17:04

So I have a trailer with an aftermarket tow bar.

When the trailer is connected sometimes (mostly) the right indicator will not work, and inside the car it's going super fast.

Bulb is fine - sometimes works.

Wiring is ok I think, checked both plug and socket, and the wiring seems fine.

AFAIK the car is fine - I have previously used it with another trailer and it worked fine.

What should I look at?

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773 posts

Ultimate Geek

ID Verified

#3184819 21-Jan-2024 17:09

Are the trailer bulbs LED? if they are you will likely need to add load capacitors

https://www.geekzone.co.nz/forums.asp?forumid=141&topicid=265668

CokemonZ

1047 posts

Uber Geek

#3184820 21-Jan-2024 17:14

Good thought - no old school bulbs

gregmcc

2145 posts

Uber Geek

ID Verified

Trusted

Lifetime subscriber

#3184822 21-Jan-2024 17:22

Turn your right indicator on while parked, plug the trailer in an observe what happens, does the car blinker flash faster - if it does then there IS a wiring problem with the trailer, I would pick a rust/corrosion problem on the bulb contacts at the light on the trailer.

Failing that time to get under the trailer and look for damage.

tweake

2348 posts

Uber Geek

#3184823 21-Jan-2024 17:23

first thing for any weird lights on trailers is check the earths. common to have them rust and have a bad connection. also check you have an earth through the plug. sometimes people skimp and use the tow ball as an earth which leads to an erratic connection.

CokemonZ

1047 posts

Uber Geek

#3184825 21-Jan-2024 17:30

Has an earth, and its connected the whole way through.

That was where the internet steered me as well. Any way to test the quality of the earth?

CokemonZ

1047 posts

Uber Geek

#3184827 21-Jan-2024 17:32

gregmcc:
Turn your right indicator on while parked, plug the trailer in an observe what happens, does the car blinker flash faster - if it does then there IS a wiring problem with the trailer, I would pick a rust/corrosion problem on the bulb contacts at the light on the trailer.

Failing that time to get under the trailer and look for damage.

Does about 3/4 times.
I've had a pretty good look - cables underneath seem ok, no corrosion on bulb contacts.

I am thinking there is a crimped join under the trailer, maybe that's where the issue is

tweake

2348 posts

Uber Geek

#3184829 21-Jan-2024 17:36

CokemonZ: Has an earth, and its connected the whole way through.

That was where the internet steered me as well. Any way to test the quality of the earth?

connect trailer plug to car but do not put trailer on tow ball. use a meter to check resistance between car chassis and trailer chassis.

if earths are ok, as mentioned above check lamp sockets for rust. lights tend to get water in them and corrode the sockets. thats why led lights are so much better.

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tweake

2348 posts

Uber Geek

#3184831 21-Jan-2024 17:38

CokemonZ:

I am thinking there is a crimped join under the trailer, maybe that's where the issue is

i would not be surprised if there is a few joins. the most common failure is often the electrics and usually they are done to worse way possible. easy enough to rewire. try to put cable where its protected (ie inside cassis).

CokemonZ

1047 posts

Uber Geek

#3184837 21-Jan-2024 18:12

Yeah, I'm not likely to do that.
But if it's easy enough shouldn't cost too much.

CokemonZ

1047 posts

Uber Geek

#3184863 21-Jan-2024 18:30

tweake:

CokemonZ: Has an earth, and its connected the whole way through.

That was where the internet steered me as well. Any way to test the quality of the earth?

connect trailer plug to car but do not put trailer on tow ball. use a meter to check resistance between car chassis and trailer chassis.

if earths are ok, as mentioned above check lamp sockets for rust. lights tend to get water in them and corrode the sockets. thats why led lights are so much better.

Interesting, ok I'll do this.

Should I start the car or nah?

tweake

2348 posts

Uber Geek

#3184876 21-Jan-2024 18:56

CokemonZ:

Should I start the car or nah?

no need to.

k1w1k1d

1486 posts

Uber Geek

#3184878 21-Jan-2024 19:04

When checking trailer lights turn the tail lights on and leave them on while checking all the other lights.

If there is an earthing fault the trailer lights will go crazy when you turn the indicators or stop lights on. The only difference you should see with the tail lights is a slight dimming when another light comes on. This will be due to a bit of voltage drop in the trailer wiring. You have an earthing fault if any of the tail lights dim markedly or go out when another light comes on.

Does the left indicator work fine?

If your car has hazard lights, what happens when you use them?

What is make, model, and year of your car?

Flasher units are normally designed to flash at the correct rate for the number of lamps fitted to the vehicle. Adding a trailer, a blown bulb, or excessive current, etc can often alter the flash rate.

Many modern cars need a lighting module fitted when adding a trailer.

Wheelbarrow01

1710 posts

Uber Geek

Trusted

Chorus

#3184970 22-Jan-2024 04:01

Check the pins on the trailer plug. All the pins should have a split in the middle. Over time these splits close up, which can lead to a poor connection.
You can use a jeweller’s screwdriver to gently pry the pins open again (you probably only need 1mm or so) which will restore a solid connection to the pin sockets on the car plug.

CokemonZ

1047 posts

Uber Geek

#3184979 22-Jan-2024 08:15

Had a mate visit last night.
Works fine on his car, so think it must be something to do with mine.

Can't figure out how they got the cable to where it is, so going to take it to the place that installed the towbar.

MikeAqua

7769 posts

Uber Geek

#3185099 22-Jan-2024 12:31

If this was me, I'd get rid of those old school lights and put on a set of LEDs.

It probably won't solve this problem, but it will prevent future ones.

Mike

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