trailer lights

OceanSprint

OceanSprint

Well-Known Member
Joined
23 Oct 2012
Messages
557
Visit site
I am wiring up my trailer, with a set of old lights, not labeled. Two questions

1. There seems to be 5 volts on both indicator lines when they are off and side lights on. Is this normal?

2. One bulb does both brake and side light. It has a double filament. A lower, coiled one and a higher, thinner straight one. Which is which?

Thanks for any help.
 
I can think of no reason there should be a voltage on a circuit when it is not in use. You may simpky have an accidental (poor) connection leaking voltage across from the sidelights. To identify which filament is which just power them up - the sidelight is about 5W and the brake light 21W, you'll easily see which is brighter.

Rob.
 
OceanSprint said:
I am wiring up my trailer, with a set of old lights, not labeled. Two questions

1. There seems to be 5 volts on both indicator lines when they are off and side lights on. Is this normal?

2. One bulb does both brake and side light. It has a double filament. A lower, coiled one and a higher, thinner straight one. Which is which?

Thanks for any help.
Click to expand...

1. Check for a poor earth connection. Thats what usually causes interactions between different lights on vehicles ...... and leads to an MOT failure. (If you owned a Renault you'd know about this!)

2. Just power the bulb up, one filament at a time. The bright one is the brake light, the dimmer one the tail light.
Or measure the resistances. The lower resistance of the two is the brake light.

You probably can't see which filament is connected to which contact anyway so knowing which is the thin one and which is the thick one is not a lot of help
 
Last edited:
Depends on your car. Some modern cars send a "sense" voltage through the system to check for bulb failure etc. However this is pulsed on the cars I know about rather than continuous, if you follow a recent landrover product towing a trailer/caravan fitted with LED lights you will see the lights pulsing unless the owner has fitted a very expensive Landrover LED adaptor (some resistors in a plug!)
 
It is new Chevrolet captiva and these odd voltages are from the car, without any plug in at all, so I think you are right. It has warning lights for just about everything, and then some, so could be the sense voltages you say. Thanks.
 
OceanSprint said:
It is new Chevrolet captiva and these odd voltages are from the car, without any plug in at all, so I think you are right. It has warning lights for just about everything, and then some, so could be the sense voltages you say. Thanks.
Click to expand...

I have just been testing the 7 pin socket on my new to me motorhome, Sprinter base, prior to picking up a car trailer. Trying with a lighting board, I can only get the brakelights to work. Testing with meter, I get 0.28v for indicators, and 4.7volts for L & R tail lights and brake lights, with no input. 14v for brakes when applied. Off the the Auto technician I think.
 
I bought a light bar from a motor parts supplier for my boat trailer many years ago. It was quite cheap ona plastic board about 1.5 metes long with all lights wired up to a long cable and plug. It also carries the number plate. Trailers are separately registered and insured here. The board is hung on the stern rail of the boat with boat on. Hung on the back of the trailer when boat is off and kept in the shed most of the year so protected. Now this works for the old style incandescent lamp systems and it probably would not work with a very modern LED car but I think was good value. That from one who loves wiring and has loads of cable lights etc to fit lights to the trailer. The only problem with the board is that is does not cater for side clearance lights. But then I never tow at night anyway. Of course the board is removed before the trailer goes in the water. I just have to remember.
olewill
 
You must log in or register to reply here.

Share this page

Top