Strange issue with trailer indicator

Bryan

RMS Regular
Messages
10,022
Location
Tandragee
I cannot get my head around what's going on with my left hand trailer indicator. If I take out the bulb I'm getting the full 12 volt signal to the housing - as soon as I put the bulb in I loose the 12v feed. I'm getting 12v to the trailer connector on the back of the pickup ok. Anyone got any ideas what on earth is going on? It's not the trailer - I have another one that has LED lights and it doesn't feed the left indicator either.
 

Antoin

RMS Regular
Messages
7,280
Location
Portstewart
Drives
E60 535d
How is the wiring done in the car? Trailer or spliced on to the rear lights?

On some cars signal to the rear lights is pulsed and not a constant 12v. Sends trailer lights haywire
 
Last edited:

Bryan

RMS Regular
OP
Bryan
Messages
10,022
Location
Tandragee
It appears to be a proper wiring kit that plugs into the rear light connectors. It's a Ford Ranger pickup. It makes a buzzer in the cab when the indicators are working. I've even tried wiring a signal wire directly from the left indicator down to the correct pin on the trailer connector but it does the exact same thing.
 

Antoin

RMS Regular
Messages
7,280
Location
Portstewart
Drives
E60 535d
How is the wiring done in the car? Trailer or spliced on to the rear lights?

On some cars signal to the rear lights is pulsed and not a constant 12v. Sends trailer lights haywire

Meant to say trailer module
 

Odhran

RMS Regular
Messages
2,216
Location
Derry
Drives
A5 Sportback
Watching with interest. Passenger side trailer light intermittently doesn’t work on my tow car either
 

karl7900

RMS Regular
Messages
1,223
Location
Bangor, N.I
Drives
Touareg 3.2 V6
sounds like a poor earth connection
I was going to say this too. If you have another trailer handy, plug the lights into the pick up to see if fault is there still. If so, fault most likely with the pick ups wiring. If second trailer works ok, then check wiring on the faulty trailer.
 

Bryan

RMS Regular
OP
Bryan
Messages
10,022
Location
Tandragee
I was going to say this too. If you have another trailer handy, plug the lights into the pick up to see if fault is there still. If so, fault most likely with the pick ups wiring. If second trailer works ok, then check wiring on the faulty trailer.

As said above - same problem with both my trailers.
 

stevieturbo

RMS Regular
Messages
21,096
Location
Antrim
Drives
Old Ford
Earths would be first port of call...

Well with the exception of checking the trailer socket directly itself with a load plugged in. ie. not just a voltmeter
basically get a known good trailer board or full test plug or make something up.
 

Sham1

RMS Regular
Messages
133
The fact you have 12v with no load, and then it goes when a load is attached suggests a poor connection.take the cover off the 7 pin plug( or 13 pin) then plug it in and test from the indicator pin to the chassis of the vehicle, towbar is a nice easy spot. Do you still have 12v on the indicator pin? If no, then you are losing the positive signal, so check the wiring back to the light cluster. If you still have the 12v signal, then it’s an earth problem, so check that wire. Normally with an earth problem, the signal will return through some of the other wires, so you would see brake light and tail lights flashing etc. You haven’t mentioned this, and the earth is common to all other functions, so highly unlikely to be the earth. I would check the back of the socket first, then back to the light cluster. I worked at a 2016 ranger a few years ago and the wiring was very poor quality. the connectors are poor and let water into the cable which in turn just corrodes the cores.
 

roverspeed

RMS Regular
Messages
7,471
Location
Belfast
Drives
Insignia
I have fixed/replaced several sockets for friends and family over the years, and it's always the left indicator that goes first for some reason. Must be the poorest connector in the plug our most exposed etc. Change the socket would be my first port of call, pack of full of dielectric grease when you get a new one too!
 
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